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Discussion Starter #1
So i bought a used 05 mxzx 440 chassis 600 motor. The ad stated it had a 08 rs motor. Not sure if its true as the guy i bought it from didnt do the swap after owning it for 2 seasons. Anwyays i fired it up upon viewing and it reved to 5k rpm for about 20 seconds then to 3k rpm. Took it out for test drive after he had , had out for the day 20 miles on the lake. So i bought it as it ran fine. Today i took it to my garage to unload from my pick up and when i fired it up it reved straight to 7k rpm an almost coming off my pickup but i had my hand on the break luckily. So i managed to get it into garage and change the plugs and i fired it up an it reved to 8k rpm ! What the heck it almost want to take off thru my wall. So i immediately shut it off. Put the old plugs in and fired it back an reved to 8000 rpm , and then a squealin noise came out of no where. Is this a belt an clutch problem ? This machine scares the shit out of me idling at 8000 rpm and smoking my belt. Need your guys geniuses minds !
 

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Not a belt issue. Throttle issue. Does it have a riser on it? Could be the cable is stretched if it does.

Seeing as it is a mod sled, there are a bunch of possibilities, but I'd start with the throttle cable.

In order for it to rev, it has to have air and fuel in the proper ratio. To much fuel and it will slobber on itself and not rev up. To much air it will seem like it is running great until it gives out. In this case, it just sounds like the carb slides are not closing. Since it revs up that much, I'm betting that both carbs are open, which means the problem exist at or above the split in the throttle cable.

That said, if it has a throttle extension cable, it could be one of the little boxes that tie the cables together is sticky.
 

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Discussion Starter #3
It does have a 5 inch riser an stock bars , cable length seems okay. Started it up today and it reved to 6k rpm but then i notice the primary sticking as the belt was rubbing an disnigrating on one side and causing it to rev to higher rpm. So im going to have to clean the primary i assume , add new belt , set deflection proper. Hopefully that works. Ill also seafoam the gas tank as it sat all summer and only bin out once this winter for 20 miles mabey thatll help and add fresh gas. What do you guys think?
 
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