Troubleshooting a JAP Special

[Rockburner]

Not much to report today.

Refitted the timing chain cover and the pumps, after cleaning out the oil feed tube with some very handy little brushes I have.


Currently waiting for this nut to turn up.


And refitted the primary chain cover



Obviously all that took me about 2 hours of faffing about and dithering, as per usual

I reckon that, in a pinch, I now probably could strip and rebuild the engine over night.... if I had to.... but it's not something I'm going to try.

Fingers crossed that nut will turn up tomorrow and I can get out for a spin and see how it's behaving after the clutch rebuild.  I'm fully aware that it's down on power and compression, but I want to actually ride the thing a bit more before stripping it down again, hey - it'll keep me busy over winter again.

[Rockburner]

I took it out for a spin this evening, and it's running fine, apart from the fact that the damned clutch is slipping at anything over 50mph.

I suspect it's just not setup correctly so will have a play this evening and fingers crossed it'll be good for the weekend.

In good news, it's nigh on oil tight now, apart from that one cover i haven't tried to seal, the timing chain cover.

Incidentally, if anyone is at a loose end and is near the South Coast on Saturday, there's a classic vehicles meet in Selsey, just a suggestion.

.... Later...

So, I think the clutch was indeed badly setup - there was zero play in the lever in the gearbox when I looked this evening.  So I've pulled it apart again, because I was kinda pondering if the plates were badly worn...

however... according to the details I've found: the friction plates should be 0.138" thick, the plain plates 0.080" and the single-sider on the outside (which the pressure plate pushes against) should be 0.110".

I measured them all:


The plates I have are :
Plain plates: 0.080", 0.082", 0.080", 0.082", so they're fine.
The single-sider is 0.111", so it's fine
and the Friction plates are : 0.171", 0.158", 0.172", 0.170"  So, err they're all too thick.


Which makes no sense. (to me at least).  By all rights the thing should be dragging like crazy, not slipping!  :wtf:

I also checked them for flatness on the flatest thing I've got


One or two had a "little" bit of rocking movement. I'll look into how much new plates are and think about it.

SO I did the only thing I can do for tonight....
I buttoned it all up again, and reset it again, trying to follow the manual's instructions as best I could


I think clutch setup is a bit of a black art to be honest....

Oh, and it looks like I was being a bit presumptious about the oil tightness....
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Hey ho, it's better than it was!

[chaterlea25]

Hi,
Looking at the photos of the clutch centre hub it can be seen that the splines have been ground away, this is why the clutch is getting so close to the final drive chain!
It may have been a bodge to get the primary chain lined up to the engine ??

John

[Rockburner]

Hi,
Looking at the photos of the clutch centre hub it can be seen that the splines have been ground away, this is why the clutch is getting so close to the final drive chain!
It may have been a bodge to get the primary chain lined up to the engine ??

John

That's possible, the primary chain run is very much to the outer limit of the front sprocket carrier. 

That doesn't explain the washer that was there, pushing the clutch out futher though! 

It could be that the ground away material was either from another fitment on another bike, or it was an experiment that didn't work out.

I have a feeling that the washer was there so that the clutch could "float" on the shaft a little - the clutch hub nut was NOT very tight when I undid it. 

When I tried to do it up tight, with the washer in place, the washer was pushed hard against the outer main shaft of the gearbox, locking the 2 gearbox shafts together.

I've done the clutch up tight on it's shaft, and while the drive chain is very close to the back of the clutch, there IS clearance.  I'm going to be scouring the autojumbles for another clutch I think, or parts thereof.

[Rockburner]

Slacked off work this afternoon to take the bike out for another quick spin.

and there was a lot of spinning.... the damned clutch is STILL slipping.  It's obvious in all gears, in first it won't "bite" above a certain engine rev-speed, and in the other gears it simply won't go above 50mph.

So I dragged it's sorry ass back to the shed and had another look.

I screwed the springs in a couple more turns, and made sure they seemed to be "balanced" : ie the pressure plate lifts equally all the way around (as best I could)


I confirmed that there was enough slack in the push-rod linkage, there's plenty.


And then buttoned it back up.  I'm taking it down to Selsey tomorrow whatever (well - unless it pisses it down...), and then we'll see after that.  I think I now know roughly what the clutch "is" (ie which type, and what plates I would need to buy), but there's still a few details I can't tie down, so more research to do. 
I'll look into new plates and new springs, they're the only things that should need replacing.

In the meantime.. the next little project is going to be stripping down the Pilgrim Pump to replace the gaskets: I'm pretty sure that the gasket under this cover plate has gone - there's a definite "snail-trail" coming from it.




"These things are sent to try us..."

[Rex]

It might be grandma's eggs, but have you tried cleaning the friction plates in a solvent like celly thinners?

[cardan]

And/or boiling them in a water + strong detergent?

[Rockburner]

What I actually did, was to put them through a ultrasonic session, then a good brass brushing.

After taking to a subject matter expert today at the local show, I think the washer that I mentioned is supposed to be in there to get the gaps right, so I'm going to strip the clutch down again, probably soak the plates in petrol for a bit, then reassemble with the washer. Apparently it's supposed to sit on the OUTER shaft, ie the gearbox output shaft, but I think I had it on the inner shaft which is why it was binding up the gearbox when the clutch centre nut was done up tight.

I'm going to need to reduce the outer diameter of the washer though, so it doesn't foul the clutch stud nuts on the back of the clutch.