suzuki eiger engine rev problem please help!

[mrbocifus]

I am having an issue with my eiger 400 ability to rev while in forward or reverse. I have cleaned the carb. It sounds like it revs out fine in neutral. When you put it in forward and proceed to accelerate it will start to cut out at about 10-15 mph. It's like the reverse rev limiter is kicking in. Could this be a vacuum leak? The valves seem to be adjusted properly, so I don't think that would be keeping it from revving. Could it be a bad ECU? Is there a way to check for a properly functioning ECU?

This is not my ATV, I am just looking at it for a guy. It has the air box lid removed and I asked if the ATV cut out the same way with the air box lid on and he said it did. So I am assuming that can be eliminated.

Any advice would be much appreciated.

[lt230sman]

wow, thats a tricky one.

i'd try cleaning the carb since it's easy and your problem very well may be related to loaded operation (neutral does not provide this).

good luck

[Phil05Eiger4x4]

put your fuel valve on RES or PRIME and i bet it fixes the problem something with the vacum on those go bad but try that and let me know what happens