1999 XPL - Acceleration Issues

[JonRusso89]

99 XP Limited.
Here's the deal: Idles perfect, and runs high RPMS perfect, the problem occurs during acceleration. Regardless of whether or not you roll on the throttle slowly, or punch it wide open, it hesitates between 3000 and 4000 RPM's. After a few seconds it planes and takes off and quickly hits over 60 MPH on the GPS. It is NOT cavitating.

- Compression good
- Changed Plugs
- All fuel lines replaced
- Fuel filter cleaned
- Fuel selector cleaned
- Carbs cleaned thoroughly
- Carb adjustments set to spec
- Pop off pressure - 20 psi in both carbs (good)

Cleaning the raves is on the agenda for tomorrow, but being that the issue is at lower RPMS my gut is telling me it may not resolve the issue. What do you guys think?
Thanks

 

[Dr Honda]

Could be the RAVE's hanging.
Could be the water regulator.
Could be a case leak in the engine. (A leak down isn't easy to do, but may need to be done)

You say the compression is good. What was it? (MAG and PTO)

 

[JonRusso89]

I believe it was about 143 MAG and 145 PTO? It was a couple weeks ago, I'll do another one tomorrow and write down what I get. I'll be cleaning the rave's tomorrow, would you recommend cleaning the water regulator as well?
Thanks

EDIT to ADD - My original description of this being an acceleration issue may have been misleading. The problem also occurs if I am letting off the throttle. It runs fine until it hits 4000 rpm, and then becomes rough as if it is missing on one cylinder. Once it reaches roughly 3000 rpm it smoothes out and then idles fine.

Dr. Honda - does this at all change your initial thoughts? Thanks for the reply.

 

[Dr Honda]

Normally, coming down from high RPM's... that would lead me to believe it's carbs. But, I would still look at the other things. When you skip things... you cant be sure of where the problem is.

If you have a dead spot at 4000 rpm's... either up or down... I would think that either the high speed check valve is leaking... or the transition ports are plugged.

Please read this:

http://www.seadooforum.com/showthread.php?33643-Even-the-Pro-s-screw-up-once-in-a-while.

 

[JonRusso89]

Thanks again for the reply. I have been leaning towards the carbs also. But I have had them apart a few times now and can't pin point an issue. Transition ports were my first suspect but I have visually verified they are clean are clear. Thanks for the link, I always try to keep that in mind. I'm not familiar with the high speed check valve, I'll have to check the shop manual. Thanks again.

 

[Dr Honda]

The high speed check valve is behind the "Jet Block" in the carbs. It's just a Mylar flap on the back side.

Something else I just thought about. Since you have a reed engine... you may want to pull the reed blocks and look for any damage.


As far as the air box parts... as long at the flame arrestor is in it... then the "Tuned" air resistance should be OK.

Last thing... If you held the throttle at the dead spot... would the engine die?

 

[JonRusso89]

No it will not, if you hold it at the dead spot it will not bog or die. It sounds as if its only running on one cylinder if you hold it there. Once it gets past roughly 4k it takes off.