classic motorcycle forum

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.

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.

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.

Aaaand I got into the workshop today as well!

I spent some time reading Fenner, Pitman, Irving and Greenwood... and while they don't disagree with each other completely.... there are some differences. :roll:

But - we'll get to that.

Back in the workshop I double checked the current setup:

This note tells me how the timing pinion on the crank-shaft was fitted prior to dismantling:


And that's how I fitted it:


The books had said that one trick was to fit the mag-platform/timing chest cover to check the backlash and to ensure that the gears weren't jumping about.

So I fitted the studs: using the double-nut trick to get the studs themselves nice and tight:


Timing chest cover in place (but not pushed fully home)
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This is what I was getting as backlash with both valves open.




2 degrees of backlash.  1 degree is what is mentioned in the books, so that's something to talk to the guru about... along with other things, but I'm not distubing him on Easter weekend!



I carried on regardless - it's all good practise.
You can't really see it here.... but the push rods are ever so slightly not straight.... which means they should be replaced.



I played with the timing wheel and piston tell-tale until I got the 0 degree mark right at TDC. 


The tappet clearance, according to one of the books should be 0.003" and 0.004", then reset to 0.002" once the timing is done: which seems a tad odd... but this comes from the Greenwood book - which is based, from my understanding, on racing experience.






Set both sides easily enough.

This is the timing numbers from the 4 books I've got....


I wanted to check the valve openings with the dial guages, so I dug out the ally bracketing I had found a few months ago and made a start on making up the 2 small brackets I needed.








Bit of heat to make the bend easier


Along with an assist from my number one, all time, favourite tool.


The holes for the small end are 1/4", and I ended up doing the other end 1/4" as well - turns out the dial guage lugs were exactly that size.


Guages fitted and aligned.



I lost count of how many times I spun this thing.
I marked the "correct" timings on the wheel in black, and the timings that I had, which were surprisingly close for a first go, in red. But I can't quite make sense of the offsets: I had expected that if they were "early" at one point, they'd be early all round.... but they're not... not quite... I am wondering if I've got a "sporty" cam here... but will be talking to the guru about it first.



One other thing I have seen a photo of, is a little handle on the timing wheel to make it easier to rotate, so I figured that might be worth adding.


I used an M5 bolt and a cork...    It may get improve upon in the future!


So - I need to talk to the guru next week, and buy new push-rods, along with the ends (which come separate), a new oil-union for the rocker box, some new oil-nut fittings, a spanner to fit the buggers (if I can find the right one),

I have another job coming in which necessitated moving a few things about in the workshop... and while doing so I discovered that the right side fork is weeping oil... and there was oil under the gearbox, which I think "might" have been coming from the kickstart shaft.  Goldarn it! GAH!

If you ever have to (God forbid) centre the conrod in this way again, stick a piece of masking tape on the face of the rod and measure and mark the centre line using vernier calipers.

I was trying to do exactly that with the rule laid against the conrod sides but it was quite difficult to find a point on the cases that the caliper point would hook into reliably and consistently. Which is why I ended up simply using my Mk. 0.9 eyeball.

But making a centerline on the conrod to facilitate that would be an excellent idea, thank you.

So - yesterday I got the opportunity to dive into the workshop...

4 hours of facking about later....

In imperial...


and metric units:


9.3 kilos.... yeah - that's pretty hefty.

I pushed some oil through the big end to clear it out before proceeding:



Then left it to drain for a few minutes


Before starting the iterative process of finding the best mix of shims for an acceptable end-float and conrod centering:

Each trio of photos will be: the measured overall end-float, then conrod vs case centre-line with crank to LEFT, then crank to RIGHT.
one:




two:




three:




four:




six, no five! :

(fecking guage)




That's acceptable and seemed to be as close as I was going to get with the shims I have.  Between 0.015 and 0.020 overall end float, and the conrod (allowing for the big-end float as well) is as centred as I can get it.

A sure sign of a troubled mind.....


I've ended up with a very thin shim on one side, and quite a thick combo on the other.

I believe the main reason for this is that the main bearing liners are of different vintages, and protrude into the cases by different amounts (which is the main reason for the adjustable shimming).  The old liner in the Timing side case is only slightly proud of the case it fits into (which is the side of the crank-wheel I had to grind down).  The new liner I fitted into the output side is much more proud of the case: ie, it has a thicker "brim" (think of it shaped like a top hat); so, to center the conrod, there is less "room" on the output side between the liner and the wheel.

I think I spent about 3 hours on that: each measurement above represents unbolting the cases, pulling out the wheels, pondering the next combo, then reassembling (making sure not to fling bearing pins everywhere), bolting up and resetting the guage.  The guage was a bugger to zero each time.

I then restarted the assembly process:
First get the mating faces clean:

Can you get high on meths fumes??


Stick the wheels in with the bearings and shims, then fetch the sealant.


Oh FFS!


Even with having squooged the stuff up and down the tube to try to get it mixed a bit better.. (metal tube - hence the leak above) it still came out very runny. In fact, it literally poured out of the tube (which is why I ended up with slightly more on there than I had planned.  )




I cleaned it all up as best I could before it got too sticky




It does make quite a mess....


I can only hope that there isn't too much dribble inside the cases themselves.

Just for shits and giggles I checked the end-float again:

(fecking guage)


Satisfied with that, the end-float is still as I hoped and with luck, the 3Bond will go off properly.

I decided to carry on and fitted the piston again: naturally I scratched hell out of the piston getting the sodding gudgeon pin circlips in:




Then fitted the barrel rods:



To get a good "heft" on the barrel rod nuts I put the whole thing into the vice briefly:


So - we're back on track, if behind schedule slightly...


I left it there for the evening to let the 3Bond go off, and to ponder the next move:
Specifically: do I try the 3Bond on the base gasket again... or use something else: the immediately available options are Hylomar Blue, or silicon RTV.  I'm tempted to try the RTV to be frank, mainly because (from memory of last time I used it), it's much, much less runny than the 3Bond, and so easier to be exacting about where it's applied.  I don't really want too much of it dribbling into the cases.

So, I went back in and fed the cat:

More grinding...



(forgot to block off the timing shaft oil feed... oops )

Progress:


Checking with a 1/2" wide rule


Checking with a 1" wide rule


The cleared area needs to be around 4/5" from the shaft - approximately.

Almost done....



After all that I stuffed the wheels back into the timing side case... and it's STILL "just" touching that odd ovoid shape in the cases with no shim in place - and it's just the outer parts of the ground area (there's a distinct double touch I can feel).

However - there WILL be a shim in there and when there's a shim, there's no touching. So that's gone relatively well I think.

I buttoned up the cases dry again and without any shims to check the end float, and conrod centrality, with the intention of fitting shims not just for good end-float, but also to get the conrod as central as possible.

Overall end float with no shims :


Using the case joining line as the "centre-line" for adjusting the conrod centering. There's nothing else on the cases that is machined in any way so that it could be used for an accurate measurement for centre-ing the conrod: ie, there's no matching face or point on either side that I can use to measure the offset to the conrod and get a balanced measurement with any accurary.
This is with the wheels as far "left" as they will go:


This is with the wheels as far "right" as they will go (the rule hasn't moved).


So - need to play with this a bit more, figure out the shims and tinker, then rebuild again.

Over night I also had a nasty though that I may have put the output side case on without the main bearing pins and carrier... D'OH!  So I'll be checking that end-float again!

I think I'm getting a little pressured and starting to make stupid mistakes - so need to try to slow down a bit and be thorough.