97 Seadoo XP backfiring

[Skirta]

I have a 1997 Seadoo XP that I brought back to life. New MPEM, new (used) and rebuilt carburetors, new fuel lines, new fuel switch, new fuel filter, new starter, new ignition coil, rebuilt oil pump, and new plugs.

It ran fine for a while but now it is running really lean and backfiring horribly. If I try to run it at WOT it leans out enough to die or barely runs at all. It isn't shooting oil out of the pistons so I think the inner crank seals are fine.

There is oil in the hull but I spilled a bunch in the oil pump rebuild so I can't tell if one of the outer crank seals is the problem. Basically I'm at my wits end because I can't figure out why it started doing this.

Any help or suggestions are appreciated. I've done all the repairs myself so far and I grew up around two stroke engines so I think the work has been done right so far.

 

[burtshaver2021]

Where did you buy the fuel selector valve from? Try running a fuel line direct from the fuel tank ON fitting to the carb. Maybe sucking air from the new selector for valve or the fuel filter/seperator

 

[mikidymac]

Is it backfiring out the carbs or exhaust?
Are you testing it in the water or on the trailer?
Has it ever run correctly?
What is the compression?

 

[Skirta]

Where did you buy the fuel selector valve from? Try running a fuel line direct from the fuel tank ON fitting to the carb. Maybe sucking air from the new selector for valve or the fuel filter/seperator

I'll have to test it tomorrow but at least on the trailer that seems to have helped for the 15 seconds I ran it.

 

[Skirta]

Is it backfiring out the carbs or exhaust?
Are you testing it in the water or on the trailer?
Has it ever run correctly?
What is the compression?

Is it backfiring out the carbs or exhaust?
Are you testing it in the water or on the trailer?
Has it ever run correctly?
What is the compression?

It is backfiring out of both but more carbs than exhaust. Tested both in and out of water. It ran correctly briefly last winter but I'm not sure how as the old fuel selector was clogged, the fuel filter was clogged, and the fittings on the old carb were broken and leaking fuel. The compression is well over 150 on each cylinder.

As suggested in another reply I tried running a fuel line directly from the tank to the carbs and it seems to be running better. I will water test tomorrow. If that's the fix I may throw an inline filter and just live without the selector. It only runs on a a small lake and in a worst case scenario I have another ski to drag it back.

 

[burtshaver2021]

It is backfiring out of both but more carbs than exhaust. Tested both in and out of water. It ran correctly briefly last winter but I'm not sure how as the old fuel selector was clogged, the fuel filter was clogged, and the fittings on the old carb were broken and leaking fuel. The compression is well over 150 on each cylinder.

As suggested in another reply I tried running a fuel line directly from the tank to the carbs and it seems to be running better. I will water test tomorrow. If that's the fix I may throw an inline filter and just live without the selector. It only runs on a a small lake and in a worst case scenario I have another ski to drag it back.

Don’t run an inline filter, if it fixes your problem, try running the line from the tank to the fuel filter/seperator and then from there to the carb. The inline filters cause problems for these machines, especially the paper filter, filters. If your OEM filter is sucking air, the square o ring for them is only a few dollars