airmobile101
Active Members
Guys, Im not a 2-stroke guy and I don't know **** about them. Long story short. My neighbor down the street races this 2004 KTM 105SX in the Missouri Harescramble series. He recently acquired this bike by trading his CR85 for it. It was in bad shape when he got it,but he wanted a KTM. Anyways, the guy he got it from claimed it has a new top end. It very well may have,but it didn't last long. 10 hours tops! After sinking 500 bucks into it, we made it into a nice little bike.
Yesterday we ran into trouble. He was riding it in the woods behind my house and it just dies and wont start. He kicks it over a few times and claims he feels zero compression. I kick it over and claim the samething. So I slap a compression gage on it and we only get 5 psi total out of 10 kicks with the throttle being WOT. And the fun begins...........
I rip off the cylinder and find it looking like this. The ring collapsed and the top of the piston looks like it has collected aluminum or whatever on top of this piston. Its gouged good on top also. The cylinder has one extreme tiny score mark near the intake port. Sooo......... after making a few calls, a local dealer actually had a piston for cheap so we went and picked it up. Cleaned the cylinder with a scotch bright pad(didn't have a hone that size) and slapped it together. Did a compression check before firing and we achieved 160psi. Fired it up and she runs great. But....... Im a little concerned on how he is doing his pre-mix. He takes a 1 liter of Motorex and dumps it into a 5 gallon jug of fuel and runs it like that ??? WTF???? Isn't suppose to be mixed 40:1 0r 30:1 PER GALLON????? And yea.......... its like a disco smoke machine!!!!! lol
Anyways, here is a pic of the old and new piston. Give your thoughts on the piston and pre-mix. I would have ordered a hone,but we are on a time crunch since he has a race this weekend.
http://www.offtopic.forum/uploads/imported/2012/05/IMAG1055-1.jpg
Yesterday we ran into trouble. He was riding it in the woods behind my house and it just dies and wont start. He kicks it over a few times and claims he feels zero compression. I kick it over and claim the samething. So I slap a compression gage on it and we only get 5 psi total out of 10 kicks with the throttle being WOT. And the fun begins...........
I rip off the cylinder and find it looking like this. The ring collapsed and the top of the piston looks like it has collected aluminum or whatever on top of this piston. Its gouged good on top also. The cylinder has one extreme tiny score mark near the intake port. Sooo......... after making a few calls, a local dealer actually had a piston for cheap so we went and picked it up. Cleaned the cylinder with a scotch bright pad(didn't have a hone that size) and slapped it together. Did a compression check before firing and we achieved 160psi. Fired it up and she runs great. But....... Im a little concerned on how he is doing his pre-mix. He takes a 1 liter of Motorex and dumps it into a 5 gallon jug of fuel and runs it like that ??? WTF???? Isn't suppose to be mixed 40:1 0r 30:1 PER GALLON????? And yea.......... its like a disco smoke machine!!!!! lol
Anyways, here is a pic of the old and new piston. Give your thoughts on the piston and pre-mix. I would have ordered a hone,but we are on a time crunch since he has a race this weekend.
http://www.offtopic.forum/uploads/imported/2012/05/IMAG1055-1.jpg
