time for top end rebuild?

[ddanster]

I have a 1998 gtx limited and did a compression test. I have 127 and 140 psi on cylinders...probably time to tear apart? It does idle kinda rough in the water but still has good power...it can sometimes be hard to start in the water though.

Thanks

 

[Dr Honda]

Yes... it's a good time to freshen up the top end. Since you decided to do it before a melt down... you can probably just replace the pistons, and rings... and not even need to bore it. (but measure the cyl's first)

 

[ddanster]

Thanks...a turning wrenches i go

 

[SabrToothSqrl]

Will the 15 year old crank be up to it? How many hours did this 951 last and what oil did you run?

I ask, rhetorically, from experiencing crank failure after installing a new top end... So you get to do all the work... All over.

Just something to consider.

 

[bell99man]

If 135 is normal for this engine, and given the 5% off accuracy of many gauges, is it really ready for a top end? It seems well within range. Is he the original owner and know how many hours are on it or has there been a rebuild on it before? Could it be fuel or spark related? Don't get me wrong Dr. You are by far the expert here but it just seemed like a quick answer without much info. I'm just learning here so why is it ready, the difference in the two is nearly 10%? I hope I don't sound like a jerk or a wise crack because that is not the intent. I just want to know how to evaluate these in case I pick up a GSX limited in the future.

 

[SabrToothSqrl]

I think I remember 10% between the two being the rebuild threshold, however if I was running that ski, and it still hit 7K WOT under load, I'd just run it till it stopped working, then rebuild the thing... I'm not sure that doing it now will really save anything... But, his choice.

The difference between the readings is the indicator. The gauge may be off, however it should read the 'same' inaccuracy for both pistons... so.. you are looking for the difference between MAG and PTO... which, in this case, is rather large.

 

[Spimothy Leary]

127 and 140 ?
run those number again, preferably twice, and if you have access to it, try a different gauge, one is low but acceptably low, but the 2nd is high.

 

[ddanster]

I did it twice and came up with the same numbers. I also used it on my two 97 seadoo gs and got 131 for bth cylinders on one. The other i got 135 psi on both cylinders.

 

[SabrToothSqrl]

I actually think it's within spec, it's not ideal, but I'd keep driving it. Are the carbs clean? Replaced any grey fuel lines? new fuel filter? Correct oil used?

Still curious as to the OEM hours on it, if it's the original engine.

 

[Spimothy Leary]

I did it twice and came up with the same numbers. I also used it on my two 97 seadoo gs and got 131 for bth cylinders on one. The other i got 135 psi on both cylinders.

hmm, it could be argued that both of the GS models are ready for a top end as well, those should be 150.

 

[ddanster]

I'm also not the original owner so i don't know its maintenance history. Guy that sold it to me said compression was 145...evidently that wasn't the case! I originally used a compression gauge from harbor freight but never got higher then 90 psi on all my skies. I got a 30 dollar one from oriellys auto and it seems fairl.y accurate. I dont know the hours but the gs run well...the gtx is always a problem. That stupid bendix gear went out on me as well..fixed it though.

 

[Robj]

If it was my ski, I would just get it rebuilt during the winter. Now if it was summer I would run it and get it rebuilt over winter. For me, I want my skis trouble free for the three months that I actually get to use them. Spending a little cash during the off season is well worth it if I get to play trouble free during the summer. Also some of the rebuilders are offering some pretty good deals right now.

 

[Dr Honda]

Sorry... I was thinking an 800.

You have a 951... and 127 is on the acceptable side. and 140 is actually a little high. 135 psi is spec.

On the smaller seadoo engines... 150 is spec.

 

[ddanster]

Cool...thanks everyone for the info

 

[ddanster]

Yes has correct oil but does have gray fuel lines....fuel filter could use an eye as well.

 

[Spimothy Leary]

replace fuel lines, pull carbs and inspect clean and rebuild if necessary,

 

[SabrToothSqrl]

And shake it all about...

 

[bell99man]

If it ain't running right and you still have gray. Dude, replace that crap, clean the carbs and you will love that thing afterwards, I promise!

 

[Spimothy Leary]

that needs to be done first before you even think about the top end.

 

[ddanster]

that needs to be done first before you even think about the top end.

Ok thanks...ill give that a shot first before a rebuild.