Posts
699
Joined
3/30/2015
Location
San Diego, CA
US
hey guys, 2009 yz 250 put a fresh top end and apex head with the mx dome in, for pump gas and adjusted squish band. put about 50hrs on it and the head gasket blew, figured that was about normal considering the hours on the top end. put another fresh top end in and got about12-15 hours on it before i noticed low coolant and head gasket blew again in the same spot. this seems premature to me. Should i be concerned? seems a little suspicious to me as ive never had issues like this with the previous 2 yz's ive had. i did notice a little bit of pinging on a hot day at pala not sure if it was blown and that caused the pinging, or it got hot cause of low coolant and was pinging cause of that.
Plug looks lean…. Maybe little,richer on jetting and/ or splash of C12
i noticed the plug looked lean too. ive ran the same jetting since getting the bike dialed in when i first got it. i do run a 50;50 mix of premium and 100octane. im guessing it looks lean cause of running it with low coolant but i will definitely keep an eye on it and maybe fatten it up some.
Check head & cylinder top for warpage…inspect water pump impeller & drive gear….you got very hot to melt that oring… mag side seal for air leak….
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