Author Topic: She's hot  (Read 1687 times)

Offline Billington

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Re: She's hot
« Reply #30 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.



Offline cardan

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Re: She's hot
« Reply #31 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


Offline john.k

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Re: She's hot
« Reply #32 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.

Offline iansoady

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Re: She's hot
« Reply #33 on: June 01, 2022, 11:36:28 AM »
I can't see any pictures - is it just me?
Ian
1952 Norton ES2

Offline Billington

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Re: She's hot
« Reply #34 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.

Offline iansoady

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Re: She's hot
« Reply #35 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.
Ian
1952 Norton ES2

Offline R

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Re: She's hot
« Reply #36 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

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 ??

Offline chaterlea25

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Re: She's hot
« Reply #37 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

Offline cardan

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Re: She's hot
« Reply #38 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

« Last Edit: June 02, 2022, 07:35:00 AM by cardan »

Offline iansoady

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Re: She's hot
« Reply #39 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.
Ian
1952 Norton ES2

Offline Billington

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Re: She's hot
« Reply #40 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.

Offline R

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Re: She's hot
« Reply #41 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 ...

Offline cardan

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Re: She's hot
« Reply #42 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

Offline john.k

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Re: She's hot
« Reply #43 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.

Offline Oggers

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Re: She's hot
« Reply #44 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.....