Troubleshooting a JAP Special

[Rex]

Those different tappet settings  when doing the valve timing is a Velocette foible too.
I assume (though I've never given it much thought) that it stops the valve spring operation from affecting the valve timing measurements.
Incidentally, when I was fannying around with the valve timing on my Venom (the timing marks were wrong- another long story) someone more experienced than me said to set the valve timing up just rocking at TDC on the exhaust stroke as a good start, and he was right. It was as near as..
Clearly not satisfactory on a Honda, but for something designed in the 1930s it was OK.

[Rockburner]

Those different tappet settings  when doing the valve timing is a Velocette foible too.
I assume (though I've never given it much thought) that it stops the valve spring operation from affecting the valve timing measurements.
Incidentally, when I was fannying around with the valve timing on my Venom (the timing marks were wrong- another long story) someone more experienced than me said to set the valve timing up just rocking at TDC on the exhaust stroke as a good start, and he was right. It was as near as..
Clearly not satisfactory on a Honda, but for something designed in the 1930s it was OK.

Yes - I'd imagine that closing up the tappets would reset the timing to be a tad earlier (a degree or two), and the opening period a tad longer than when measured with the more open clearances... very interesting.

So - that described timing method is essentially setting the exhaust open time exactly right... and trusting that the rest are inline?  Makes sense if you've got a single, one-piece cam shaft where the entire thing is ground from a solid blank: if the first movement is correct, then it's a reasonable assumption that the rest of the timing is right because it can't be wrong (with a solid cam-shaft & cams).  If the engine has multiple cams, or the cams are individual parts slotted onto the cam-shaft:  then there's the opportunity for non-synchronisation.

[Rockburner]

Had a nice video call with the Guru yesterday, and learnt a few more useful things. 

Like: when checking the backlash it's best to do this with the timing chest cover fitted and nipped up! 
So - I did that, and:



I'd say that's as close to 1 degree as you're going to get!

The backlash between the timing pinion and camshaft is fine!  We had a conversation about the various options for the timing pinion - they were made with allowances for the backlash (-6, standard, +6, +12, etc, he's seen a -20!) and mine is a -6.  He initially recommended going up to a "standard" if I could find one, but after rechecking (properly!), it's all good, which is a bit of a relief because these things are just not made any more! If I was to find a 2nd hand one, I'd have no idea how worn it might be (which is the same issue with pretty much all the parts for these engines).

I'm also going to make sure that when I'm doing the valve-timing from now on I'm going to have the timing chest cover fitted and nipped up to ensure things don't have too much play: it makes more of a difference than I realised!


Obviously the guru does this so often, he actually has a cut-down cover with the timing pinion exposed so he can adjust it without removing the cover! Very handy, but massively overkill for me, once I've done this and got it as best I can, it won't be getting changed again.  The ignition timing on the other hand....

The guru reminded me of something else: the "critical" valve timing to get right is the Inlet Opening position.  Get that right and everything else will follow : the cams and cam-shaft and gear are all one solid piece, so if it's right in one place, it can't be "wrong" anywhere else, so I'll work off that principle.

We also discussed the bent push-rods, it's just something that happens - they're tubes, not solid.  I need to find some replacements, and we discussed sources. 
This is the worst one: Dial at 0

Dial showing the runout:


FYI: that's the crappy dial, I've discovered that the needle is a little loose and will wander over time. ffs.  It's ok for one-off measurements though.

The other rod isn't as bad, but best to replace the pair while I'm here:




He told me that apparantly one of the main suppliers tried to sell ally push-rod tubes a while back, which wasn't a good idea as they all bent!  The people who'd bought them were (understandably) pretty pissed off and complained bitterly, but he doesn't know if the company still sells them, or what they're made of: I shall investigate!

The current preferred material for race engines, running full power, is chro-moly tubing, but he reckons that I will be fine with regular steel tubing: I need to take the ends off my current rods (the ends are soldered on), and check the wall thickness, then go find some steel tubing of similar (or thicker) wall and see about making some up; well; presuming I can't find some ready made replacements somewhere else.

hey ho... do a job, make a job (as my ex used to say...)


Oh yeah - I also discovered last night that the classic bike track-day that I was sort of attempting to have the bike ready for has been moved to June or July, from May: so that "deadline" is no longer looming as heavily, phew.  What with the discovery of the fork and gearbox leaks I was thinking it wasn't going to be ready, now I still have a vague chance if I still want to aim for it.

[Rex]

Re new pushrods, couldn't you do that old trick of repurposing rods from another engine? Shorten and refix ends as required?
At least you'd know that the material was good for the purpose.

[Rockburner]

Re new pushrods, couldn't you do that old trick of repurposing rods from another engine? Shorten and refix ends as required?
At least you'd know that the material was good for the purpose.

It's a possibility to look into.

[Rockburner]

Bit of a delay there... sorry about that.  Normal service will hopefully be resumed soon.....
(3 weeks of delay due to another project, and since then I've had health issues: currently working around a trapped nerve in my neck which is doing weird things to my left arm and hand).

However - I manage to struggle through a bit of workshop tinkering yesterday, after fixing the Flymo again (the choke butterfly had fallen off the pin, luckily the screw fell into the airbox instead of being ingested!)

I was trying to get the valve timing set correctly. 
After a bit of pissing about and accidentally completely $%^&&ing up the cam-wheel positioning while looking at the timing pinion I decided to be a bit more systematic about things.

Firstly I identified each keyway on the timing pinion

If you look closely at that photo, you'll see that what I id'd as "2", had a couple of punch-pin marks over it.  However, when I took the bike apart, it was set at position "1", so I can only assume that the pin punches marks were from a previous owner/build.

Just another photo of the camwheel.


The timing wheel again


The dial guages over the valves.


After MUCH tinkering:
- set timing pinion on key
- fit case
- tighten nut
- rotate and check valve-opening times
- repeat rotation
- remove nut
- carefully remove case to prevent cam-wheel jumping ship
and repeat....

I ended up with this information :


Moving the Camwheel one tooth forward or backward compared to the timing pinion gives an adjustment of approximately 17degrees, which I did on the 3rd and 5th keyways after seeing that the initial reading was quite a long way out. (Hence 2 sets of readings for those keyways)

Compared to the desired timings:


It looks like actually - position 5 gives the closest to the aggregated correct opening positions. : Exhaust somewhere between 70 and 65 before BDC, and inlet somewhere between 45 and 44 before TDC.

Once I'd found that "sweet spot".... I marked it!!


I then wanted to get the nut done up tight on the timing pinion, but was struggling to hold the crank while I did so.
So, I went furtling in the draw of odd tools.... and dug up this:


One of Dad's home-made contraptions.  an old primary drive chain cog with a bit of tube bolted loosely to it. It's far less usable than it looks....

So,  I set about improving it.
I figured it would work a lot better if the rod were fastened properly across the cog in 2 places, so set about drilling a new hole in the cog 180 degrees across from the original.

Explain this....



Making progress:


I went through a few of the smaller drills simple because the case-hardened cog was tough to get through with a cheap wood pillar drill!

Eventually I got to the point of drilling the second hole in the pipe - which went relatively smoothly.

Found some bolts (M6 coarse, from the box of metric oddments), and had a lot of fun (not) searching for a pair of nuts (I spent about 2 hours in all during the day furtling through the selection of metric nuts for different jobs).

The tool fitted - but the output shaft itself sticks out from the splines, so I needed to remove some material from the pipe where it crosses the cog.

I initially started drilling again, until the inevitable happened:


So I thought $%^&& it.


I don't like angle-grinders, but they are good for making a mess.

The finalised tool in situ:


Engagement of the splines is approx 90% - that's good enough for government work.


And the Timing pinion is TIGHT.
It's actually a left-hand thread as well, so theoretically, as long as the engine is "pushing", it should be doing itself up...



Next things are to re-adjust the valve clearances back to 0.002" and fully finish the timing chest fit-out. 
I think I left out a spacer on the cam-follower shaft, they're moving about too much and "clicking" as the crank rotates - I think it's just the missing spacer (friggin well hope so!), then properly fit the Timing case cover with it's gasket. I need to re-read my notes just to check the assembly.

I've decided to live with the slightly non-perfect push rods for now, but keep looking for replacements. They're relatively easy to replace and will just need the rocker-adjustments redoing to reset the clearances when replaced, ie it shouldn't affect the timing (I believe).

I'll probably also fit the other outer covers that need gaskets next, just so they're done, before mounting the Mag and setting the ignition timing.

[Rockburner]

Decided to do today's write up while it's all still fresh.
Lots done today.

Priority was finishing off the Timing chest, so the first thing was a dry-assembly of the Timing chest including all the bits and the gasket;


Which seemed to be going well, until I spun the engine over and realised there was as distinct "click-clak" noise coming from "somewhere"...

ffs.

https://youtu.be/Gza5SEe7pGM

thankfully it wasn't coming from the crankcase....

https://youtu.be/UYPMI_8R3kQ

Primary suspect is the new inlet cam follower possibly clashing against something.

https://youtu.be/qz900MeY3sI

Here's a comparison of the old and new cam followers:


Not much of a difference visible there.. however:
The new one, left is significantly thicker than the old one....


There's also a touch more meat around the pin that holds the metal wheel.



So I tried the old cam follower (which is very, very tired)


I'm still getting the click-clak noises... they're just a touch quieter...

I also reassembled the cam followers with the extra spacer shim at the inboard end of the spindle they sit on, and weirdly I think it's helped a little.

I "think" the new follower IS clashing with the boss cast into the cases that supports the camwheel.  But I think putting the shim at the end is moving it enough to clear the boss, and (weirdly) actually putting the follower more central on the cam "path".

We'll see - I need to play with it some more.  I had a nice chat with the Guru, who was quite puzzled although he has had a similar experience in the past (at least it's not just me!)

We chatted about a few other things including the push rods and stuff.

Then I got on with the other thing on my mind: the Concentric carb.

I split it down for a clean:


BZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZT



While that was threatening the fuses I fitted the two lower casing covers.
This is the oil "outlet" fitting being prepped.
The Threebond is a nightmare, the tube has now got several holes in, and it's still runny as hell.



Messy


In the end I just poured the Threebond onto the newspaper and spread it thinkly with my finger!



Next, I pulled down an old G-clamp I'd liberated from Dad's workshop, I want it for a specific job and it needs some modifying...



THIS is what I want the clamp for:


To fit the push-rod tubes you have to hoik the push rods out from under the rocker arms, but there's not enough clearance, even with the adjuster wound right off.
With the clamp I can pull the arm up against the valve spring resistance and pull out the push rods.

So, happy with that.

I then progressed to the carb again.

Murky waters....


I messed around for a while fitting the carb top to the control cables: the springs on it are seriously strong, and this nerve issue I currently have has weakened my left hand enough to make things like that problematic. (I'm actually having trouble typing this...)

It's a good thing I had a cathartic session of ordering bits yesterday....


Chrome is for trailer-queens.

I bet the guy sold the carb because he couldn't get it to stop leaking.... Oh well - no matter, new Premier style float-chamber is en route already, along with a few more AMAL goodies.


So - next session will be trying to get to the bottom of the click-clak!

[Rex]

Just a suggestion for the click-clack.
I've noticed it on singles when they're being turned over slowly by hand that as it goes over the tip of the cam, the follower slaps down on the flank of the cam under valve spring pressure.
The days before quietening ramps and all that.

[Rockburner]

Just a suggestion for the click-clack.
I've noticed it on singles when they're being turned over slowly by hand that as it goes over the tip of the cam, the follower slaps down on the flank of the cam under valve spring pressure.
The days before quietening ramps and all that.

Yes - I am starting to think that may well be the cause, or at least part of the cause.

[Rockburner]

The Amal parts arrived today, so I snuck out into the workshop again!

Gaskets, float bowl, stainless allen screws, stay-up kit, and a nice mesh "trumpet"


So I started assembling the thing.

The "stay-up" kit is mostly material changes: the float is a military spec material that won't sink, and the mounting tangs are steel (the original part is entirely plastic), so you can easily adjust the float height just by tweaking the tang (phnar!).  The float needle is Viton tipped.


I was also going through all my Amal stuff, tidying it up and separating it out into relevant groups.  I decided to pack up all the Monobloc stuff into a box to be put into store.  I also had a load of random jets and needles from other carb types, so I put those safely away too.


The banjo from the Concentric was a tap rusty, so it got a good brassing.



The single feed fitting from the Monobloc fits the Concentric just fine, so I didn't need to buy another.



I have quite a few main jets.....


230 - 310, and a couple of outliers (140, 360).  I've decided to start with a 260 in the Concentric so I can then work up or down.


Mostly there:


Unfortunately it turns out the sodding needle clip is knackered - it's actually broken across the important bit, so I need to order a new one.
You can "just" make out the break.



So I then turned back to the investigation of the timing chest.

First I dropped the push rods out.


The idea being that I can see if the noise happens without any interference from the valve springs.
Like this I can hold the rod in place to provide "some" resistance.



Being a numpty, I accidentally undid that blanking bolt in the timing chest cover, DAGNABBIT!


Bloomin' thing.


So - to make it a little more secure, I added a springwasher


My investigations were pretty low in results tbh, I still can't quite figure it out, but the old exhaust side cam follower IS a little loose on the spindle, and the roller wheel IS a little loose on it's bushing.... so I may just have to bite the bullet and get another one.  Whether that slackness is enought to cause the clicking noise, I'm not sure, but its certainly a slackness that shouldn't be there.  It could be that with the valve spring resistance, it's causing movement of the cam follower that is making the clack noises.

There was a concern that the spindle itself might be worn, but the new cam follower seems solid on the spindle, so I think that's ok.

I also took some measurements of the push rods so I can look into buying some stainless tubeing to make new ones.
[/url]IMG_20260529_191941_407 by James Bridge-Butler, on Flickr



I think 1/32" wall thickness (info supplied from the Guru, who had a pair without caps fitted) is a mite thin, so I may try to get slightly thicker tubing if available.

The push rod ends are soldered on, so that's going to be a fun job swapping them over... yet more opportunity for conflagations!

Next time I try the timing chest I'm going to dribble some oil onto the cam follower spindle and the rest of the area, it could be that a layer of R is all it needs?

[Rockburner]

When was I last here... sheesh.... I need to pull my finger out.


So: I bought myself a new cam-follower.


And today I tried it out to see if it made any difference to that annoying "clickety-clack" noise I'm getting.

It didn't. (ffs)

However the follower DOES sit on the spindle MUCH tighter, so I'm going to use it. It also seems to fit nicely when the cover is on, ie the float of the cam-followers along the spindle is well within the desired tolerance (ie there's a tad of movement ), so I'm happy to use it.  Next job with that is to try assembly "wet", with some oil dribbled onto it.

I also want to file a notch into the lug of it - I noticed that one of the old followers has such a notch (see below), and what it does is allow oil to get onto the spindle.  There's no direct oil feed, the oiling is done by "splash".  Having said that - the cam-follower-spindle actually has a channel cut into the top of it, which I can only assume is an oil "trap" to keep the spindle lubricated.  Cutting a notch into the cam-follower-spindle lug will allow the oil that is splashed about to get into that channel, and from there it would lubricate the cam-followers on the spindle.  So - I kinda wonder why the followers don't have that notch as they come, but it is easily something that could be missed when making up a pattern part, especially as it could well be that (like my engine) only 1 of the followers in the engine the pattern maker had, had a notch.


Job for the next visit anyway, because while I was pondering the clickety-clack, I decided to have a go at refurbing/remaking the push rods.

First I took some highly accurate measurements, to ensure that I had the original lengths of the two push rods BEFORE I took the caps off.

(ahem ).



I decided to try "safe" heat first to remove the caps, I wasn't sure exactly how they were secured, the normal method is soldering, but the Guru told me that it's also perfectly valid to use epoxy, so these could be either.


This one was epoxied!


The other end was soldered! go figure!


Re-usable push-rod caps, steel.


Did my best to give everything a good clean up


New pipe on left... old on right.
These new ones should be a tad stronger by the looks of it!!

The new pipe came a tad long, 12", but that's cool


Precision marking for cutting (ahem)


And some hack-saw action


More high precision measurements....


Close enough for government work?


I always like to dress a hole nicely.... (ahem)


Using Meths to clean up the dust and dirt


The original plan WAS to try to solder the  caps onto the push rods, I promise you.  However... I never been good at soldering, but I did give it a try with a propane can (and yes, I DID burn my $%^&&ing finger tips, again), unsuccessfully... so err...

i cheated.


Trigger clamps for the win.


The second one was a bit of a bugger, for some odd reason the upper cap (the "cupped" one) refused to go onto the rod easily, no matter how much I cleaned up the pipe, or scrapped out the fitting on the cap.  In the end I just gave it a bit of a bash... 



They're roughly the same length, visually anyway.

To be fair, the "exact" length isn't terribly important, as long they fit between the cam-follower and the rocker arm within the range of movement of the adjuster on the rocker arm - there's at least 1/4" of play in there.....   And now I know how to do the job, I can disassemble them, file a bit more off the ends and re-glue them if they're too long.

While I was in the workshop I figured I'd also swap the oil feed fittings which I bought replacements for.

First I pulled the old, utterly knackered fittings off: using my "new" flare spanner found and bought specifically for this job!


Shiny new fittings installed!


I gave the feed tubes a clean while I was here.  They feed an oil dribble from the rocker box to the valve stem.


Fitted the dribble-tubes.


These are the old fittings for the dribble tubes, they're utterly shot.


As is the main inlet feed fitting, new one behind it with the oil feed banjo being tested.




A couple of these should fit..... (despite being metric!)


But.... and here's the rub.... the sodding main thread is wrong.


They're both 3/8" diameter thread, but the OLD one is 26tpi (and so BSC), the new one is 28 tpi... and I can't for the live of me figure out what that is supposed to be. It's not BSF, it's not BSW, it's not UNC and it's not metric (I don't think ? ).  So I may well be phoning the supplier tomorrow to find out just what tf it is!

Tune in next time for some lubed up action!

[cardan]

1/8" BSP (British Standard Pipe) is 0.383" major diameter, 28 tpi. (There's also BSPT which is a tapered version)

3/8" BSCY (British Standard Cycle) is 0.375" major diameter, 26 tpi.

Both are commonly found on pipe fittings on old British bikes.

Leon

[Rockburner]

1/8" BSP (British Standard Pipe) is 0.383" major diameter, 28 tpi. (There's also BSPT which is a tapered version)

3/8" BSCY (British Standard Cycle) is 0.375" major diameter, 26 tpi.

Both are commonly found on pipe fittings on old British bikes.

Leon

Interesting (I was hoping someone here would be more knowledgable about threads than I am, which isn't particularly hard I'll admit...)

In the BSP specs... what does the 1/8" measurement refer to?? because the outer diameter of the threads on the new oil-fitting is indeed as close to 3/8" as I could measure it.  So I'm confused slightly.

[Rex]

BSP confuses everyone. The belief is that it refers to the pipe I/D, but that's likely a myth, too.