Series 1 sprag clutch repair

A

andre

Senior member
Gents
Sprag clutch has been 'slipping' sometimes instead of turning engine. Just want some advice on the repair process.

When motor had last major work I stripped sprag, replaced springs, cleaned, reassembled. I dont recall replacing rollers, so I should do this time huh. I can buy them singly from a bearing shop, or must they be ordered from a Laverda parts supplier? I'll check plungers again, but would expect they're ok?
I cant see anything else wrong with the sprag. Surface that the rollers engage on looks reasonable, and I'll get a local second opinion.
I see the bearing each side of the sprag doesnt appear as snug on the crankshaft as I'd expect, and the outer one not as tight in the alloy cover as might be expected. Looks like I'd put some bearing installation loctite on the outside of the outer sprag bearing to try to locate it better in the case. Any advice on how 'secure' these bearings should be. They seem in reasonable condition, but I'm inclined to replace them as a matter of course.

And - with the IIS ignition wires not all that easy to disconnect from the white fitting at the pickup end, so I'm inclined to leave them in place, fitting a new gasket by putting a cut through the outer part (dry) where the wires go through. Should I put gasket compound both sides? Doesnt look like I did last time it was off.

Any advice appreciated.
Thanks
Andre
 
I've found one plunger is stuck in the fully compressed position. Just gotta get it out somehow...?
 
Andre,

The rollers only need to be replaced if they are damaged or worn.  Measure diameter and inspect for flat spots.  If all is OK, they can be re-used.  As replacements only cost pennies, greater peace of mind is attained by replacing the suckers :D.

Always replace the springs, they are usually the culprit causing slippage, although the MkI clutch seems to hold up better than all others.

Check the driving ring surface for dents and damage, only once this is worn beyond a certain limit will it cause slippage.  Place a pair of rollers in their place opposite each other in the insert, half-way along their respective ramps.  Measure the distance between them, should be within a few 10ths/mm of the drive spigot diameter.  If you find the diameters match when the rollers are palced at the end of the ramps, ie, fully engaged/smallest distance, the drive spigot is worn and will be the cause of the slipping.

Inspect the insert that locates the rollers for cracks, these allow the insert to expand and thus reduce pressure on the rollers while engaging, causing the clutch to slip.  Also inspect the edge of the bore of the plungers, these are often quite sharp and wear the springs prematurely.  The edges can be chamfered with a small grindstone in a Dremel.

The large diameter bearing fitted in the alternator housing is prone to wear and roughness, often needs replacing.  Should be an interference fit in the casing but are often loose.  Re-fit with a drop of Loctite.

Also make sure the entire clutch assembly is firmly tightened when the sleeve nut is done up.  This nut very often loosens and then wears at the contact surface to the clutch housing.  Signs of wear can be machined flat and the missing material compensated with a shim washer placed between clutch housing and sleeve nut.

Jammed plungers can be removed by slamming the assembly down on a wooden surface.  If it doesn't budge, try fishing it out with a magnet or hooked instrument.  If all else fails, you're up shit creek... the tin cover needs to be removed, the insert removed from the housing, the rearward plug in the plunger bor bore removed and then the plunger itself.  A bugger to re-assemble.  Use new rivets, M5 screws usually are not up to the job of keeping the thing together over a lengthy period.

HTH,
piet
 
piet said:
If all else fails, you're up shit creek...
Click to expand...

You're obviously not a serious bodger Piet.
Sticking a welding rod to things that need to be pulled out of holes is always a possibility. I did that today on a bolt that was snapped off and managed to unscrew the broken stub.
Where there's a will there's a way  :D

Cheers,
Cam
 
+1 with cam for the welding rod,
then snip it to about 150mm long and use it to wiggle the plunger out of its bore.

I have had to derivet and split one sprag clutch, it was not an easy job, and lots (I do mean lots) of heat was needed to get the shrunk in cast iron parts for seperatiog, but the plungers in that one did not come out even with bits of welding rod welded to them, and much oxy acetylene heat, I have seen holes drilled in the clutch (at a tanget) and then use thin probes to drift them out, but It needs to be apart to drill those holes from the inside.

CLEM
 
Guess it all depends on how deep the plunger is jammed in the bore.

I am not such a proficient welder to attempt such a bodge, a lot easier and quicker for me to disassemble the clutch and do it the "hard" way! :D

Anyway, once completely disassembled, the clutch inner ring can be far better examined, you often find cracks not visible from the outside of the assembly. :o


Clem,
The inner ring is definitely NOT cast iron, that wouldn't last 2 start-ups before crumbling.

piet
 
got the offending plunger out. The spring was in pieces. The plunger ID (where the spring fits) is 4.5mm. I think its been bored out for over dia springs. Is 4.5mm ok for stock springs (4mm OD). Some of the plunger ends that contact the rollers look a little 'hammered'. I guess I could hand grind them smoother. Or at this point, new plungers?
Is Wolfgang back at work?

Thanks
 
Andre,

The spring needs a bit of room to move around, don't think the suckers can be bored as they are hardened right through.  Either smooth them off or get new ones.  In either case, check the edges for burrs that might eat the new springs quickly.

piet
 
Clem,

I rather have the impression the part wss stamped from plate and then machined and hardened.  Ramp surfaces are usually quite rough and one edge always seems to be rounder than the other.

Ends up being quite brittle, hence the tendency for cracking

piet
 
Replaced springs, rollers, plungers (thanks Red), bearings, and hey presto works perfectly. What was I worried about? Overall, very easy and cheap to fix.
 
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