Thread: Busted clutch question
07-17-2010, 04:38 AM #1
Busted clutch question
I blew my clutch today . Had to limp the ski home at 5000 rpm.
Got a theory as to why it blew just want your imput as if my thinking is correct. Its a long post but please read and add any imput if you can guys.
Its got all the Riva stage 1 kit, Watson blow-off valve, ETss low boost wheel 13.5 psi at 8400 and 11.7 at 7700, ntercooler upgrade kit, Motec ECU.13/23 skat.
I first put all the mods on before I got the Motec and the ski ran really hard on the stock limiter for a few rides and was poping loudly. Once I fitted the Motec and repitched my prop to stay just off the limiter the poping sound has stoped.
I have only put 1 hrs on the motec and the clutch went out today. I am carefull not to hold full throttle for too long and to release it smoothly and when in choppy water not to work it too hard. You can hear the blow-off valve doing its job when you get off the throttle or going through chop.
Could I have already caused the damage from riding the ski for 5 hrs with all the mods and the stock ECU and could the clutch have worn out by bouncing the ski hard of the stock limiter when full throttle?
I hope this is what did it to the clutch and now I have the ski with higher limiter and prop pitched to stay of it that the blow-off valve will protect the new clutch.
When it was boumcing savagly off the stock limiter the ski was poping loudly from the back but the blow-off valve was not dumping pressure, so my thnking is that this was causing high loads to the sprag clutch causing excessive wear.
Is this thinking correct?
07-17-2010, 05:57 AM #2
You're on point...but before you go buying a new sprag look into the supercharger and find the root cause. I bought a sprag when in fact I broke a supercharger shaft. All I can say is hopefully its the sprag bearing and not the gear breaking like my situation or you will be looking at big money to ensure your motor is good to go. Keep us posted and don't buy anything until the root cause is explored.
07-17-2010, 06:22 AM #3
The first 20 hrs from new on this ski the mechanic had only put in synthetic oil in and I have since found out that it is no good for these sprag bearings.
I put in the genuine yamalube and filter when I fitted the Motec 2hrs ago.
Maybe the synthetic caused the sprag wear?
I am sure its the clutch as when we first went for the ride today I noticed on hard acceleration it would start boosting hard and when it got to about 7400 rpm I noticed for say a second that it would hesitate then it would boost hard upto say 8400 rpm. It did this on a couple of full throttle hits today and on other accceleration hits would perform hard and good.
On a full throttle run back home when I got of the power and went to accelerate again thats when I noticed no boost and max of 5500rpm.
Its kinda like the clutch was on the way out today for say 2 hrs till it finally went.
Hopefully its not what happened to you with the shaft and I won't have to kill the mechanic who initially commisioned this ski.
07-17-2010, 07:35 AM #4
07-17-2010, 07:45 AM #5
There was a long discussion on the forum about the oil being the root cause. Not so. The general answer is that no matter what oil ( I have used synthetic for 20+ hrs), or mods you have, your clutch will fail. Just a matter of when. Some with 10hrs, some with 40hrs, some have gone more.
07-17-2010, 05:25 PM #6
I think we willnever know and the real problem is these clutches are just shit.
Hopefully someone comes out with a better one real soon otherwise these skis are more useless than any other.
07-17-2010, 05:33 PM #7
07-17-2010, 05:38 PM #8
I must have had a Friday afternoon built unit.
22hrs is not good. I will try another and if it fails the ski will be sold.
Maybe my surf jumping did it no good.
07-17-2010, 05:39 PM #9
Does anyone know if Yamaha is coming out with a better replacement real soon?
07-17-2010, 08:09 PM #10
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