SJ 650 Engine problem??

[hobie164]

My 650 starts and runs up till around half throttle. It then acts almost like it is hitting a rev limiter. It has good battery connections, good fuel, rebuilt carb, compression and I just replaced the CDI. What else could it be, can I test for?

 

[BBYamaha]

could be coil, mine with a b pipe, would get up to 3500 rpms pretty easy then just stay there, a pretty good way to check if its only running on one cylinder, run it for a minute on the water, open the hood and feel the cylinders and see if one is hot and one is not, could be a fouled plug. Its pretty common with with the superjet 650 coils to go bad, I cut my 93 wire open to see it was corroded from end to end, replace it and it ran great since, the other day I had a boot come loose in transit and it ran like crap till I popped the hood :kabong:and saw the wire laying there... or your over heat sensor may be bad as well, heard they go bad often, mine still works fine and have never had a problem with it or seen a problem with it on any of my buddies square, another possibilty is the stator, they present some odd symptoms but i would start with coil and work your way to the less common problems

 

[MADMAT]

Why did you replace the CDI?? And where did you get it? New? Used?

That sounds like CDI to me.

I have never had a coil go bad ever. Just plug wires.

Could be stator too.

 

[BBYamaha]

I say coil go bad wires is what i ment and unless you are JSS or the digler ( I think he is the one that likes to splice sorry if not him ) Wires go bad since there is alot of water in them at least all the squares I have come across, most of which the seals have been neglected... my wires(in my 93) were broke every inch and corroded all the way to the base.