Hole in my piston

[ivanb1]

When i tested my new exhaust (toomey) my piston get f*** up. i was going 6 gear because i wanted to see how fast can goes my blaster with the new toomey. Then engine turn off. i dont know why , but i could not start up again. when i went with my mechanical, he opened the engine and we saw the piston lined.
he still not give me the blaster, so i dont know why this happened

someone know why this happened?.

sorry for my bad english, i hope you can understand me.

 

[sheeblast]

my guess, you didn't rejet it for the exhaust and burnt the hole from running it way to lean.

 

[bonzaiking]

my guess, you didn't rejet it for the exhaust and burnt the hole from running it way to lean.

yes i think your right

 

[1bad442]

yep i agree with shee also. a toomey definately needs to be rejetted over a stock pipe

 

[brandoz28]

not a cheap mistake, but i bet you remember to jet it this time......

 

[phragle]

Before making any change to the blaster, you really need to know
1. Why do I want to change it.
2. what will change it.
3.how it changes it
4. what else does that change effect.

In you case, you added an aftermarket exhaust which does a few things..
a. weight savings
b. moves the power target area of the motor
c. effects airflow
d. alters scavanging and air fuel ratio
etc.

An after market pipe, when the engine is tuned/jetted/ ported to match increases the power. It will not increase the top speed (may SLIGHTLY is more RPM are allowed). Higher top speed is achieved with a gearing change, since you will have more power to pull taller gearing. A pipe makes a significant difference in the total airflow of the motor, thus will alter the air/fuel ration requiring rejetting. A hole burnt into a piston signifies an incredibly lean condition generating a piston temp in excess of 1400 degrees F. Either you were previously right on the edge, or you also have an airleak to run that lean.

 

[Blaster200boy]

Phragle said it correct. I was just about to post the same thing, but I then read his post. A Toomey should be jetted around a 330 main with stock airbox and stock carburetor. Dont take my word for it though because Altitude and temperature will change jetting too. I'd start really high at like a 350 and do a plug chop. If it is black, it is rich, if it is grey or white, it is most likely lean, if its a cardboard/brown color, its jetted perfect. I recommend checking to see if the rod is ok. It can 1mm play side to side, but absolutely none up and down play. Then check to see if the cylinder has any scarring. If so, see what size piston you had when it blew up, go the next size up on that piston and make sure when you replace it all that you use all brand new gaskets. The best base cylinder gasket ive found that works best is stock. Thats your choice though. Then its good to invest in "Holeshots" leak down tester. It will tell you if you are leaking any air into the cylinder. Once you have done that all, make sure your jetting all good, break it in, and you should be ready to go!!!