Yesterday, I was riding, 15 miles into the ride on my '02 Viper, I completely blew my belt. It was new this year with apprx. 150miles on it at time of detonation. When it blew, I was moving across a field at Wide Open Throttle. I don't know exactly the rpms at the time, but when it blew, I was off the throttle, but the engine was revving at 9K rpms(SLP pipes, Hartman clutching) all on its own. I was off the sled and after turning off the key and then the kill switch, it still wouldn't idle down or shut off, just revving at 9K rpms. I finally stopped the motor by hitting the choke. Any ideas as to why the motor would rev on its own, and then wouldn't shut off? After crushing my belt guard, and replacing the belt w/ my spare, it started fine, and idled at normal rpms upon restart. Although everywhere we went, the idle was hanging at the 3-3400rpm range even prior, until after apprx. 8-10 seconds it would idle then down or if I hit the choke. Apprx. 25 miles later while crusing down a seasonal road, apprx. 55-60mph, the sled started slowing down, and losing power, when the motor then made a "ting" sound and shut off. Seized. Upon pulling the center jug off, the piston was turned sand on the edges, mainly by the exhaust, and the rod came off with the piston. A lot of bluing by the rod, apparently got really hot where it connects to the crank. Would the few seconds that it was turning 9K rpms w/o a load on it, devasate the crank? After I blew the belt, the motor didn't seem to be riding right. Didn't seem to pull hard at the top end, and seemed to fall off. Is that the sign of a lean mix. I believe I have 165 mains across the board, w/ a Peak Performance head, 22 cc, and a rear cooler. After reading a few recent posts, by the incessive high idling, it was lean at the lower end? Any carb suggestions for my next motor. Please help, season just started and I'm down a motor already!
When your belt came off and your motor stayed at 9k rpm this is what is called a lean runaway. When there is no way to load the belt or to put a load on the motor for that fact, the fuel charge is so violent that the motor runs away. Seen this happen with high performance Jet skis.
Now when you said you could not shut it down with the kill switch or the key says that the tops of the pistons were so hot that the motor was detonating and the fuel charge was being being ignited by the heat alone, kinda like a diesel. This is why the choke shut it down, because you flooded (so to speak) the cylinders with alot of fuel that helped cool the piston tops to stop the dieseling. In otherwords the metal was so hot inside the cylinder that it was glowing.
Either some where in that motor you have an air leak, like a bad seal, or if the motor/crankcase was apart you missed a section of the sealing surface with sealer somewhere before re-assmbly and or the the carbs are dirty...
What cylinder does the pulse line go to t connect the fuel pump??(center I think - I don't own that sled) If it is the center cylinder it may be possible that there is either a hole in the pulse line or the pump may have gone bad causing you to suck air and leaning out the fuel mix causing your problems. A rod will not turn blue and destroy itself if a motor runs at 9 grand for a few seconds, it means that there wasn't a proper amount of lubrication for a bit. Hope this helps. T
Now when you said you could not shut it down with the kill switch or the key says that the tops of the pistons were so hot that the motor was detonating and the fuel charge was being being ignited by the heat alone, kinda like a diesel. This is why the choke shut it down, because you flooded (so to speak) the cylinders with alot of fuel that helped cool the piston tops to stop the dieseling. In otherwords the metal was so hot inside the cylinder that it was glowing.
Either some where in that motor you have an air leak, like a bad seal, or if the motor/crankcase was apart you missed a section of the sealing surface with sealer somewhere before re-assmbly and or the the carbs are dirty...
What cylinder does the pulse line go to t connect the fuel pump??(center I think - I don't own that sled) If it is the center cylinder it may be possible that there is either a hole in the pulse line or the pump may have gone bad causing you to suck air and leaning out the fuel mix causing your problems. A rod will not turn blue and destroy itself if a motor runs at 9 grand for a few seconds, it means that there wasn't a proper amount of lubrication for a bit. Hope this helps. T
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mopar1rules
Active member
just curious what brand of belt you blew? also, you said that the edges of your piston are pitted and sand blasted looking? if so, that deffinetly is signs of deto. what octane fuel were you using?
I actually don't recall the name brand of the belt, but it was a non-Yamaha belt, supposed to be a softer compound for less slippage. Cost me a good buck. I was running 93 Octane. Thanks for the help.
mopar1rules
Active member
yeah, i was figuring it was an aftermarket belt, cause i've never had any luck either w/belts other than yamaha. your 93 octane fuel should have been fine. you might want to up your mains to 167.5 or even 170. what are your pilots, nozzles, and needles set at. i noticed your mechanic buddy said to check the plugs by going wide open and killing engine. that will tell you the plug color and how well the mains are, but not the pilots, or low end. you need to let the sled idle for like 15-20 sec. kill engine and check the plugs then, but if you get hanging idles, you need to up the pilots or back out fuel screws.
mod-it
Member
Assuming the carbs were cleaned before started riding this year...
Yes the carbs were cleaned this year. The pilots are stock and the needle was set at 3.5 I believe. The fuel screws I can't remember, until I tear down.
mod-it
Member
I'd look for air leaks and check seals then.
SRX M10
New member
Sounds like an air leak to me, carb boot??? crank seal???
