Clutch dragging

[Pompeydave]

Hi all, got some routine maintenance to do on my 1970 Turquoise GP125 before the annual 'Proud to be a Pompey Scooterist' trip to the Normandy D-Day beaches in June. Ever since I've had the bike (nine years now) it's suffered from clutch drag once hot. Not enough to be a real pain, but I'm fed up with it now and need to fix it.

Previously, I've replaced the old standard steels with thinner flavour versions to make sure I'm well under 14mm. It made no difference. I then ditched the Surflex cork plates to replace them with ReadSpeed thinner plates that are synthetic and don't expand. That made no difference either. I've tried fitting a new cable, moving the arm to different positions on the cam, different strength springs, none of it makes any difference.

I'm now starting to wonder if the sprocket and spider assembly is at fault. I'm sure I read somewhere that the spider needs to sit 0.1mm above the level of the sprocket when viewed from the back otherwise clutch drag will be an issue. Is this correct and if so what can I do about it?

[Storkfoot]

Yes it is important although I am unsure if drag results from not having such clearance. MB do shims to assist in resolving.

[Norrie Bodge]

Yes it is important although I am unsure if drag results from not having such clearance. MB do shims to assist in resolving.

https://www.ebay.co.uk/itm/195516587274 ... media=COPY

[Adam_Winstone]

Lever travel?

Spring type (going coil-bound)?

Centre spring?

[Pompeydave]

Lever travel is correct and the lever is a standard fit and it’s in good condition. I’ve tried several different spring sets to no avail and there’s no centre spring fitted.

[Knowledge]

To me, clutch drag usually means that some of the surfaces are still rubbing together when the clutch lever is pulled in.

Are you certain that there is enough space in the clutch basket for all the plates plus a millimetre or two to allow them to separate when the lever is operated?

I have modified many an outer basket so the ears of the cork plates can sit a bit lower, giving more clearance to allow all the plates to separate. See photo top left on page 125 of Sticky’s green manual.

[Pompeydave]

Definitely. Nothing stopping the plates separating either. Correct level of oil in the crankcase also. Doesn't make sense.

[duncan1958]

Have you tried a different oil ?
Just a random guess as you seem to have tried most things.

[Knowledge]

Just on the oil question, I use SAE40 with no detrimental effect

[alex_hughes]

One of my bikes has always suffered clutch drag when its been on a bit of a run. I think it may be a misalignment somewhere because I've done everything you have plus shorter lever etc etc. The only thing I have not done is check the alignment and re-shim. I plan to do this - but at the moment I am time-poor.

Over the weekend I changed the oil from standard gearbox oil to ATF (Automatic Transmission Fluid), as per the suggestions of WT1 on this forum.

Yesterday our club went on a run of about 100 miles, lots of clutch work because we were travelling through villages and small towns.

No drag. Or slip.

It worked for me.

Only done 100 miles so don't know if there will be a downside yet, but WT1 says no downside to this change.

I used ATF semi synthetic from Halfords. Dexron 3. Just emptied out the old and poured in the new, made no other changes.


PS I realise that this does not solve any underlying fault in the mechanism, but it may be worth trying it ahead of further investigation.

[Pompeydave]

Yes could well be worth trying, thanks for the tip.

[jonoy]

Maybe try Putoline light gear oil

[Tacolneston Nik]

I had a similar problem and it was the standard Series III crown wheel which was causing the issue. With the side casing off everything worked fine but with the side casing on the problem re-appeared. It was pointed out to me that in Sticky's manual when kitting an engine do not use the standard crown wheel. As soon as it was changed everything was fine and has been ever since...

[Pompeydave]

What did you replace it with to fix the issue?