Clutch slip & gearbox probs again!

[dobbslc]

Ok the clutch is still slipping on the 3TJ RRSP track bike, I went to Mallory yesterday and it started slipping at about 12000 rpm.
It' a completely rebuilt & tuned engine 65-70 bhp and the springs & plates are within spec it also has a banded clutch basket to stop the "fingers" from spreading, any ideas? I've seen two lenghts of springs in the manual 41 & 37mm what are the right one's for a 91 3tj sp? I've got the short one's

Next is the gearbox it somtimes slips out of second back into first gear (mostly around Devils Elbow which is not fun!) although once it's in gear it stays put. It all looked ok before I put it back together but are there any common faults that can be cured without stripping the engine again?
Thanks in advance for any help chaps.

[Taggyd]

ooo not nice! sounds likes it doing it as you nail the trottle out of the bus stop? and isnt engaging properly the first time, have you moved the lever on the spindle? it might be an idead to bring it a bit lower as you're probably leant over as you try and change? are you going through the bus stop in first?

[dobbslc]

The lever is set ok, I have big feet so was checking for this! I'm short shifting to second before the bus stop as first is a bit revy plus the big feet get in the way!, If I snap the throttle open & shut it seem's to knock it into gear and then won't jump out but this is a pain in the arse. Tightening the chain helped but not much. I not sure if I have a bent or worn selector fork.
Do you have kids too? I've been up since 6.30!

[KIYOSHI]

Kids rock! Scooby Doo and Ice Age for me at 7am

Have you measured each clutch plate on its own or the total stack height of all the plates as this is the number that is important. Also make sure the clutch is properly adjusted at the sprocket cover ( i wind the adjuster out, then in until there is just resitance and then back 1/2 a turn). Then adjust the cable accordingly.

Try some Barnett clutch springs and avoid anything EBC if possible (great for the road but not so hot on track).

Use the best quality semi-synthetic oil you can and not fully as it gets too thin when hot and has been known to cause problems. I use motul 5100T in my race bikes.

I have had a similar problem myself this year with the bike jumping from 6th to 5th under load and the clutch slipping on down changes. It was just a case of everything being in need of a re-adjustment.


Hope this helps

[dobbslc]

It's Ben Ten & Pepper Pig for me!
The clutch plates and springs are EBC, when you measure the stack height do you include the steels as well? I've seen Burnett clutch plates on ebay but they are about £100, how much are the springs?
All the adjustments are ok with half a turn of slack on the push rod and slack on the cable.
I did do an oil change after three sessions as I was running it in and used Silcoline fully synth 10-40 and it did slip more after this. I'm more worried about the gearbox as that will need to be stripped if there'a a problem inside.

[Stumac]

I was told by my engine builder to use Motul 300v 15w-50 on my new engine, this was new pistons, bearings etc. Basically all new including a new yamaha clutch.
My first time out on it the clutch slipped like buggery at high revs, I was not impressed! everything was adjusted spot on and was new so I was a bit confused.
After much discussion with Racetechniques I ended up changing my oil to Yamalube semi synthetic 10w-40 and everything was hunky doray, no more slipping.

I was having issues also when down changing sometimes from 6th, this all disappeared also, I was quite pleased as Yamalube is a bit cheaper that the 300v. Was also quite surprised when buying the Yamalube to be told that it is actually supplied by motul to Yamaha.

[rrsp]

sounds like you have a bent or worn out selector, as for the clutch slip use semi-syn oil, never had a problem !

[Taggyd]

yep a 14month old! no tv just feed me now or i'll scream the house down! though he does like the tennis and bikes on the telly! he's a good boy really!

i do all of the hairpin and bus stop in 2nd so never get down to first!unless its by mistake and then funny things happen to the rear end! weeeeeee!
sounds like the gear selector thingy then!lots of oils are made in the same place and branded as required by the customer, though the prices wouldnt suggest it!

[KIYOSHI]

Yes measure the stack height with the steels, add up what the total should be and see what yours compares like. Barnett springs are available from bike torque racing.