SQ4 Primary drive

[xavier.devars]

Dear Arielists,

I found the SQ4 primary drive to be quite a leaky one, especially with its two parts inner chaincase. Would that be sacrilege to run it with a spray of rear chain lubricant from time to time, thus avoiding the unwanted left rear end lubrification ? Or is there an effective way to seal this case ?

Regards,

Xavier

[will_curry]

The chaincase oil not only lubricates the chain it also lubricates the engine shaft shock absorber
and the clutch free-wheel bearing. Spraying the chain won't do that.

Before going too far it's worth checking that the flanges on both the inner and outer chaincases
where the mainshaft goes through are in good order, If they are damaged as soon as you start
the engine oil will leak out.

When I've had to disturb the inner chaincase on my Mk1 I fit it back with the 4 bolts a little slack
so it can move relative to the crankcase and then fit the outer chaincase without sealant or gasket.
I then titghten up the two outside bolts, take the outer off again and tighten up the two inner bolts.
Finally I refit the outer chaincase with a decent gasket and sealant.

[markus.nikot]

Not to forget, the coolingfactor for the chain.
It heats much more up compared to the rear chain caused by its realtively hight tension.

Markus

[xavier.devars]

Yes, forgot the shock absorber. Anyway the pinions cover decided to leak also. Guess I need to have another try at sealing these.

Thanks,

[xavier.devars]

Hi guys,

Okay, now I think the primary is well sealed. Most of the leaks must have come from the damaged screw bosses inside, so I put some O-ring under the screw heads of the leaky ones. We’ll see.

What I am concerned about, now, is that the clutch basket has some radial movement (everything tight, no play between basket, clutch hub and shaft), has if the clutch wheel center was excentric, thus tightening and slacking primary chain. I have changed the needles and their brass holder to no avail, the shaft is brand new and so is the sleeve.
Any ideas ? Are clutch wheel centers available ? Can it be the culprit ?

Regards

Xavier

[will_curry]

How are you checking this? Are you turning the whole engine over on the kickstart
or do you have the clutch and the engine shaft shock absorber dismantled with the
primary chaincase off?

In my experience there's usually a little bit of variation but I'm not sure how to
describe it objectively.

[xavier.devars]

Well, the primary is complete and tight, except for the clutch plates, and I turn the wheel by hand.
So the shaft and its sleeve turn inside the clutch wheel.

[will_curry]

Is the variation in the tension of the primary chain too much to run the engine safely?

The clutch basket, especially when the six holes that the mounting bolts go through are
worn, is often markedly eccentric but this won't affect the primary chain.

[xavier.devars]

Well, I think the clutch basket movement is due to the clutch center moving eccentrically.

[xavier.devars]

Chain tension variation can’t be good, especially considering this is only a simplex. Could the clutch wheel (refab) be the problem ?