Clutch basket rubbing on primary cover

[phsammut]

I removed the clutch cover from the primary of my 1958 Square Four to see why I had some clutch slip. I found a lot of powdery grey stuff in the cover and coating the outer primary cover. The plates were fine and dry but, on removal of the basket, it was obvious that the back of the basket had been rubbing on the outer portion of the alloy cover and it was fine metal (aluminium) powder that I’d seen.

I read the comment on Draganfly”s website in which they mentioned this problem and it suggested I might have too short a mainshaft. However, if I grab the chainwheel I can slide it in and out (towards and away from the gearbox) by about 1/8” suggesting it is more than long enough. When pulled away from the ‘box, it appears to line up with the crankshaft sprocket better and the basket no longer rubs (if I temporarily replace the outer primary cover). I do not see that there should be a spacer or shims behind the chainwheel in the parts book - should there be? Any foreseeable problems if I do fit a spacer?

Thanks in advance.

[Simon.Gardiner]

Are you missing 3394-36 and 3397-36 (the spacers that go behind and in front of the chainwheel, and probably take up about 1/8" between them)?
https://draganfly.co.uk/product-categor ... 6-58-type/

SG

[JohnnyBeckett]

hi i have had the bolts that hold the clutch basket to the chain wheel i first thought i had the Wrong spacer but it turnout to be the new bolts i got off the club spares where a bit to long they was sticking out of the chain wheel and rubbing on the casing

[phsammut]

Thank you, Simon. I was inaccurate when I stated I do not see a spacer - I am aware of the thrust washer, 3394-36, and believe I have one (I've not removed the chainwheel yet) but seem to remember it is similar to, or identical with, 3397-36 and is very thin - mine measures only 0.020" thick. Since one is outboard of the chainwheel, it wouldn't help displace the chainwheel outward and therefore would need, I think, a spacer roughly 0.125" thick. Does that make sense?

Interesting thought, Johnny, but I see quite uniform rubbing marks on both the primary cover and the back of the basket, rather than grooves but I will certainly re-check that.

[Simon.Gardiner]

Mine are much thicker than 0.020 - more like 0.060 (just measured one to check).
The chainwheel only needs to spin freely and to be in line with the engine sprocket - if your particular set of components can (or need to!) accommodate a spacer behind the chainwheel to improve its position I'd say do it!

(If you only need to move the basket out a little use one - or maybe two - of the locking ring washers for the clutch basket bolts under the basket (ie between the basket and the chainwheel) as a spacer. I had to do this with the FH engine in the bike, there's no issue at all when it's running as a VH. The ruling factor here is the heads of the clutch basket bolts having a clearance to the clutch centre. )

SG

[paul.jameson]

My Healey which is basically 1958 Mk II configuration needs one of the locking ring washers under the clutch basket or else it catches just like yours.

[will_curry]

1/8" does seem rather a lot of endfloat on a mainshaft. It's controlled by the length of the
sleeve on which the kickstart ratchet lives. I'd check that the nut that holds it all together
isn't coming slack. Be careful tightening it as it is easy to total the threads on the mainshaft.

It's also worth checking that the chaincase is not being pushed out of position by the fixing
beneath the clutch dome.

There's been some other posts on the topic elsewhere on this forum.

[phsammut]

Thank you, Simon and Paul. I had tried moving my locking ring washer to behind the basket - it improved the situation but did not cure it. I will have to order another couple (and, probably, longer bolts). I tried a spacer behind the chainwheel, which looked good but, not surprisingly, it bound the clutch centre once I tightened the nut, so that is no answer.
Thank you, Will, also. The centre nut was a still very tight at disassembly. I believe I have the appropriate spacer for the fastener under the dome, but will reassess as you make a good point. I will check the archives for similar threads
Kind regards,
Paul.

[simon.holyfield]

Mine are much thicker than 0.020 - more like 0.060 (just measured one to check).
The chainwheel only needs to spin freely and to be in line with the engine sprocket - if your particular set of components can (or need to!) accommodate a spacer behind the chainwheel to improve its position I'd say do it!

Mine are around 0.060" too...

These obviously have to be the right thickness in order to take up the space without binding. I'd contact Gearbox Spares and see if Geoff has a new set.

[Brian_Walker]

One other thought my VCH had a similar issue, turned out that i fitted a gasket to the inner case of the gearbox that was thicker than the original paper gasket. This in turn was moving the mainshaft ourwards on the kickstarted side hence chainwheel closer to the iner cover. I know the cover on the SQ4 is a 2 piece affair but if any work has been performed on the gearbox it could still cause a 0.040-0.060" offset.
Brian