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Discussion Starter #1
The sled had a fried piston so I put a new cylinder and top end on it cleaned evrything and put it together fired right up after the 4 th pull went to break it in alittle bit and I went to give it some speed and it started to big out at about 25mph and wouldn’t have any more power. Looking for some ideas to look through. And when I pulled the plugs it’s running very lean. The spark plug tips are white. Just wanted make sure evrything is good cuz I don’t want to have another piston fry on it
 

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Why did it fry a piston?
If your plugs are white it did it again!
You have to find out why!
Are the carb pilot passages pluged up?
Do the seals leak?
 

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Discussion Starter #3
Welcome
Why did it fry a piston?
If your plugs are white it did it again!
You have to find out why!
Are the carb pilot passages pluged up?
Do the seals leak?
We found installation in the carbs and engine when we opened it up so we cleaned out evrything and put it back togther so we assumed the installation plugged it up causing the piston to fry
 

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Discussion Starter #4
We found installation in the carbs and engine when we opened it up so we cleaned out evrything and put it back togther so we assumed the installation plugged it up causing the piston to fry
Also we put all new seals on and evrything I didn’t see any seepage coming out the sides when I looked
 

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Silly question you did get the pistons in the right direction?
What is your compression now?
 

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Discussion Starter #6
Silly question you did get the pistons in the right direction?
What is your compression now?
I put the arrows facing the exhaust and when I compression tested it it hit 110 on the first pull and on the second it went to 120
 

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I'd lean (no pun intended) toward an air leak, probably base gasket. It might of slipped out just enough to look normal, but has enough of an air leak that when pressure builds up (going faster) it leaks more.
 
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