You can run a four stoke really lean and not burn a hole in a piston. You have to spray it with nitrous with no extra fuel to actually burn a hole through a piston. A buddy of mine runs 2 strokes though and said they are different. He said you can burn a hole through a piston from a very lean condition and it doesn't take long. I think you should mix the oil and gas to the proper mixture and read the plugs. If it's lean then adjust the fuel mixture screw on the carb until it's right.

 

I am having a similar issue with my 400. I am on piston #2 and after about 15 min it died. The plug was almost silver. I had already bypassed the oil injection pump and just use pre-mix at 40-1. It runs great but like above it will burn up a piston before the temp light will come on. Mine is .040 over, piped, DG silencer, V-force reeds, a 260 main jet, clutch kit, and a fresh rebuild. I had the head and cylinder decked and the machine shop only took a total of .005 off, but they are 100% true with a new OEM head and base gasket. It also has new crank seals. If anyone has any ideas I would love to hear them this getting expensive. Thanks ahead.

 

There are lots of little things that can screw up a 2-stroke. Cracked fuel lines can suck air and make it run lean too.

 

remove primary clutch, start engine,while it is at idle spray the pto seal with carb cleaner, starting fluid, or anything that sprays and is flammable. if the idle changes or dies you have a seal leaking. repeat with recoil side, after starting, pull rope slowly just enough to open hole where rope goes into housing. spray into rope hole for about 4 seconds and allow to idle for 20 seconds, again if idle changes you have a leaking seal. don't worry it won't blow up in your face. there aren't any sparks inside of housing only magnetism.

this is the easiest and fastest way to check seal leakage on a 2 stroke

 

i may be interested in buying it as is. PM me if you're interested

 

Just tossing this out there, but if you are running the wrong spark plug, such as one that's too long or too hot, this also could burn a hole in your piston. Is the hole by any chance in the very center of the top of the piston?

 

Before you rip it apart following contentsunderpressur advice(which is good advice) I'd get a can of carb clean or starting fluid on hand, once you start the motor you can spray the cases while idling and if you have a vacuum it will suck in the fluid and cause it to high idle showing you where the leak is. This isn't a fool proof method but it does usually work, its a old school mechanics trick. 2 strokes don't just start to burn pistons out of the blue because of lean burn conditions unless its a vacuum leak, if it was jetted and running decent and started burning pistons and you've "cleaned" the carb after the first time- I would find it hard to believe it a carb problem unless one of the boots are cracked which you say arent so I'd look to seals with a can of starting or carb fluid. Let us know how you make out please.

 

Does anyone think the pipe may be my problem. I still have the stock pipe. That is all I can think of to be my problem. Maybe I am not getting enough back pressure and it is leaning out. Any suggestions would be great. Thanks

 

Edit - Sorry, just re-read what you said and my input was useless. Ooops