98 yz 250 knocking and pinging no top end

May 7, 2007
9
0
I got the bike out in spring and went trail riding at the end of the ride we heard a knock at idle figured it was piston slap so we put new piston and rings in and found the noise was still there mainly at idle when the bike is warm. We tore the whole thing down and thought maybe crank bearing but everything checked out ok once again assembled it and went out to ride and it started spewing antifreeze from the over flow so i went to a shop by where i was riding and they resurfaced the head and put it back togethor. went back to the wood and rode for a while and the bike is pinging and has no top end. and is getting real hot and spewing antifreeze once and a while. please help with any info
thanks
 

kx125412

Member
Mar 30, 2006
341
0
You're bike is jetted to lean. Find out what the stock jets are for your bike and then find out what's in yours. Start with stock jets and lean out as need be. It wouldn't hurt to bump up to some higher octane fuel either. I just run marine gas in mine and it's ok but it depends on altitude and temperature.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
Master of Faster said:
I got the bike out in spring and went trail riding at the end of the ride we heard a knock at idle figured it was piston slap so we put new piston and rings in and found the noise was still there mainly at idle when the bike is warm

If it's knocking at idle it's not jetting, or detonation or anything to do with combustion. There isn't enough of a load on the engine at idle to cause these types of problems. You have something mechanical that is vibrating, or a worn part that is rattling around.
 
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