classic motorcycle forum

Motorcycle Discussions => British Bikes => Topic started by: Billington on May 21, 2022, 10:34:36 PM

Title: She's hot
Post by: Billington on May 21, 2022, 10:34:36 PM
Today I took my 1932 BSA 500cc sv, out for the first time this year. After checking it over and adding fresh fuel it started on the second kick. I then went for a ride, after just under 2 miles the engine stuttered and can to a halt. The carburettor was very hot, hence the petrol had become so hot it vapour locked the carburettor. I let it cool down for 10 minutes and it started up again so I rode home.
I had is problem in 2019 when the air temperature was about 20 įC. The kind advice from this forum indicated that I needed to fit a Tufnol flange spacer, which I did. After fitting the 5mm spacer the bike ran okay in temperatures up to 28 įC. However the temperature today was only 16 įC.
I know what the problem is, its vapour lock. My question is why is it now happening at a lower temperature and is the only solution a thicker carburettor flange spacer?

(https://scontent-lcy1-1.xx.fbcdn.net/v/t39.30808-6/283354741_2777380682570884_1397522312361839763_n.jpg?_nc_cat=107&ccb=1-7&_nc_sid=730e14&_nc_ohc=zV8yCmaRHhUAX9hwv7z&tn=l5HYKvKabgt3rPoH&_nc_ht=scontent-lcy1-1.xx&oh=00_AT84o6W8XbAuS4jtH64HwVTItSDOm5SmdgXEN6aihj42sA&oe=628EEA85)
Title: Re: She's hot
Post by: cardan on May 21, 2022, 11:23:51 PM
Boiling the fuel at 16C is a bit of a worry - better start figuring why the engine is running so hot.

Worth a quick check on the valve timing (roughly ex closing and inlet opening at TDC on the non-firing stroke), ignition timing (roughly points opening at TDC on the firing stroke on full retard), and compression (if you can't stand on the ks at compression it should be close - don't let anyone tell you old bikes don't need compression).

I guess you're familiar with riding the beast, so giving it as much advance as it wants. After it's warm and before it's hot, will it take full advance and (almost) full air?

When it gives up, is the engine tight? If you lift the exhaust does it swing over freely on the ks?

Is the lubrication system working correctly? Plenty of oil and the tell-tale plunger (does it have one in 1932?) fully out?

The move on to air leaks or jet blockage in the carb, making it run lean. The colour of the plug should give a hint here - hopefully it's not white.

Final suggestion is to check the bike over bike mechanically for anything tightening up - gearbox, chains, brakes or wheel.

Have fun,

Leon
Title: Re: She's hot
Post by: Billington on May 22, 2022, 12:06:32 AM
Thank you Leon for all the things to think about, the bike was running okay when I stopped using it last autumn.
I checked the plug be for taking it for a ride and is was a light grey/brown.
I can kick the bike over okay and it has good compression, I need to use the lifter to get it over compression.
I run the bike with the air liver full closed it does not seem to make any difference open or closed, but I will try it open.
I run the bike with almost fully retarded, it seems to like it that way but I will try changing this again. Iíve heard that this can make the exhaust valve hot, is that correct?
No other part of the bike are hot.
I checked the contact breaker point gap before riding it was 0.008 inch however it should be 0.003, I will change this.
I also checked the inlet and exhaust tappet clearance are all fine.
The oil pressure was showing 6 psi which I believe is about right.
I did put a few drops of oil into the cylinder head before starting the bike to raise compression because I had not ridden the bike for 8 months.
The bike was not idling, if I closed the throttle the engine stopped.
Title: Re: She's hot
Post by: cardan on May 22, 2022, 03:48:47 AM
I run the bike with the air liver full closed it does not seem to make any difference open or closed...

I run the bike with almost fully retarded, it seems to like it that way...

I checked the contact breaker point gap before riding it was 0.008 inch however it should be 0.003...

OK, so the three things above are a worry - something is not right.

First, 0.003" for the points gap seems wrong - usually something like 0.012", so check for your specific mag before you do anything.

Related to this is the ignition timing, so set the points gap first. The bike should do almost all its running at full advance. There is a reason for this: the magneto is built (new, which yours is not!) to have its maximum strength spark when set at full advance. You might want to retard it a bit when you start the bike, but after that (barring a killer hill with hairpin bends) it should be full advance all the way.

So you need to set the ignition timing correctly - you probably have a handbook that tells you what is required for your bike? Probably about 35-40 degrees BTDC fully advanced.

Lastly the air lever. Again, most running should be done with the air lever full open. If not much happens when you move the lever, the first thing to check is that the cable is connected to the air slide. The air lever should take the air slide from fully closed to fully open - look into the mouth of the carb and make sure it is doing this.

If the slide is working, and the engine wants to run with the air closed, you have a problem with not enough fuel getting through the main jet. First check the number on the main jet (at the bottom under the needle) and compare with the specs. If it seems to be the correct jet, check that it isn't blocked, then check that the level of fuel in the fuel bowl is a couple of mm below the top of the jet.

When the main jet size and the fuel level are correct, the bike should like the air lever fully open for flat road running.

Any of these things - points gap, ignition timing, mixture - can cause the engine to run hot.

Leon
Title: Re: She's hot
Post by: cardan on May 22, 2022, 04:01:41 AM
Does the stamping on the carb say 6/112? If so, it is a 1" carb, not from a BSA but instead from a 550cc sv Ariel.

Not to worry, the carb listed for 493 and 557cc side valve BSAs of the period is a 6/014, also 1". Both the 6/112 and the 6/014 use a 150 main jet. Your main jet should have 150 stamped on it.

Even if it's not correct, the 6/112 will be perfectly fine. My guess is it may be a little longer between the slide and the flange than the 6/014.

Leon
Title: Re: She's hot
Post by: Billington on May 22, 2022, 06:23:02 PM
Hi Leon, thank you so much for the advice. You have given me a starting point for things to try. I will be working over the next two days, so on Wednesday I will try starting the bike by setting the throttle at about on eighth open and the air lever shut. Then move the ignition control to about half full advance. I will flood the carburettor by depressing the tickler for a short time only. As soon as start I will move the ignition control to fully advanced position, when the engine is warm I will open the air lever about three quarters of its travel. I will let you know how I get on after a test ride.
The carburettor details are as follows:
BSA W32-6 Carburettor
Type = Amal 6/112
No = 45A
Float Chamber 64/079
Jet =140 (Main Jet) B140)
Needle = 1
I set the Magneto timing by the BSA instruction book, however Iím not sure if these instruction work for both 1932 quality fuel and 2022 quality fuel.
I use regular petrol in my bike. If Iím honest I did not look at the E value when I purchased the petrol but I will have a look next time Iím filling up. I did however put about 25ml of Redex Lead replacement fuel additive. Iím not shore if this could have an effect.
To set the magneto timing I followed these BSA instruction.
Release the magneto pinion and set the piston at top dead centre of the compression stroke. The ignition is timed in the fully retarded position. With the piston at T.D.C and the ignition fully retarded I set the contact breaker points open .003 inch, then re-tighten the magneto pinion.
Thank you for any helpful contributions.
Title: Re: She's hot
Post by: Oggers on May 22, 2022, 07:55:27 PM
All useful advice - to which I would add mix. If it is a weak mix then any carburated engine can overheat quite easily. Personally I would clean the carb out thoroughly, check main jet (and size), needle position, clean out pilot air passages etc. Too close a tappet clearance on the exhaust valve can lead to overheating. I run mine slightly more than the recommended exhaust clearances. Rather obviously perhaps do check the lube oil feed and return. 
Title: Re: She's hot
Post by: R on May 22, 2022, 09:38:18 PM
To set the magneto timing I followed these BSA instruction.
Release the magneto pinion and set the piston at top dead centre of the compression stroke. The ignition is timed in the fully retarded position. With the piston at T.D.C and the ignition fully retarded I set the contact breaker points open .003 inch, then re-tighten the magneto pinion.
That all sounds a bit peculiar ?
And very likely the source of these troubles...

Is there a fully advanced ignition timing number (degrees/inch fraction) you can time the ignition to. ?
This is how most ignitions are timed.
And avoids all the vagueness of worn parts / things not within spec.

And, why open the air lever only three quarters open ??
If its running correctly, should be fully open ?
Title: Re: She's hot
Post by: cardan on May 23, 2022, 02:29:13 AM
Ah, fuel additives... I once tuned a four-cylinder FN for a guy, got it running nicely, rode it about 30km around the place, then gave it back to him for an upcoming rally with strict instructions on how to ride it. He was on the side of the road within 10km, and arrived at the regrouping stop with the thing running on about 2 cylinders. Of course I had to forego my cup of tea to look at it. The plugs were indescribable - it turned out he had filled the bike with 98-ocatane fuel and an additive of some sort. I just use standard fuel, with an eggcup of oil added in if really necessary.

A comment on the process of setting the timing with the points open 0.003": This was OK when parts were new, but with 90 years of wear it no longer guarantees that the points open 35 degrees before TDC at full advance, which is what is required. If the best position for the mag lever at 30 mph is not fully advanced (wire fully tight) the timing ignition is incorrect.

Leon
Title: Re: She's hot
Post by: Billington on May 23, 2022, 08:24:54 PM
I don't have a full advance timing number, sorry.

The bike was running fine before I removed all the fuel from both tank and carb, for storage. The only new variable is the new fuel and the fuel and Redex. On Wednesday I will try running the bike on full advance, if that does not work I may drain the fuel and try fuel from a different petrol station without adding Redex.
Title: Re: She's hot
Post by: R on May 23, 2022, 10:12:03 PM
In the meantime, I think you should try exploring where exactly that 'full advance is taking you.

I don't know this bike, but can you stick a pencil down the plughole, and get a feeling for when the piston is at TDC ?
If you put the traditional cigarette paper in the points, and the pencil down the plughole.
If you mark on the pencil when the paper is released, this gives an exceeding accurate indication of ignition timing.

I see that Leon mentions 35 degrees - is this for this exact model ?
Doesn't sound too far out of kilter.
Somewhere round the 1/4" to 5/16" perhaps.

It was also mentioned about giving the carb an exceptionally thorough clean.
It only takes a flake of rust blocking off a jet to upset the apple cart, mixture wise.
Title: Re: She's hot
Post by: cardan on May 24, 2022, 04:49:38 AM
I see that Leon mentions 35 degrees - is this for this exact model ?

No, but better than what it is now!
Title: Re: She's hot
Post by: Oggers on May 24, 2022, 08:13:31 AM
I mentioned cleaning out the carb as I encountered similar after a couple of my bikes had been laid up. The first instance was when I filled up the VB600 for the first time after winter lay up. Almost as soon as I left the filling station, the bike died and would not re-start. Fortunately I was not far from the house, so after an hour or so pushing the thing back into the garage, I stripped and cleaned the carb, replaced it, and it started first kick. It has been fine ever since. The second instance was again post lay up when the MSS just would not idle at all well. I blew out the pilot air passage and that seemed to cure it.

In both instances, I think a bit of crud from the tank had become dislodged over Winter, found its way into the carb, and messed things up. For sure it does not take much.       
Title: Re: She's hot
Post by: Billington on May 25, 2022, 09:21:07 PM
I went for a ride today to try the ideas suggested in this link (air temperature 10 C). My first ride I tried the air lever full open and the ignition half advance, however the results were poor, the bike did not get so hot that it vapour locked but is ran poorly an cut out on the one mile run.
In the afternoon I changed the oil and played with the throttle stop; I could set it a tick over but if I stopped the bike and started it again it would then stall on closed throttle which seems inconsistent. However I went for a 3 mile ride (air temperature now 17 C), with the air lever closed (because I had forgot to open it!) and trying different ignition positions as the road dictated (I live in a very hilly area of England). The bike did not stall because I was managing this with the throttle. At the end I could touch the carburettor but it was still warm.
Thank you for all your advice and questions.
Title: Re: She's hot
Post by: Rex on May 25, 2022, 10:52:26 PM
If you ever get to the stage where you can't touch the carb then there's big problems somewhere. It passes X cubic feet of air a minute which keeps   it cool, and if it's hot to the touch then it needs further investigation.
Title: Re: She's hot
Post by: R on May 25, 2022, 11:29:53 PM
Not only is it passing x cubic feet of air per minute, its vapourizing the fuel into the airstream.
Most cars have heated manifolds, to prevent carburettor icing from this.

I once had a split water hose which forced a rejig to the heating to go elsewhere,
and the result was carburettor icing HELL - the carb would ice up, block off the flow,
the engine would cut out, freewheel for a while, the blockage would melt,
and the whole process repeat. You wondered if it was going to get home.
(It was a damp day.)

I note the above mentions only half advancing the timing.
This means its running with retarded timing.
Most engines hate this, it can leading to overheating most promptly.
Riders really need to control this function quite diligently.

Not fully opening the air lever means its effectively running with the choke part/half on.
Most engines hate this, and will chuff black smoke and carry on.
Riders really need to control this function quite diligently.
Title: Re: She's hot
Post by: cardan on May 26, 2022, 03:55:02 AM
Hi Billington,

I see - here and on the BSA forum - that your starting/running/gutlessness/overheating problems with this bike have been going on for some years. You don't deserve that!

A 1932 500 sv BSA should be completely reliable, pull like a train, and not overheat until it gets to 38C outside. It should cruise comfortably at 40 mph. However to make it like that - assuming all the mechanicals are good - it has to be properly tuned and maintained. No amount of random fiddling with the controls will make the bike run nicely if the valve timing/tappet clearances/ignition timing/points gap/carburettor settings are incorrect.

My number one suggestion would be to get a knowledgeable person to help you. If you bring it to my place (in Adelaide Australia!) I'll help you tune it, but is there anyone closer? This is really hard because the are lots of "experts" out there, but you need to find someone who understands old motorcycles and can do the work. Tricky these days.

Failing that, you CAN do it yourself. But you have to be systematic, and work through the issues one at a time.

Maybe start by being CERTAIN that the magneto points gap is set to about 0.012" fully open, and that the points open about 35 degrees before TDC (piston say 3/8" or 10 mm before TDC on a longstroke bike like the BSA) when the lever is fully advanced (tight wire). When you're certain of this, retard the lever fully and you will hopefully find that the points have just opened (maybe the promised 3 thou) at TDC.

Once completely confident that the ignition timing is right, you can run the bike at full advance - no fiddling - and move onto the next things... (in order - loosen the tappets to say 10 thou so there is no chance of them closing up while running, check that the valves are rocking - exhaust closing and inlet opening - at TDC on the non-firing stroke, clean the carb, check the main jet size, check the needle, set the idle mixture screw to a best guess - all the way in then 1 1/2 turns out from memory - fit a new Champion D16 plug, fresh fuel in the tank...)

Good luck,

Leon
Title: Re: She's hot
Post by: Oggers on May 26, 2022, 09:19:46 AM
I think you are masking the root cause of the problem by fiddling with the air lever and throttle, and observing air temperature. You need to be far more methodical in your approach. A 500 SV BSA is a pretty numb thing, not too disimilar to my VB600, and there are not an awful lot of variables which would give you the problems seen. If it was running fine last time around, then my bet is still on muck in the carb - so clean it out. After that, think of things which have happened since which could possibly affect the running of the bike. Therefore - clean the points, consider introducing fresh petrol, and fix any air leaks which could have developed since - particularly at carb intake flange - as a lean mix will make the bike run hot. Failing that, then do as Leon suggests. Points gap, tappets, timing etc.     
Title: Re: She's hot
Post by: Billington on May 26, 2022, 10:07:10 PM
Part of the problem is that the ignition advance/retard lever does not stop in position I have turned it to. It slowly returns to closed which equates to full retarded. The friction available on the lever does not seem able to overcome the spring in the magneto.
Title: Re: She's hot
Post by: Rex on May 26, 2022, 10:14:11 PM
Is the Belleville washer missing then? It's a bit pointless if it doesn't stay where it's put.
Title: Re: She's hot
Post by: Billington on May 26, 2022, 11:15:24 PM
Part of the problem is that the ignition advance/retard lever does not stop in position I have turned it to. It slowly returns to closed which equates to full retarded. The friction available on the lever does not seem able to overcome the spring in the magneto.
Title: Re: She's hot
Post by: cardan on May 26, 2022, 11:31:57 PM
As Rex suggests, there should be a belleville washer (conical) or a wave washer (wavy!) between the top plate of the lever (which should be fixed to the boss so it can't rotate) and the lever itself. The nut/screw on top is meant to control the friction. If your washer is missing or tired, you'll have to find a new one. In the meantime, you can cut a washer or two from cardboard (cereal packet maybe).

Leon
Title: Re: She's hot
Post by: R on May 27, 2022, 11:07:03 PM
And/or take it apart and degrease all the components then.
Sounds like what is missing is friction ?
Title: Re: She's hot
Post by: Rex on May 28, 2022, 08:46:32 AM
That would be curing the symptoms rather than the fault. When assembled and working correctly they still need grease to give a smooth action.
Title: Re: She's hot
Post by: Billington on May 29, 2022, 08:45:10 AM
Iím a little embarrassed to tell you this, however the reason why the ignition lever would always return to retarded was because the nut had worked lose, after tightening the nut I can run on constant full advance. I had previously identified that this nut would work lose so had put some lock wire around it to stop it turning, however over time the lock wire around the nut was insufficient. When I first realised this I thought that I had finally found the solution, but Iím afraid Iíve only found part of the puzzle, because after riding four miles on full advance at 17 C (air temperature) the bike was so hot that smoke was coming from the cylinder head. So itís not the ignition timing.
Should I take the cylinder head off an look for heavy carbon deposits, could it be that I need to decarbonise my bike, would that make it run so hot? 
Title: Re: She's hot
Post by: cardan on May 29, 2022, 09:11:13 AM
OK, but you need to understand that having the lever set to full advance doesn't mean that the timing is correct. Plenty of good advice laid out above.

Leon

Title: Re: She's hot
Post by: Billington on May 29, 2022, 04:45:58 PM
My thinking has moved on to the point people have been making  about weak fuel mixture and leaks at the head gasket. I had checked and tighten the cylinder head bolt as part of my spring service notes after taking the bike off the road in the autumn, but I now realised that I had set my torque wrench to 30 newton meters, but my notes state 30 foot pounds, which would equate to 40 newton meters.

When I stopped the bike yesterday smoke was coming out of the head gasket, which would indicate that is not hermetically sealed, there was also a shiny oil mark on the cooling fins that come from the cylinder head. All this would point to the cylinder head not being completely airtight. If smoke can get out air can get in during the intake stroke.

I will set the cylinder head bolts to their correct torque setting and see if this makes a difference. If it does not I will remove the cylinder head anneal the copper gasket again and refit the cylinder head.
Title: Re: She's hot
Post by: R on May 29, 2022, 10:29:45 PM
You will also need to check exactly where your ignition timing is at some point !
Title: Re: She's hot
Post by: cardan on May 30, 2022, 12:48:15 AM
In the photo at the top of the page it's clear that the engine is cooked. Literally. You can't repeatedly ride an old bike until it stops from overheating and expect it won't expire permanently at some stage. Unfortunately, as we've said before, no amount of random fiddling with controls will make this bike work. Clean it, tune it, repair whatever needs repairing, then enjoy it.

If you're not prepared to to work your way systematically through the issues, or get someone to do it for you, it will never run correctly and you might be better selling it. Pity, as it's a nice old bike.

Leon
Title: Re: She's hot
Post by: Billington on May 31, 2022, 12:35:02 PM
Yesterday, I tightened the cylinder head bolts to 30 foot pounds, then set the engine at TDC using a gauge I made from a wire coat hanger. After this  I set the contact breaker points gap to 0.003 with the ignition fully retarded, these are the instruction in the BSA book for my model.

Today I went for a half mile ride; I stopped early because it had started to rain hard; however I could see smoke coming from the cylinder head again. Hence the next thing I intend is remove the cylinder head anneal the copper gasket and use Wellseal to improve the seal.

I will take photos of the head and post them.

Thanks again for your advice.
Title: Re: She's hot
Post by: Billington on May 31, 2022, 06:49:52 PM
The pictures with this post are as a result of me taking the cylinder head off today, because it was leaking smoke which was not solved by tightening the head bolts. Also the bike is running hot possibly due to the air fuel mixture being lean due to the air being drawn in past the cylinder head gasket.

Pictures

1, The spark plug with a light brown indicating hot or lean
2, Contact breaker when the piston is at TDC. The point gap is 0.003 in this picture. This has been set in accordance with be information given by BSA for this bike.
3, Copper head gasket before cleaning. You can see the black marks at the top and bottom of the gasket where smoke was coming out.
4, The Copper head gasket after being cleaned with a Brillo pad, scotch brite and annealed.
5, Cylinder head before cleaning. You can see the shiny marks where smoke was escaping.
6, Cylinder head after cleaning.
7, Piston and valves before cleaning. Again you can see the shiny marks where smoke was escaping.
8, Piston and valves after being cleaned with a Brillo pad, scotch brite.


(https://scontent-lcy1-1.xx.fbcdn.net/v/t39.30808-6/285550733_2784230041885948_2004379972179408339_n.jpg?_nc_cat=100&ccb=1-7&_nc_sid=730e14&_nc_ohc=kgEahhfweGMAX_6YTo0&_nc_ht=scontent-lcy1-1.xx&oh=00_AT_M86D_ypgItVJR8t-v3zK5We0YrpMnV2gvJwfxxOrA2A&oe=629C2B83)
Title: Re: She's hot
Post by: cardan on June 01, 2022, 12:30:00 AM
Hi Billington,

Given that you have ignored most of the good advice put to you so far, it's tempting just to ignore your problems and leave you and the BSA handbook to it.

So ignore advice again if you like, but if the rubbing block on your points is that far past the ramp to get the points to open 0.003" something is wrong. Probably the rubbing block is worn (have I said that before?). Have you set the points gap to 0.012"? Looking at the photo, it's hard to imagine that the points will open much more since the ramp looks well past...

No doubt your handbook tells you to give the valves a light grind while you've got the head off.

Leon

Title: Re: She's hot
Post by: john.k on June 01, 2022, 03:36:46 AM
The ignition advance should be about 1/2" ,maybe max at 5/8"...........I have several 500sv s and all have 1" Amals with a 160 or 170 mainjet.......other point is the BSA has a gear drive mag......lots of scope for getting false settings from backlash in the gears........the old maxim.....turn back 1/2 turn,then turn in direction of rotation to the BTDC desired....check timing and point opening.........my 1934 BSA 500 OHV has a Miller Magneto......these had a bad name ,but IMHO mainly for the failure of the tiny chain drive to the dynamo.
Title: Re: She's hot
Post by: iansoady on June 01, 2022, 11:36:28 AM
I can't see any pictures - is it just me?
Title: Re: She's hot
Post by: Billington on June 01, 2022, 02:00:25 PM
Hi Ian,

Not being able to see the images is an issue at your end, other can see them. Try updating your web browser, or using a different web browser.
Title: Re: She's hot
Post by: iansoady on June 01, 2022, 03:59:52 PM
I'm happy with my browser so will just have to forgo the pleasure of seeing them.
Title: Re: She's hot
Post by: R on June 01, 2022, 11:15:33 PM
Pic should be clickable ?
https://scontent-lcy1-1.xx.fbcdn.net/v/t39.30808-6/285550733_2784230041885948_2004379972179408339_n.jpg?_nc_cat=100&ccb=1-7&_nc_sid=730e14&_nc_ohc=kgEahhfweGMAX_6YTo0&_nc_ht=scontent-lcy1-1.xx&oh=00_AT_M86D_ypgItVJR8t-v3zK5We0YrpMnV2gvJwfxxOrA2A&oe=629C2B83 (https://scontent-lcy1-1.xx.fbcdn.net/v/t39.30808-6/285550733_2784230041885948_2004379972179408339_n.jpg?_nc_cat=100&ccb=1-7&_nc_sid=730e14&_nc_ohc=kgEahhfweGMAX_6YTo0&_nc_ht=scontent-lcy1-1.xx&oh=00_AT_M86D_ypgItVJR8t-v3zK5We0YrpMnV2gvJwfxxOrA2A&oe=629C2B83)

The only one of any real interest is the points.
Which as Leon sez looks like .003 is about as open as they will get.
Makes you wonder where the timing is ??
Title: Re: She's hot
Post by: chaterlea25 on June 01, 2022, 11:40:44 PM
Hi All
From the photos it looks like the head gasket was / is  leaking badly
This is a major cause of overheating
Get the head checked for flatness, or rub on a thick sheet of plate glass with some grinding paste
I would think that the head gasket will be damaged / thickness varying ?
Make sure all the head bolts thread easily and fully into the cylinder and are not bottoming out when the threaded in fully
As R posted the points should be almost fully open at the pictured position

John
Title: Re: She's hot
Post by: cardan on June 02, 2022, 07:30:47 AM
2, Contact breaker when the piston is at TDC. The point gap is 0.003 in this picture. This has been set in accordance with be information given by BSA for this bike.

Hi Billington,

I wonder if you misunderstand the ".003" at TDC at full retard" message from BSA.

I think you have been doing this: You set piston to TDC, set the lever to full retard, then adjust the points to 0.003". Correct?

But this is not what BSA meant. Not at all.

Let's separate this into two parts: 1. Setting the points gap, and 2. Timing the magneto to the engine.

1. Setting the points gap. Imagine the magneto is out of the engine and on the bench. For it to give a nice spark when rotated, the points have to be adjusted to a gap of 0.012" (12 thou) when the points are fully open. Looking at your photo of the points, the points rotate clockwise (the fibre block that runs on the cam ALWAYS trails), so from where they are in the photo at about 2 o'clock until they close at about 10 o'clock the points gap should be about 12 thou. So, set the gap to 12 thou, but it doesn't matter too much if it wobbles a few thou as you rotate fro 2 to 10 o'clock.

OK. This is what the magneto man does when he renovates your magneto, at his place, when it's not attached to your bike. The points gap should not be touched again until wear causes the gap to change.

Now the magneto man spins the mag and there is (hopefully) a huge spark at full advance (the tight wire rotates the cam towards the rubbing block so that the points open earlier), and a slightly less intense spark when the magneto is retarded (loose wire, cam rotates away from the rubbing block, so spark is later).

All done. The mag is working fine. Don't touch the points. Next we have to time the magneto to the engine. Because the spark is best at full advance (tight wire), the plan is to have the best spark where the engine spends most of its time - at a few thousand rpm when the spark needs to occur at something like 35 degrees before top dead centre, which corresponds to the piston about 9.6mm before TDC.

Now there are TWO WAYS to set the magneto timing that will give the same result: the first is to set the points to open 35 degrees/10mm BTC with the magneto at full advance, OR the BSA method to set the points to be 0.003" at TDC with the magneto at full retard. BSA are saying the the points are just starting to open - by 3 thou on their way to 12 thou - as the rubbing block is sliding up the ramp on the cam. When the magneto was new, these two methods should give the same result, so if the first method is used, and the magneto is fully retarded and the engine is rotated to TDC the points with have opened 0.003", and vice-versa.

The first method is better in 2022 because stuff has worn, been replaced or fiddled-with in the 90 years since the bike was made, and the important thing is that the spark occurs 35 degrees/10mm BTDC at full advance. The BSA method is easier but indirect, and in 2022 could easily give the wrong ignition timing.

So...

2. Setting the magneto timing. If the mag was fresh back from a rebuild (with its points set to 12 thou), the drive gear would not be attached to its taper. You would fit the mag to the bike, set the engine to 35 degrees/10mm BTDC on the firing stroke (both valves closed) (always approach by rotating the engine forward because of backlash in the timing gears), set the mag to full advance, rotate the magneto until the points are just beginning to open, push the gear onto its taper, and do up the nut.
(The BSA version would be set the engine to TDC on the firing stroke (both valves closed) (always approach by rotating the engine forward because of backlash in the timing gears), set the mag to full retard, rotate the magneto until the points are just opening by 0.003", push the gear onto its taper, and do up the nut.)

Now here is my suggestion for how you set your spark from where you are now:

1. Adjust the points gap to about 12 thou, on average for the time the points are open.

2. With the head off, go to TDC on the firing stroke (both valves closed as you go either side). Measure the position of the top of the piston relative to the barrel. Rotate the engine BACKWARDS by half a turn or so, then bring it slowly forwards until the piston is 10mm lower that it was at TDC.

3. Take off your timing cover, and have a look at what you've got there. Between the inlet cam gear and the magneto gear, I think there's a larger idler gear? I think this can be slid out? If so, take it out.

4. Set the magneto lever to full advance. Rotate the magneto so that the points are JUST OPENING - i.e. the rubbing block is just impacting on the cam ramp and causing the points to crack open. Hold the points there and see if the idler gear will drop back in. It will probably be out by some fraction of a tooth (hopefully not exactly half a tooth!) so drop it in on the nearest tooth. You should be able to get the points to open somewhere around 10mm BTC - say 1mm either way. If there are 40 teeth on the magneto gear, one tooth will change things by 9 degrees.

5. Button it up. Done.

6. Ask if you don't understand.

Leon

Title: Re: She's hot
Post by: iansoady on June 02, 2022, 10:26:44 AM
Yes, can see them via the link.

That's a very well thought out and complete response from Leon. If you follow it you're much more likely to succeed.
Title: Re: She's hot
Post by: Billington on June 03, 2022, 10:32:00 PM
Leon, thank you so much for your detailed response, I really appreciate your time and effort to share your expertise on old bikes. Iíve printed off your response and placed it in my BSA ring binder.

Before reading your response I completed my top end overhaul, which included torqueing the head bolts several times, when cold and after running the bike to get it warm. The bike now seems to be air tight at the cylinder head. On my 3 mile ride today it is now pulling strongly up the hills where I live, however this was not long enough for me to satisfy myself that Iíve completely resolved this issue. If the problem of overheating continues to happen I will follow the steps you have outlined.

There are other issues Iíve been working on with the advice from you and others such as how to ensure the ignition lever has enough friction to stop where Iíve put it, currently I ride the bike with one finger rapped around the ignition lever, which results in hand cramp after 10 minutes. Also getting it to idle just right, but these are all problems I will persevere with overtime.

Thank you again for any ideas and advice you may have given.
Title: Re: She's hot
Post by: R on June 04, 2022, 02:23:43 AM
If the ignition timing is not right, could be the reason it blew that head gasket.

And if that ignition timing is still not right, future problems you might ? see is a part
molten piston coming out into the exhaust pipe, or the big end giving up the ghost. !!

Trusting to blind luck without any science to it is not really a plan for long-term ownership ...
Title: Re: She's hot
Post by: cardan on June 04, 2022, 03:44:30 AM
Hi Billington,

Sorry, but if you're riding the bike without setting the points gap and the ignition timing, you're nuts. What is the point of printing the instructions if you don't intend to follow them? I don't get it.

Leon
Title: Re: She's hot
Post by: john.k on June 04, 2022, 05:53:20 AM
I think BSA used to quote the 003 dimension as that was the thickness of a cigarette paper,ie set the points to just dragging on a paper as it was pulled out.......on account of no one could afford feeler gauges in the depression.......the thickness of a business card at 012 was also a commonly quoted dimension.
Title: Re: She's hot
Post by: Oggers on June 10, 2022, 07:55:50 PM
Leon

I fear we are all urinating in the wind. Your replies have been hugely comprehensive and extremely well informed but the chap is clearly somewhat oblivious and insensible to them. Riding the bike with a finger wrapped around the advance/retard lever to stop it moving seems pretty conclusive to me how the chap thinks - or perhaps doesn't.....     
Title: Re: She's hot
Post by: cardan on June 11, 2022, 05:27:15 AM
Thanks Oggers. I live in hope that Billington will get some help to tune his BSA (hopefully incorporating the advice above) and report back on the transformed running of the bike.

Leon
Title: Re: She's hot
Post by: john.k on June 16, 2022, 11:43:28 AM
heads warped badly by repeatedly tightening down on a knackered head gasket are pretty common on sidevalves too.......better to flatten the head ,discard the gasket,and apply silastic to seal the tiny gap left......works very well.
Title: Re: She's hot
Post by: 33d6 on June 17, 2022, 02:59:47 AM
I wouldn't worry too much. He's over on another forum going through the same story. Nothing like forum hopping until you find an answer you like.

Of course I could be quite wrong. There could be two owners of  an early 30's 500 sidevalve BSA out there, both with the same story.

Cheers,
Title: Re: She's hot
Post by: cardan on June 17, 2022, 03:13:25 AM

The Death of Expertise.

"... Today, everyone knows everything: with only a quick trip through WebMD or Wikipedia, average citizens believe themselves to be on an equal intellectual footing with doctors and diplomats. All voices, even the most ridiculous, demand to be taken with equal seriousness, and any claim to the contrary is dismissed as undemocratic elitism..."

https://www.amazon.com.au/Death-Expertise-Campaign-Established-Knowledge/dp/0190469412

Leon
Title: Re: She's hot
Post by: Rex on June 17, 2022, 01:33:12 PM
Someone I know well said that I ought to do some research before having the Covid jab, and then some more on why Russia had every reason to attack the Ukraine.
He couldn't see that "doing some research" doesn't really mean shouting into a Net echo chamber to reinforce the dumbarse opinions you already have, unlike the research carried out by gov'ts, drug firms, drug agencies etc etc to develop new products and drugs which starts on an unbiased baseline and is done by true experts in their field.
 As the post above says, so many self-styled experts now in every field of human endeavour.
Title: Re: She's hot
Post by: R on June 17, 2022, 11:57:19 PM
I'm not saying I agree or disagree with any of this.

But we all know what an 'expert' is, right ?
X        = an unknown quantity.
spurt = a drip under pressure.
So an expert is the unknown quantity of a drip under pressure !
?????

There certainly are varying levels of expertise though ....
Title: Re: She's hot
Post by: john.k on June 18, 2022, 06:28:42 AM
Better on a forum than giving me GBH of the earhole with all the dumb details of how they are going to make their 1935 sidevalve do 80mph....being in a vintage bike club now you got the choice of millenials destroying old bikes,or old gits telling you about their most recent and most  gruesome bowel ailment.
Title: Re: She's hot
Post by: R on June 18, 2022, 07:40:23 AM
And as someone unfamous once said, anything that goes wrong with
your pride and joy can be fixed, with a mere wad of $$$ ...
Title: Re: She's hot
Post by: Rex on June 18, 2022, 08:45:25 AM
Better on a forum than giving me GBH of the earhole with all the dumb details of how they are going to make their 1935 sidevalve do 80mph....being in a vintage bike club now you got the choice of millenials destroying old bikes,or old gits telling you about their most recent and most  gruesome bowel ailment.

Very true, and then there's the third type, the one who has a 1932 Grindlay Big Balls, bought in bits in 1963 and untouched since, though he's going to get started on it "soon, before I get too old".
And he's 87 now...
Title: Re: She's hot
Post by: R on June 18, 2022, 10:48:35 PM
Don't knock it, thats saved 97% * of old bikes from oblivion.
* figure plucked at random from the sky.

Motorcyclists tenacity in holding on to worn/knackered/obsolete/past it bikes is legendary.
Although a heck of a lot of 'collectors' of about nearly everything mechanical show this trait ?


Title: Re: She's hot
Post by: john.k on June 19, 2022, 04:36:15 AM
here s something you wont believe...i recently sold some land...and the new owners didnt want the 50odd tons of mechanical collectables stored there......they could have had a head start on an awsome collection.
Title: Re: She's hot
Post by: R on June 19, 2022, 10:55:57 PM
Ha !
I've been to enough farm clearing sales to know that the scrap man makes a tidy living from
snapping up old 'collectables' - about anything metal falls into this category.
And that was before the price of scrap steel skyrocketted.

We are getting well away from ailing old BSA's though.
Title: Re: She's hot
Post by: Oggers on June 20, 2022, 02:55:16 PM
Leon

It is far more than the death of expertise. It is the death of rational, evidence-based thinking and a prevalence to melodramatic knee-jerk reaction based on nothing but the (a)moral inclinations of the individual. We have become a country of emotional incontinents. The British stiff upper lip has gone forever.     
Title: Re: She's hot
Post by: iansoady on June 20, 2022, 05:33:28 PM
Much as I'd like to agree, I don't think rational evidence based thinking has ever been the norm. Sadly, most people have always relied on prejudice and received opinions. Which of course are much more readily available these days.
Title: Re: She's hot
Post by: R on June 21, 2022, 07:45:36 AM
Beam me up Scotty ....
Title: Re: She's hot
Post by: Rex on June 21, 2022, 08:49:12 AM
Sadly, most people have always relied on prejudice and received opinions.

But of course "your" opinions are received and prejudiced, while "mine" are considered and researched.
Title: Re: She's hot
Post by: Oggers on June 21, 2022, 09:12:40 AM
Ian

To an extent I agree. It was indeed never the norm for many folk. However, it was there nevertheless, usually prevelant in those with influence and power, and until a couple of decades ago prevented the slide into histrionic oblivion we all must endure today.
Title: Re: She's hot
Post by: john.k on June 29, 2022, 06:56:34 AM
You must get with the times ..Its now called "Mansplaining"........as you might have guessed,thats where an older male is telling millenials what to do...Particularly abhorrent to 30 something wimmin.
Title: Re: She's hot
Post by: Oggers on July 04, 2022, 11:38:49 AM
Many 30 something wimmin are all to keen to interpret simple explanation or advice as being told what to do. Invariably it is not the man being patronizing, rather the woman being deliberately over-sensitive using any excuse to take offence in order to denigrate the man. To me, it is a deeply abhorrent trait and is one of many reasons why I simply avoid such folk in these psychologically disturbed times.   
Title: Re: She's hot
Post by: john.k on July 14, 2022, 08:52:02 AM
Saw good one t'uther day online somewhere.....anyhoo ,boss is interviewing,offers millenial the job,as she is the only one came to interview.........he says ,OK ,you ve got the job Ill see you at 8am sharp tomorrow morning......She ..OMG,you are coming into my house  tomorrow morning !