XP650 top end problem

[skodatomek]

XP650 top revs problem

Hi Guys!
Got same problem all summer
Irregular run over 4000 rpm max 6200 but then backfired
Up to 4000 runs like hell!!!
No problem to start.
But on water only goes up to 4000 (I can run it for hours like that)

This is a list what I did up to now:
* carbs cleand and adjusted (I can do it with closed eyes lol, did it so many times)
*new battery
*new fuel lines and fuel filter
*tank removed and cleaned
*new spark plugs
*compression on both cyl about 12,5

Is there any thing else what I should check/replace?
Thanks

 

[skodatomek]

Been on the sea yeasterday. Ski perform well up to 4500 revs (goes over 6000 when jump). After 4 hours I've used all pertol. Don't think it's rectifier cose battery is fine.
Any ideas?

 

[timmyboy76]

quick way to find out, is disconnect the red wire at the rectifier, then give a try.

 

[jhjesse]

Timing?????

When you took the carbs off did you remove the intake, as well?
If so, did the rotary valve come off the splined rotary shaft?

 

[skodatomek]

No, I have removed four bolts which hold carbs to "intake manifold" only, but when the problem with carbs occured for the first time, I took the flywheel off to see if the ignition coil is not damaged in any way. And it did look well. They have been removed and fitted back (believe back in correct position, doed it really matter?) Also think somebody did that before cose coils got some marks left by bolts from the flywheel puller.
I will try to disconnect that red wire and then I will let you know.
Thanks for help. Fingers crossed

 

[skodatomek]

Just to clarify/confirm.
Is it the red wire, which have to be disconected?
Thanks

 

[timmyboy76]

yup///the "silver" 1in block thats turned sideways, with the yellow face...follow the red wire from it, and disconnect.

 

[skodatomek]

Faild
I did try everything, and it's time to give up
My "sea don't" is is on eBay as spares/repair

Thanks guys for all your help, and advice.

skodatomek

 

[6KJR]

I think its your carb settings themselvs. I would check your spark plugs and see how they look when you are running at your max RPM. Backfiring is not good and could be that you need more fuel on the top end.