1994 GTX Hole in Piston

[Thorgtx]

Hi all, great forum! I just purchased a 1994 GTX (maybe its a '93 as it was made in 2/'93 but it is a 650cc which I don't think they made in '93 (I don't have the registration card yet to confirm)). The previous ower said it had no compression and they were right. The front cylinder has a hole in the center of the top about 1/2" in diameter.

What would have caused this?

What else could have been damaged when this happened?

What would be the easiest/cheapest fix without skimping too much?

What should I do find/fix the root of the problem and keep it from happening again.

Thanks,
Brett

 

[Thorgtx]

Here is how I plan to proceed with my "Piston Hole" problem.

1 Remove the front jug and offending piston.
2 Inspect the crank, if it looks ok and not rusty, I will leave it alone.
3 If the cylinder is not scored then I will hone it and leave it alone.
4 Replace the cylinder.
5 Leave the other cylinder alone (or should I pull it apart and change the rings?)
6 Drain all fuel out and inspect (maybe replace fuel lines)
7 Clean the fuel petcock. Replace fuel filter.
8 Drain all injector oil out (without introducing air into the line) and refill with new oil.
9 Inspect/replace oil injection lines (there is alot of oil in bilge, maybe a line cracked?)
10 Clean the carbs.
11 When restarting, run 40:1 premix along with the oil injection system for the first tank of fuel. Monitor the injector oil usage (Is there a better test?)

Does this sound like a reasonalble plan?

Thanks,
Brett

 

[RX951]

Both cylinders are together. there is no front jug. You need to find the source of the problem. It sounds like it got starved on fuel and leaned out, got hot and burned a hole in the piston. whats typical of this scenario is when the motor begins to run lean form fuel starvation [plugged inlet filters], carbon will build up on top of the piston. then, the carbon will get hot form the combustion process and eventually, if the fuel starvation problem is not fixed, the piston will get a hole melted in the center. If you ever look at a 2 stroke piston thats good, upon dissasembly, look at the bottom, there will be a dark spot. the most head on a piston will be in the center. Well, in a nutshell, you need to make sure that no aluminum fragments are in the case of the crankshaft area also. also make sure the cylinder walls are not scored, rering the other piston, and most important, go through those 14 year old carbs. and replace all gaskets. I would also consider going premix.

.02