7 replies to this topic

[alpder]

Trying to trace the cause of oil on my clutch.

 

Engine is an A+. Gearbox and tx-case are pre-A+ direct/remote. Clutch is Verto. Primary gear is MiniSpares C-22G1053 . The entire unit was rebuilt (but by me) 600 miles ago. The clutch oil seal looks fine and there's no indication of oil on the back of the transfer case to suggest a leak there. But there is oil on the splines and on the friction surfaces.

 

Crankcase has two breathers which are tee'd together and connected to the carb - so (hopefully) crankcase pressure isn't the problem.

 

I can feel plenty of sideways slop (not end-float) in the primary gear on the crankshaft. My cheapie dial-gauge (which I don't fully trust) measures 0.12mm (5 thou) of radial movement. Seems to me that's a big old gap - and it certainly *feels* a lot - but MS's documentation suggests it's not wildly excessive. So what stops the oil seeping down that 5 thou gap and out into the clutch?

Edited by alpder, 04 April 2024 - 04:56 PM.

[Spider]

I believe these run additional clearance in a vein attempt to avoid them eating your crank tail. The original gears that had the Deva rear bush ran 0.0030 to 0.0045" axial clearance ( with 0.0035 to 0.0065" end float).

The issue with running a bigger clearance from the bush to the crank is that if you have high crankcase pressures, it will push oil through here, I guess that may help it from not eating the crank. The other issue is that in time, it will cause the cntre of the clutch plate to crack out, but you usually need more clearance for that to occur,

[alpder]

I believe these run additional clearance in a vein attempt to avoid them eating your crank tail. The original gears that had the Deva rear bush ran 0.0030 to 0.0045" axial clearance ( with 0.0035 to 0.0065" end float).

The issue with running a bigger clearance from the bush to the crank is that if you have high crankcase pressures, it will push oil through here, I guess that may help it from not eating the crank. The other issue is that in time, it will cause the cntre of the clutch plate to crack out, but you usually need more clearance for that to occur,

Thanks Spider. MS say the clearance on their gear is 3 thou (+2 / -0). So my 5 is just within tolerance. I believe I have reasonable crankcase breathers. And the engine is a new rebore with new valve guides/seals. So crankcase pressure shouldn't be an issue. So... baffled how oil is getting onto my clutch.

[imack]

I don't know the answer, but I keep getting the same issue. At 5 thou axial clearance I get oil getting between the crank (new MED/Arrow) and the primary gear bush ( new minispares s/c evo). 3 x breathers open to atmosphere. The floating bush tolerances seem to vary a little, if I can get the clearance down to 4.5 thou by selecting different floating bushes I seem to eliminate the leak.

Attached Files

•  Screenshot_20240404_182037_Gallery.jpg   57.22K   1 downloads

Edited by imack, 04 April 2024 - 05:22 PM.

[alpder]

I don't know the answer, but I keep getting the same issue. At 5 thou axial clearance I get oil getting between the crank (new MED/Arrow) and the primary gear bush ( new minispares s/c evo). 3 x breathers open to atmosphere. The floating bush tolerances seem to vary a little, if I can get the clearance down to 4.5 thou by selecting different floating bushes I seem to eliminate the leak.

Certainly wouldn't mind a smaller pair of bushes. You'd think there would be undersize options to buy.

[ACDodd]

Erm undersized bushes are no problem, however measure the crankcase pressure at 6000rpm, and see how much blow y you have.

Ac

Edited by ACDodd, 04 April 2024 - 05:36 PM.

[alpder]

Erm undersized bushes are no problem, however measure the crankcase pressure at 6000rpm, and see how much blow y you have.

Ac

Thanks AC... I just PM'd you before I saw this post - I figured if anyone had the bushes you would. The engine's out so can't measure. And while it's out I might as well fit the tightest possible bushes before I rebuild and reinstall - mine are at least on the limit and can only get worse. What are the chances of bringing the crank to you for some machined-to-fit bushes? Or, more realistically, what's the best way forward?

Edited by alpder, 04 April 2024 - 05:49 PM.

[ACDodd]

Pm sent.

Ac