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Clutch slipping?


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Gentlemen,

 

I've got my bike going for a little while now, it has a lock up clutch, and it all works well.

 

Yesterday when I was out riding a couple of times happened that the engine revved up, first I thought that the back wheel lost grip. It happened at about 120km/h in 5th gear when opening up the throttle.

Thing is, I didn't notice anything on the ass end of the bike, no back wheel what stepped aside or a bounce in the seat. The engine sounded like it was working, under load.

I'm pretty sure it came from the clutch, because when I give it to her in 3rd and 4th the rear wheel doesn't lose grip, it was just a bit in 5th.

Usually when a clutch starts slipping the engine revs up and sounds like it's not under load.

 

Does it happen more often with lock up clutch that they start slipping after a while?

And with a lock up, does the engine sound different with a slipping clutch as with a normal clutch?

Clutch plates are only 6000km old.

 

Thanks

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Most Lock-up clutches on Turbo road bike have been fitted to beef up the stock clutch and stop slip and not what they were originally designed for  "Drag Racing" 

Give the symptoms you describe it sounds like it may need a little bit more weight on all or some of the lock up arms ..

This assumes it was fitted with the correct air gap and some weight,s to start with ? 

 

By Weight i mean "Nuts, Bolts and washers"

Edited by Duckndive
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2 hours ago, Reinhoud said:

I know the solution, was wondering if it happens more often, a good clutch what starts slipping out of the blue.

Don't think it can be caused by wear already..

not as a  rule .....i would say it was a little light on weight when installed and now the plates have bedded in under the right conditions it slips a bit...

i used to run my turbo efe on 3 stock springs with a nut and bolt on 3 arms and a bolt with 2 nuts on the other 3 arms....one finger pull on lever

1.60 - 60 fts and no slip on road  

Caveat but not all bikes are the same on that set up O.o 

Edited by Duckndive
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There seems to be always some amount of black magic involved with the clutches :P

A lockup on a turbo engine complicates things a bit more. Since clamping force depends on rpm, the clutch shaft rpm to be precise, you may need quite hard setup if the boost and torque come up early. At mid / low rpm there isn't yet too much centrifugal force on the arms so you may need quite a lot of weights and base springs to make it hold full torque. That also brings up one more variable for clutch slipping. If you make boost a bit earlier on one day, for any random reason like weather change, it might be enough to make the clutch slip.

I have also had that kind weird occassional slips sometimes. Usually if the setup is on the edge. Oil temp seems to be one variable, it slips easier at low oil temp. Like mentioned the cure is to use more weights and springs. And naturally making sure that everything is in good condition in the clutch.

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5 hours ago, Arttu said:

There seems to be always some amount of black magic involved with the clutches :P

A lockup on a turbo engine complicates things a bit more. Since clamping force depends on rpm, the clutch shaft rpm to be precise, you may need quite hard setup if the boost and torque come up early. At mid / low rpm there isn't yet too much centrifugal force on the arms so you may need quite a lot of weights and base springs to make it hold full torque. That also brings up one more variable for clutch slipping. If you make boost a bit earlier on one day, for any random reason like weather change, it might be enough to make the clutch slip.

I have also had that kind weird occassional slips sometimes. Usually if the setup is on the edge. Oil temp seems to be one variable, it slips easier at low oil temp. Like mentioned the cure is to use more weights and springs. And naturally making sure that everything is in good condition in the clutch.

Ach, of course! Didn't think of that..

 

I turned the boost dowmn, and advanced the ignition, that makes the bike more agressive, better throttle response.

Thing was also what made me doubt, when the clutch was slipping, the engine sounded like it was under a lot of load, and that's usually not the case, but maybe that's because it's a lock up?

 

Edited by Reinhoud
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9 hours ago, Reinhoud said:

Thing was also what made me doubt, when the clutch was slipping, the engine sounded like it was under a lot of load, and that's usually not the case, but maybe that's because it's a lock up?

Yes, a lock-up seems to do that if it isn't slipping too badly. So revs shoot up a bit but not to the limiter and once the bike has collected some more speed the clutch will hook up again.

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  • 1 month later...

Update;

 

Yesterday I could be bothered to have a look at the clutch ( I blame the alcohol).

When I took the cover off I smelled there was something off straight away, I put about 15 grams extra weight on the lock up, but when I took the pressure plate off, I wanted to see if there was anything wrong in the clutch, I noticed that the fibre plate was blackish, I've got red/orange plates.

I put a steel plate between the fibre plate and the pressure plate and the slipping is gone

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