99 SeaDoo GTX RFI spark question

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Disabell

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I have a 1999 SeaDoo GTX RFI that is turning over but won’t start. I took one spark plug out and it will start on one cylinder. It appears to not be letting any exhaust out when the spark plug is in. Any ideas?
 
The spark plugs have nothing to do with the exhaust.

Have you tried installing new spark plugs?

Is the fuel fresh?

Probably most important is have you checked the compression in each cylinder with a compression gauge?
 
I have changed the spark plugs, new fuel, and checked compression, all is good. With one spark plug out it will run. When you cover the hole of the removed spark plug it begins to stall and will not restart with both plugs in. I’m thinking it’s an exhaust manifold or valve issue not allowing air in and exhaust out.
 
2-strokes do not work that way, there is no exhaust valve.

What were the compression numbers?

The next thing I would check is the rotary valve clearance and condition.

Also keep in mind the RFI skis only idle on 1 cylinder but I don't remember if it is the front or rear.
 
1999 SeaDoo GTX RFI, having this exact same issue, (starts with front plug out, but not when in) ordered new fuel injectors, fuel rail, and fuel pump complete assembly, the injectors i pulled out looked really bad, thinking the front injector wasn't working properly which is why i ordered 2 new ones, when i pull the front plug out, it starts and runs good (on one cylinder) when i put it back in, it wont start... did i do the right thing by ordering these items?
 
As Miki Said..... May be a rotary valve issue as one cylinder seems to be affected the other. That said, compression numbers are essential before moving forward. I have a 1999 RFI that appears to idle on both cylinders. I had a fouled plug which I replaced and idle speed perked right up.
 
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