Am needing some help/advice. Have bought a 1961 T20 and recently topped up the primary chain case with oil, on the next run found it had leaked out onto the drive sprocket. I'd put in red ATF, so the leak was definitely from the primary chain case. I've not had a T20 engine apart, but I know that on the Triumph 500 and 650's there is an oil seal set into the back plate behind the clutch assembly. I can see that this engine doesn't have a removeable back plate, can someone point me in the right direction, is there an oil seal on the inboard side of the primary chain case and is it accessible once the clutch has been removed, the Haynes manual is pretty vague. Thanks.

 

 

 

 

Yes there is an oil seal behind the clutch Fits in the case an slips over the sleeve gear bush 

Thanks for that, I was sure there would be a seal, just not sure where they'd hidden it!

One quick question, I have used ATF in the primary chain case on the bigger Triumph engines with good success, little chain wear and  clutch not slipping and easy to identify should it escape.

Have you used it on a Tiger Cub and if so have you stayed with it?

Thanks Elliot

 

 

Check behind the clutch.  Most trials Cubs have been modified to fit a final drive sprocket access plate (similar to T100 twins).  This lets you change the final drive sprocket without having to split the crank cases!  

If it has been modified, the thin plate should have an oil seal fitted (with the spring side of the seal facing the clutch).

ATF is fine for the clutch.  You only need enough to cover the primary drive chain so I put 100ml in instead of 200ml as stated in the manual.

If the clutch slips when kick starting you can fit stronger springs and add an additional plate with billet ally pressure plate if required which available from a number of Trials Cub Specialists.

Thanks, that is good news. The bike has a 13 tooth final drive sprocket already fitted, so hopefully the mod you mention has already been done. Any ideas who supplies that oil seal for the access plate - or is it a standard Triumph T20 part?

I've usually reduced the drive chain case volume of ATF - but thanks for the good advice.