TS Supa five 3rd gear issues

[veedub1955]

Hi i have an issue with 3rd gear, when engaged its as if the clutch is slipping and then it bites fine then slips in and out randomly. It only happens in third. I fully rebuilt the engine last year and clutch and plates are new and has perfect adjustment and bite. I dont know if i imagined it but it seemed to happen after catching a false neutral? After changing the gearbox oil today thinking of trying simple things first I have now come to the conclusion that its not positively engaging 3rd gear. Has anyone else experienced this before i split the case and delve further. Its performed faultlessly until now.

[mr_luke]

Your symptoms sound identical to the problem I had with my ETZ 250, and I believe it's a fairly common problem. The underlying cause is supposed to be slightly miscut dogs on the 1st/3rd sliding gear and the 3rd gear pinion. These dogs are engaged when 3rd is selected, and they're supposed to be very slightly angled, so they tend to 'pull in' together under load. If they don't have this undercut, either because it was never there or due to wear, you're relying on pressure from the 1st/3rd gear selector fork to keep it in gear. When you split the cases I think you'll find the selector fork is badly worn, and possibly nicely blued; the dogs on both the gears mentioned will be rounded off and smooth. Replace those three parts, and you should find it works perfectly again.

[arry_b]

From your symptoms, I'd suggest it's unlikely to be a gearbox problem. A duff box won't feel like a slipping clutch, and the Supafive boxes suffer far less than the ETZs with the miscut dogs problem.

I has something similar on my 301 earlier this year. Third is where you'll get maximum torque when you're pressing on a bit. So perhaps you have either a worn clutch, or (more likely) your clutch isn't tight on the taper. Although it doesn't require a crankcase split, you should take the clutch off to make sure the taper on the crank or clutch centre isn't scored.

Mine had scored the clutch centre very badly, but the crank was untouched.I fitted a good used centre from a spare clutch and normal service returned.

You may be lucky and there may be no damage, so you should be able to torque the clutch nut up properly and replace no parts. You *should* dismantle to make sure, though.

[veedub1955]

Cheers for the replies

Checked the clutch and all ok it only does in third gear only and riding it after the oil change has highlighted better that it dosent feel like its going into 3rd properly, all the other gears click in nicely. Not afraid to split the case so ill delve deaper!!

Thanks for the advice