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Discussion Starter #1
hello everyone, newbe here

i have a 1980 xl250s that i recently put a ney piston and rings in.
the piston was a pop top piston and now it spark knocks bad.
is there anything i can change on the firing to help it and if so can you tell me how.


thanks
 

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Did you change the compression? How is the timing set on that bike?

Welcome.
 

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yes the compression did change and the timming is set to factory , this all new to me. if it were a briggs it would be no prob, but a little different for me
 

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yes the compression did change and the timming is set to factory , this all new to me. if it were a briggs it would be no prob, but a little different for me
then retard the timing by a bit. no idea by how much you'd need to do that, so just do a bit at a time until it goes away.
 

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then retard the timing by a bit. no idea by how much you'd need to do that, so just do a bit at a time until it goes away.
:plus1:

That's really your only option.....since there is no way now to drop the compression back down. The fact that hi-octane fuel helps pretty much proves this. In some parts of the country, hi-octane racing fuel is available.....if you search hard enough. IIRC, it runs about 105-110.

Long shot:
Put in a colder plug.
 
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