sprag clutch

A

andre

Senior member
Piet - in a recent post you mentioned that you balanced your starter clutch. Are they inclined to be out of balance?
I had been thinking that at 22years old my SFC1000 starter clutch might be due for a clean and reburbish. Apart from a balance, I presume I should replave the springs. Should I replace the plungers and rollers also? Do the plungers need oil or a little grease on them? Happy to receive advice.

Thanks
Andre
 
Andre,

Just a point to be remembered when balancing the rest of the crank assembly.  The clutches of the 750s can be out by up to 10gr, not much, but while you're at it, might as well..... :D  The Mk I triple clutches are quite a bit smaller, couldn't detect much in mine so I left it as it is.  Might be worthwhile on the Mk IIs though, quite a big lump with the alternator rotor et al.

By all means, replace the springs, if just for peace of mind.  A real pita having to pull it down once more in 2 weeks time when the clutch starts slipping.  The plungers rarely need replacing if the clutch works OK, same for the rollers.  It's the ones that are left unattended for years that tend to self-destruct!  Do check the condition of the cylindrical part of the freewheel where the rollers bear upon, should be reasonably smooth with no large dents and bumps or pitting.

piet
 
Balance the sprag clutch? is this real?
its only supposed to turn when the starter is operating,
come on Piet we know each other better than that surely, or maybe it is a late April the first.
CLEM
 
bearing in mind the relative low weight (of the bit that turns when the motor is running) and added frictonal loses,(bearings,gear teeth, oil drag) is it worth balancing?, realy? come on, be honest !
CLEM
 
Clem,

What's the use going to all sorts of measures to get the crank balanced spot on and then stick a component on its' end that's out by 10gr??  No point in it at all!  Either do it all or leave it as it is.

Bear in mind, each single gr. of imbalance rotating at the cranks' circumference multiplies itself to something like 8kg at 8000rpm!  As I stated, the Mk I triple sprag clutch is relative small and quite symetrical, not much to be expected.  The 750 clutches are out by as much as 10-12gr, haven't checked the MK II triples yet but I expect to find at least as much imbalance as the 750s due to the sheer size and weight of the clutch/alternator assembly.

Not only rider comfort is enhanced by a properly balanced crank assembly, bearing loadings are reduced and thus long-term reliabilty increased, too!

piet
 
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