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View Full Version : blew the top end again on my 86r...


dirtbike77
09-07-2003, 08:30 PM
lately the bike have beeen actin kinda wierd when i first crank her up and ride for a while she would be alright... but then out of no where she would start spuutering and poppin and backfiring.. then when i go and try to kick it, it would kick back... and backfire..tried changing the plugs and the same thing?

so i took it apart today and noticed a poddle of coolant on top of the piston? also on the front part of the piston which faces the exhaust port, right under the top ring a section of the piston is misssing? what could of caused this..
YTZ250#1
09-07-2003, 10:13 PM
sounds like you were runing it to lean and it got hot,real hot.
dirtbike77
09-08-2003, 07:00 AM
i have a 150 main jet in it and have the jet needle at the the third groove from the top?

br9eg plug in it?
YTZ250#1
09-08-2003, 07:22 AM
Do yopu have any motor mods?(porting or biger bore)My R has a 168 mainjet but has both mods listed above,it is a 265 now wiyh a aftermarket
head.
CHAINSAW
09-08-2003, 02:09 PM
How long was it together? If the person who did your bore job last did a poor job of cleaning up your ports, he owes you a new top end. (the sharp edge on the port will rub against your piston on the down stroke and do that to your piston)
Just one suggestion if it wasnt that long ago. As of right now, Im guessing you have very low compression.. looks like another bore job to me, along with a new piston. The puddle of coolent was probably from you, when you took the head off... Its hard to keep that from happening. Either that, or a bad head gasket.
dirtbike77
09-08-2003, 08:27 PM
fmf pipe' silencer
bored .60 over
150 main jet
boyessen reeds
shaved head
200x Basket
09-08-2003, 10:53 PM
ok, the outside of all the ports should have been sanded/grinded at a small angle to prevent that. if the bore is good, sand the edges and buy a new piston / rings and install. then kick the person who bored the cylinder in the trailprotrailprotrailprotrailprotrailpro. go to www.mcdizzy.com for some "real" 2 stroke advice.
atc86r
09-08-2003, 11:10 PM
I saw that last year at silver lake on a MacDizzy engine. honda310r's. The same little piece of the piston was stuck on the head. His piston was new by some standards. He said he had some detonation a run or two earlier when dialing it in then it blew.
CHAINSAW
09-09-2003, 06:59 PM
lol so much for some "real" 2 stoke advice.. lol