[BackBreaka]

Hi All,

what would cause a piston to blow a hole in the top of it about the size of a dime?

and any ideas what other damage this process may have caused.

Thanks,

 

[RJ Gleason]

Lean.
Too little fuel or an air leak.

 

[kccats]

Yep! Bad fuel, too muck timing, or air leak.

 

[BackBreaka]

thanks......

 

[RSR Mechanic]

Easy fix, but you should try and get any debris out of the bottom of the engine. A shop vac with a smaller hose like new fuel line taped to the hose can do the trick, but be careful not to suck up flamable liquids if you use this process.

 

[Ohio Oil]

1980 el Tigre trying to get my friend's sled running. Similar problem here. Sled would not start, found dime size hole in the piston. Replaced the piston..I now have great compression and getting vacuum pulse to the fuel pump. I rebuilt the fuel pump as well. Also...drained the carbs and fuel tank, put fresh fuel in it. Problem...it still won't start. If I shoot just a little starting fluid in either cylinder it will run for a second.

My question is can weak spark create a lean condition and blow a hole in the piston?
I'm wondering if the starting fluid will light with weaker spark whereas the fuel won't?

I can see fuel in the lines going to the carbs, it's obvious to me the bowls are full and fuel is in the line.

 

[BC_Dan]

If the spark isn't igniting the fuel, you would have a rich condition instead of a lean conditon.

First thing I would do is pull and clean the carbs, making sure the pilot jets and any other jets are spotless. Also, check the inlet needle and seat and float height. You may have fuel in the lines, but the inlet may not be opening to allow the fuel into the float chamber. Lots of times, varnish will stick the inlet needle to the seat, simply removing it and cleaning usually clears that right up.

 

[Ohio Oil]

I'm an auto tech guy...never worked on these motors. What's up with the cables that attach to the carbs. One for the choke..the other for throttle. They're threaded with double nuts. What's the proceedure for disconnecting them so I can clean up the carbs?
Thanks