99 GTX LTD troubleshooting question

[MoDawg73]

Hello all,
I have my Seadoo at the lake, and we have been enjoying it tons! She was running perfectly with one exception. After a pronged idle, or when just starting, she had a tendency to stall if you hammered the throttle. If I would gradually increase the throttle, it would sound like it was gargling, then it would take off. After this, full throttle starts from idle had no issues. She was running strong.

Today, I had a new issue. I had an extended ride. about 20 minutes at 4000rpm cruise, followed by an extended idle of about 25 minutes in a no wake river, then a 15 minute ride home at about 4300 rpms. About 1/4 mile from home, I decided to give it some more throttle. I felt the Raves kick in, and was cruising at 5100 rpms for about 1 minute. Then I thought, lets go WOT. so I hit it, but it behaved totally differently than it has ever before. It felt like it was surging between 5400 and 5600 rpms, but not able to get up to the 6400 that I had previously attained during similar short WOT runs. I brought it back down to 4000 rpm, and she ran like normal. When i slowed down to put her in the hoist, the idle was significantly lower than normal (1200 vs 1400 normally).

The only other thing I did was unscrew the gas cap, to see if it was pressurized. It did not have any pressure, which it typically has.

I pulled the plugs, and this is what I found.




I am on a fully rebuilt engine with 20 hours on it. Fully rebuilt carb with Mikuni OEM parts, including Needle and seat. Fully switched out fuel lines, selector switch, filter, and O-ring. Pressure tested fuel system.Changed pump oil, bearings, and seals. Cleaned Oil Tank. Replaced oil lines and filter. Use only Seadoo fully synthetic 2-stroke oil.

Any thoughts would be great! Thanks so much!
Ken

 

[JeremyD615]

Well from what you’re describing and the appearance of those plugs, you’re running really lean. I would suspect that you’re getting an air leak somewhere in the fuel system... Get a piece of fuel line and run it from the reserve nipple directly to the carbs and see if that fixes the issue. If it does, hook that line to the water separator and try again. If it acts up with it running through the filter, replace it. If it doesn’t, replace the fuel selector.

I know you have already gone through those parts, but you’ve got air getting in somewhere, so we just need to figure out where it’s getting in.

 

[MoDawg73]

Gotcha. Thanks. Will do

 

[MoDawg73]

Ok,
Pressure tested the fuel system again. No leaks with the selector on OFF, none so far with it on ON (I’m 4 minutes in)

Also, the gas cap did let out some pressure last night when I put it to bed.

So if it isn’t a fuel system leak, what would I check next?

When I put on the carbs, I got a little crossed up, and the carb base gasket got folded up on itself, leaving a small crease. I just unfolded it and installed it correctly.

Would this crease cause a lean running condition?

Should I do an idle test with new plugs and pull the plugs to see if she is running lean or rich at idle?

Should I consider adjusting the high speed adjust to riches the mixture?

I was also almost out of gas when the surging happened. Could this cause it? With gas sloshing back and forth would the pickup only be in contact with the gas some of the time?

Those are my thought and questions. Any thoughts you have would be greatly appreciated!

Ken

 

[JeremyD615]

You really need to do the bypass procedure I spelled out above. The fuel system works under suction rather than positive pressure, so sometimes they will hold pressure, but still leak under vacuum. The pressure test also doesn’t account for a clogged selector, as it will still hold pressure even with a completely clogged line.

The carb base gasket could be a problem, but if that were the cause, you’d only have one lean plug.

I also don’t think it’s from the low fuel level, as those plugs look like they’ve been run lean for a while...

 

[MoDawg73]

Thanks!