1996 GTX- Do you rebuild both cylinders? Poor compression in PTO cylinder

[Big Fish]

I have a 1996 GTX that is hard to start, doesnt idle very well and gets a top speed of 42MPH but it does run. I have never replaced the old TEMPO lines nor rebuilt to carbs so I have the rebuild kits, needles and seats and all the fuel line. I plan on doing the carb rebuild and replacement of fuel lines this week. Before I do this I compression tested the ski and found 150 in the front cylinder and 110 in the back. I only have $30 tester but I cant imagine it would make that much of a difference. So here's the question. After I rebuild the carbs and change out the gas lines if I still have this pressure difference and poor performance I assume I need an engine rebuild. I've read a bit about cylinder rebuilds but can you just rebuild one and keep the other stock?

 

[soccerdad]

You could, but I would not. 110 seems like it may have eaten a piston from being too lean (fuel lines). I would pull the cylinders and really inspect stuff. You may find that you have to bore the bad one. If so, you really need to do both. At the least I would pull both, and hone and replace the rings if the pistons look cherry.

 

[Big Fish]

Soccerdad, thanks for the quick response. So another dumb question, I need to rebuild the carbs and change the fuel lines so I'll do that. However if I pull the cylinder head cover to inspect the pistons will I need a gasket kit to put it back on if I decide not to rebuild at this time?

 

[330xi]

Soccerdad, thanks for the quick response. So another dumb question, I need to rebuild the carbs and change the fuel lines so I'll do that. However if I pull the cylinder head cover to inspect the pistons will I need a gasket kit to put it back on if I decide not to rebuild at this time?

I would at the very least. I made the mistake of taking the head off, but not replacing the gaskets on my sled (2005 SkiDoo 600), and it was leaking antifreeze into the cylinder.

 

[racerxxx]

BRAKES ON HARD!!!!!!!!!!! Just pull the rear rave valve housing--2 screws. It's like a factory inspection window. Get a nice bright flash light and you can see right into the cylinder and also the exhaust side of the piston, just rotate the PTO and inspect. Do not pull the head until you have to.

 

[Coastiejoe]

Yep yep. And the fuel line replacement is a must do. The longer you wait the higher the odds if serious and non-repairable damage.


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[Big Fish]

Racerxxx & Coastiejoe - Thanks. Pulling the rave valve makes sense to inspect the cylinder. Will I need a gasket to put that back on after I pull it? I finished changing out all the fuel lines so thats done. I'm currently working on rebuilding the carbs and ran into a slight problem. When I tried to take one of the phillips screws out of the internal part of the carb the screw was in there hard and it stripped. I'm contiplating just not changing that gasket in there as I'm not sure what to do otherwise. I guess I could bring it to a shop down the street to see if they can tap out that screw but I'm leaning toward just leaving it. Any thoughts?

 

[racerxxx]

I'd use a new gasket, but if the cylinder is scored up you're beyond a gasket.

Those internal screws, use an impact driver CAREFULLY make sure you're squarely sitting ONLY on the aluminum housing of the carb and not on ANY important parts that can break off.

 

[racerxxx]

Worst case you can drill the head off the screw and remove the plate then the screws USUALLY come out with your fingers or pliers. It's the surface area of the countersink on the screw that holds them so darn tight and any amount of corrosion between the two surfaces makes it that much harder to break free. I've done this several times before, only drill it if you feel confident in doing so, one slip and you can ruin your carb.

 

[Big Fish]

Racerxxx, thanks. Problem is that screw is stripped now so I'm not sure what to do at this point. Again, I"m leaning toward just leaving it and not changing out that one gasket and what looks like a small plastic flap held in by a screw.

 

[Big Fish]

Racerxxx- I am absolutely not confident in drilling so I'm either going to leave it or bring it somewhere to have them drill it out. I'll probably leave it.

 

[reclipse93]

those screws drill out very easy, if you nick that kidney block its ok, but by all means don't be a butcher.

 

[Big Fish]

Ok guys. I left that screw alone and just finished the rebuild without that part on the Mag carb. Everything else went very smoothly and I tested the skinout of the water and it ran great. I trsyed several times and set the RPMs at idle to 3000 out of the water as the manual said. I got it to the water yesterday and it started and made one pass OK then stalled at the dock and I havent been abke to start since. So frustrating. It started perfect and ran on the trailer but now in the water and im dead. Wanted to use it a bit this weekend but cant get it started. Changed out the plugs made sure they were gapped right and still nothing. It seems im getting gas but im not 100 percent sure. Is there a way to test that gas is getting to both carbs?

 

[- BiRkS_]

Did you replace all the lines and inspect the fuel selector valve? Normally most of us just replace the valve for the 30$ insurance. Another place to check is the fuel/water separator filter-sometimes the o-ring gets munched and you get an air leak. And whenever i do a fuel system, I install an inline paper filter right before the carbs to catch anything before ruining a carb job and its an inspection port to see if you're getting any air bubbles, bad gas, water, or debris in your fuel.

If the ski stalled and you suspect fuel, First thing is loosen the gas cap and listen for a hiss. (possibly your vent line is pinched and creating a vaccum) if that doesn't work, do a visual once over the system for any leaks or pinched lines. Check the pulse line at the carb for a leak or if it popped off. you can pull the return line off the pto carb, crank the ski and see if fuel is making it through the carbs. (be sure to disable ignition system when doing this)

And just as an FYI. Go back to Racerxxx's first post. Inspect the rear cylinder first. Right now you're running in circles and may be ignoring a big problem if left untouched. IMO i would have investigated the compression issue first before wasting new carb gaskets because now you might have to take the carbs back off and tear apart the engine...just my 2 cents

 

[Big Fish]

Birks, thanks. I did not clean nor inspect the fuel selector although I wa ted to. Couldnt figure out how to do it. I also didnt do the inline filter before the carbs but that sounds like a good idea. I did change alm the gas lines but not the vent lines. I dont think they are pinched but I will take a look tomorrow to double check. Thanks again for the help.