Anybody experienced gearbox failures after installing an automatic clutch (doesn't matter wether Rekluse or Revloc or EFM)?
The story:
After installing a Rekluse z-start into my TM300 I posted a review on our German bulletin board and told the people how much I liked it. At the same time two friends of mine also put z-starts in their bikes. One GasGas 250, which is mostly used for enduro riding and a KX250F which is only ridden on MX tracks.
Niels' GasGas and my TM still are just fine. Clutches work great and I have around 70 operating hours on it and Niels around 50.
The problem was the KX-F. My friend wrecked the gear wheels of the Kawasaki twice, both times when landing after a jump with the engine revs pretty high. Happened after only a handful of operating hours. The gear wheels simply exploded into shrapnel.
Our theory how this could happen is as follows:
Imagine you jump and the front end is too low. To cure this you open the throttle in order to make the engine rev so that the front end comes up again. With no resistance at the rear wheel (because you are flying high) the engine revs freely and the auto-clutch presses the plates together with maximum force.
In the moment you hit the ground your rear wheel is spinning with a speed that is good for, say, 70 km/h while you are in fact only moving with a speed of 50 km/h.
A manual clutch would now simply slip a bit to level that speed difference. The auto-clutch doesn't do that, because the pressure the (however many) steel balls produce is much higher than the pressure the six little springs in the manual clutch can put out.
So the slipping of the manual clutch works in this case like a shock-load absorber while the auto-clutch at max. pressure simply transfers the shock-load from the rear wheel to the crank. Then weakest part in the drivetrain breaks, which in case of the KX-F seemed to be the gear-pair that is currently working.
Another thing to consider (besides that I and Niels the GG rider don't ride MX) is that our bike have rubber-mounted clutch baskets, which might be able to swallow most of the impact. The KX-F has not. Same for KTM fourstrokes.
In fact KTM intended to include the Revloc to their Power-Parts program but quit testing after experiencing serious gearbox problems (same problem as I described above).
In woods riding it seems that all this doesn't happen, only when you are jumping and landing with high revs.
Another thing that is possible is that KTM's and Kawasuki gearboxes are a bit more fragile than others.
So, besides of what you think about our theory to the problem I'd like to hear some long term experiences from riders with auto-clutches who ride MX very often - especially CR450F riders, since another friend of mine put a z-start into his 450. He rides mostly MX and is now a little bit ancious (understandable).
The story:
After installing a Rekluse z-start into my TM300 I posted a review on our German bulletin board and told the people how much I liked it. At the same time two friends of mine also put z-starts in their bikes. One GasGas 250, which is mostly used for enduro riding and a KX250F which is only ridden on MX tracks.
Niels' GasGas and my TM still are just fine. Clutches work great and I have around 70 operating hours on it and Niels around 50.
The problem was the KX-F. My friend wrecked the gear wheels of the Kawasaki twice, both times when landing after a jump with the engine revs pretty high. Happened after only a handful of operating hours. The gear wheels simply exploded into shrapnel.
Our theory how this could happen is as follows:
Imagine you jump and the front end is too low. To cure this you open the throttle in order to make the engine rev so that the front end comes up again. With no resistance at the rear wheel (because you are flying high) the engine revs freely and the auto-clutch presses the plates together with maximum force.
In the moment you hit the ground your rear wheel is spinning with a speed that is good for, say, 70 km/h while you are in fact only moving with a speed of 50 km/h.
A manual clutch would now simply slip a bit to level that speed difference. The auto-clutch doesn't do that, because the pressure the (however many) steel balls produce is much higher than the pressure the six little springs in the manual clutch can put out.
So the slipping of the manual clutch works in this case like a shock-load absorber while the auto-clutch at max. pressure simply transfers the shock-load from the rear wheel to the crank. Then weakest part in the drivetrain breaks, which in case of the KX-F seemed to be the gear-pair that is currently working.
Another thing to consider (besides that I and Niels the GG rider don't ride MX) is that our bike have rubber-mounted clutch baskets, which might be able to swallow most of the impact. The KX-F has not. Same for KTM fourstrokes.
In fact KTM intended to include the Revloc to their Power-Parts program but quit testing after experiencing serious gearbox problems (same problem as I described above).
In woods riding it seems that all this doesn't happen, only when you are jumping and landing with high revs.
Another thing that is possible is that KTM's and Kawasuki gearboxes are a bit more fragile than others.
So, besides of what you think about our theory to the problem I'd like to hear some long term experiences from riders with auto-clutches who ride MX very often - especially CR450F riders, since another friend of mine put a z-start into his 450. He rides mostly MX and is now a little bit ancious (understandable).
