compression ?

[Cornnutt]

I recently got a 97 GTX from a buddy of mine who owed me money. He said it ran, but not great. After finding this site I changed all grey fuel lines, cleaned fuel selector valve, filter, rave valves, and carbs. Fuel system was pretty clogged and RAVE was terrible. Thought that would probably fix it. When I was putting it all back together I checked the compression. It was 140 on the mag side and only 100 on the pto side. I checked it with the carbs off and a good batt with the plug wires grounded. I removed the head and the side with the low compression has a small vertical groove in the bore I can feel with my finger. What is the best way to fix this? Can I re-sleave the bad cylinder? I think the best solution would be to pull both cylidners have them bored and get new pistons, but thats probably more money than I have to spend right now. Is it possible since the one side is good to just fix the problem side? I have rebuild 2 stoke motorcycle/snowmobile top ends before so I could do the work myself, but I think just the parts are going to be pretty expensive.

Thanks in advance this site is great.

 

[seadooya]

bore the bad cylinder, and get new piston. Only problem, you'll need to remove the good cylinder and replace the base gasket, since it'll rip apart taking the bad cylinder off

 

[Cornnutt]

Both cylinders dont need to be the same bore?

 

[seadooya]

your going.... 0.010 diameter in bore, you'll be alright. You could send the cylinders to Fullbore, get both done and pistons/gaskets for 300 buks. Thats probably the safe/reliable route.

If you go that route, i'll buy the "good" piston

 

[Cornnutt]

I was just looking @ there site. I would have guessed it would have cost double to get all that work done. I am in the process of tearing everything out right now. I will send both cylinders into them. Which ones are the good pistons Wiseco? Is there anything else I should look for while it's all tore down? I did start it with the garden hose hooked up just to make sure it ran. It idled fine, but water was leaking out of the thing that looks like a 3rd rave valve on exhaust. not spraying just dripping. Is that normal?

Does anyone have any idea on what turnaround time is like with full bore?

Thanks for all the help.

 

[seadooya]

5-7 business days for top-end, through them. Go through there website and not ebay, and you'll get free shipping.

Is the water regulator leaking or is it the "flange" that its threaded onto?

Still interested in the good piston...

go with WSM pistons, either the regular ones or the platinum ones, but those will cost more.

 

[Cornnutt]

I went with the platinum top end kit with rave valve mod. Does that come with the good pistons? I have it all tore down. The bad cylinder had a caged bearing so I think it was replaced before. The 140psi cylinder still had the cage less bearings. Could it have that good of compression with never being replaced? Looks like whoever rebuilt it before left the good cylinder on and cut the new gasket. The bad cylinder didn't look terrible to me. I am sending the pistons with the cylinders Full bore will do a failure analysis. Is there anything I should do while I wait for my parts to come back?

 

[seadooya]

the plat. series, is WSM best piston. As for "diagnosis" to the pistons/cylinders, you need to look at the oil injection fitting to that cylinder and carb.

Still want the good piston upon return.

 

[Cornnutt]

The oil injection is unhooked running premix. I've read on here where most people prefer the injection, but I tested my pump and it didn't put out any flow. If it runs good after new cylinders next year I might buy a new pump. Just depends on how much of a pain premixing is fouling plugs, smoke etc. The previous owner unhooked the cable to the pump and mixed the fuel in the tank. I have ordered the block off kit. Should be here way before the cylinders get back. While I am waiting I will change the oil in the pump. Is there anything else I could do?

Seedooya do you want the old pistons? Both of them looked good to me, but I'm no expert. They were differnt the one that came out of the good cylinder had a hole in it on the side. It was put there on purpose not a burn through or anything. Is that how stock seadoo pistons are? If you want them and full bore sends them back you can have em.

 

[scooper77515]

pistons are probably good. Just the rings are shot.

Personally, (close this window NOW!!!), I would hone the faulty cylinder and run the crap out of it on existing rings.

OK guys, go ahead and ban me now...

But you all know I am cheap.

But honestly, you couldn't really hurt it and make it any worse, right?

That is assuming the groove isn't too bad, of course.

 

[seadooya]

The oil injection is unhooked running premix. I've read on here where most people prefer the injection, but I tested my pump and it didn't put out any flow. If it runs good after new cylinders next year I might buy a new pump. Just depends on how much of a pain premixing is fouling plugs, smoke etc. The previous owner unhooked the cable to the pump and mixed the fuel in the tank. I have ordered the block off kit. Should be here way before the cylinders get back. While I am waiting I will change the oil in the pump. Is there anything else I could do?

Seedooya do you want the old pistons? Both of them looked good to me, but I'm no expert. They were differnt the one that came out of the good cylinder had a hole in it on the side. It was put there on purpose not a burn through or anything. Is that how stock seadoo pistons are? If you want them and full bore sends them back you can have em.

i'm all over it, Cornnut....pm'm you. Dans' cool, he'll send them back. Take the time now, and forget the oil bottle, but go through the carbs, thats' probably the "root" cause.

 

[scooper77515]

What, Seadooya? No comment on my comment? I thought for sure that would wake everyone up.

Guess not

 

[Cornnutt]

The groove didn't feel to bad. No rough edges. Couldn't catch a fingernail on it, but it was bad enough to make compression way low. Your idea might have worked. I'm not sure how it could of happened. That side has been rebuilt before so maybe whoever did it did something incorrectly. The pistons both looked good to me. A little carbon built up on top and washed away where the ports are. We'll see what full bore comes up with. Hopefully they will be on their way soon.

Thanks for the idea.