2000 XP 951 midrange surge

[69boss]

Owned this PWC for over 10 years. Last year it developed a surge from 4200 to 4800 RPM. If you brought the throttle up to 4200 motor will slowly [about 5 seconds] raise to 4800 with stationary throttle, same thing happens slowing down. You have to constantly work the throttle lever to maintain the same speed. It isn't a misfire, the engine runs well at all other speeds and throttle positions. Carbs were clean without corrosion or any other visible issue. Have just been rebuilt by an experienced watercraft shop, but they don't know what is causing this. I haven't messed with any of the jet adjustments yet and don't know where they are set. Any suggestions? Thanks.

 

[mikidymac]

This is pretty typical on the 787 and 951 at that rpm range because it’s the rpm that the rave valves are either opening or closing so the port timing is changing.

You are basically trying to hold an exact rpm at the time the engine is transferring from low speed port timing to high speed.

 

[69boss]

Yes, trying to hold RPM. The surge is at the speed I like to cruise at. Have had 4 of these over the years. This one was may favorite as any surge was minimal, now not so much. Something changed with use or age.

 

[Mraw]

Did the shop you take it to clean the raves? Maby before they were gummed up a bit

 

[69boss]

No, Will check them, thanks

 

[69boss]

Thanks for the suggestion. The valves were somewhat dirty but found a broken spring in one of them. That should effect operation. Will find out Friday.

 

[POPPS]

And that is not a stock spring for sure,,.that is why it is broken

 

[69boss]

Originals don't ever break? I didn't buy this new but everything visible is stock. Why would someone change them? Did buy a couple NOS springs today but won't have them for a week. Was going to rob a couple off another XP for this weekend.

 

[1of500]

Keep in mind the 951 and 787 springs are different strengths. 787 being stronger since the 951 works off the solenoid and crank pressure

 

[1of500]

I've had oem break

 

[69boss]

Keep in mind the 951 and 787 springs are different strengths. 787 being stronger since the 951 works off the solenoid and crank pressure

Taking it off another 951, thanks

 

[69boss]

Took it out yesterday the rave spring fixed it. Thanks