1999 Gsx misfire or cavitation that only happens at full throttle whenever going straight not turning...

[dookyle87]

Ok first of all thanks for checking out my post

I've got a 99gsx rfi
I've been chasing this weird hesitation problem for two years.

When it does this: only at wide open throttle while going straight. At partial throttle it runs fine and at WOT while turning it also runs fine no hesitation.

What I've tried:

New rectifier , nope
New tps. Nope
Throughly cleaned raves nope
Performed tps reset with candoopro nope
New plugs nope
Took the air box and spark arrestor off nope
Ran with seat off nope
Cleaned and tested injectors nope

Now I'm thinking maybe it isn't a misfire but maybe intermittent cavitation? Rrrrrrra titaaaaaatitaaaaaaatitaaaatititittitaaaa only at wot while going straight it doesn't misfire or hesitate at all when turning What do you guys think? I'm thinking slight cavitation and it builds back pressure in the pump when turning which negates this?

Meaning a wear ring replacement or prop or both I assume

 

[mikidymac]

Have you replaced both in tank fuel filters yet?

That would be the first thing on my list.

Also don't run without the air cleaners and box or it will be too lean, you need the restriction.

 

[dookyle87]

Have you replaced both in tank fuel filters yet?

That would be the first thing on my list.

Also don't run without the air cleaners and box or it will be too lean, you need the restriction.

I'll try the fuel filters next where do I buy them any idea?

 

[mikidymac]

Do a search here on the RFI how to as they list the part numbers and everything from Autozone.

Here is the link and the part numbers are in post #2.

RFI Info

 

[Chester]

It's hitting the rev limiter. Inspect your impeller and wear ring very closely. Remove the jet pump.

Chester

 

[Chester]

It's cavitating.

Chester

 

[AKnarrowback]

First thought is you are looking at a pump problem. But my experience is only with early generation DOOs and not rfi. If it was one of mine the first thing I would do is pull the impeller out and see if the trailing edge is bent forward from rocks going through.

 

[dookyle87]

you guys were right the leading edge of the impeller was nicked up and the pointed parts at the end of the impeller were actually flipped up!! A pair of visegrips as a little patients and a belt sander along with a new wear ring and it's good as new

 

[AKnarrowback]

Good to hear, a simple fix is always good.

A bent up trailing edge, in my experience, shows up as a bump on the rev limiter running in a straight line wide open. Low end and in turns with a good load on the motor keeps the rpm's down and it doesn't show up. The 91 and 92 XP had the rev limiter set too close to the top rpm and they were sensitive to bent impellers or a rev limiter that engaged a little too soon. The fix for the rev limiter was, just as you did, a slight "adjustment" to the trailing edge with a crescent wrench to increase the impeller pitch.

 

[twalli]

I don't mean to hijack this post but I am having a similar issue with my 1997 GTI. The engine seems to respond appropriately to varying throttle inputs but there seems to be a lag in the translation to putting down power. Here's a video that I took last weekend that kind:

This seadoo belongs to my family and I haven't driven it in a couple years but I know that it feels like it's slipping or cavitating and isn't performing like it should.

I was told to check the drive shaft splines because that was a common reason for this slippage. I'm no expert but they look fine to me (?)

I saw in the previous posts about a dinged up impeller possibly being the culprit. I see one of the blades has a pretty good ding but I'm wondering if it is big enough to cause the issues that I am having (?)


I'm wondering if it makes more sense that the issue has something to do with the seal between the jetpump and the housing but I'm not sure. This what it looked like when I pulled it off last night:



I'm hoping to get this thing working again soon so that I can sell it for my family. Any input/advice is appreciated!

 

[jts32]

You need a new wear ring and pump seal

 

[mikidymac]

Yes, it is painfully obvious your problem is the wear ring. Yours is missing all of the rubber that the impeller rides on and is just the outer fiberglass support left. You need a new wear ring and a neoprene seal. No silicone should be used.

And no. stripped splines are not a common cause of cavitation.

 

[twalli]

Thank you both!