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.