1998 gsx ltd compression test....

[mikeysso]

Last two weekends the ski was running great, went down over the past weekend and it wouldn't start. Cleaned the spark plugs charged the battery and im off and running, however noticed that the engine was shaking pretty hard when idleling. Also noticed a small noise being let off from the engine. Took the plugs out did a compression test and the front cylinder had real strong compression but the back cylinder was really weak. Any one encounter a problem like this or having any idea what the problem might be?

[Schwarzenegger]

If you pulled in any water in recent times, and it was forced through the cylinders...you may have thrown your crank out of phase. Or if your crank is spun out, the weak cylinder may have been detonating and blew a hole in the piston head.

[mikeysso]

is there a direct correlation between the two problems?
is it a hard fix?

[Schwarzenegger]

Actually yes, if you have pulled any water into the cylinders and tried to start it before pulling the spark plugs you will turn your crank out of phase. Water is pretty tough to compress Sometimes if there is just a small amount of water in the cylinder, it will let the engine roll over but because of the water in your compression chamber, it will force the crank to throw out of phase. The reason being, the crank will give before the water will compress ending in an out of phase crank. Sometimes it gets thrown out just enough to change it's timing just slightly most commonly resulting in advanced timing which works out to being detonation. If this is what has happened, hard to fix could be possible. You will have to pull the engine, give it a complete rebuild and either buy a new crank or send yours out to be re-phased. On top of which, the carbs will need to be cleaned...make absolutely sure there is no water in them. The fuel lines purged if the water is in your tank...and purge the tank too. It's an extensive job if that is what has happened.

[wmenzie2001]

Hi Guys
I have a 1998 gsx ltd, I bought it used last year and the previous owner just did a top end rebuild. I went out on the water last weekend and it just started to bog down. I put it on the trailer got it started(by pressing the throttle quite a bit) hooked a hose up to it and it idle fine for about 20 mins. I then proceeded to put it back on the water again and within 5 mins it bogged down again. I brougt it home and did a compression test "0" on the mag side and 90 on the pto side. Now my question is could this just be a dirty carb problem? Or does it need another new top end? Rebuilding the top end is my last option I want to make sure I explore every avenue first.
Thanks

[Seadoo timebomb]

You need to fix the fuel problem. Bad gas, old gas left in from winter, kills the engine. If compression test shows dead cylinder, time for a top end and at least a good visual inspection of crankcase crankshaft assembly. the bearings can get killed from prior water ingestion and crap getting in from piston failure. On rear piston failures, usually a result of lean condition from lack of fuel on that carb. the internal filter is clogged up solid with varnish from old gas and years of running and letting sit up over winter without changing gas for next season. You need to remove carbs, replace a lot of stuff which is covered all over the internet and on this site in several stickys. to do it right so will last another twn years aint gonna be real cheap, but nothing is anymore. If water has gotten in then you are up against the same issues to repair motor and need to go thru carbs to prevent the problem from happening, if not the cause this time. Throwing the crank out of phase is not nearly common as fuel issues and water ingestion that kills the pistons and/or rods/bearings.