high compression rebuild died after 3 weeks help!!

[hardcoreracer87]

ive got a problem im 23 my brother is 15 we both have predator 500s, my step dad got my brothers predator 500 rebuilt about 2 or 3 weeks ago they put a 12.5 high compression piston in it and shaved the head .002 and did a 5 angle valve job on it he has ran 3-4 tanks of gas threw it and tonight it locked up on him i went over there and checked it out im pretty sure the rod snapped my step dad is acting like its all my little brothers fault but they kept factory rod in it. what kind of compression can a factory connecting rod take? trying to prove my brother innocent step dad says it broke cause he was over revving it

[Bruce!]

Welcome to the board!

[hardcoreracer87]

thanks

[joshr08]

aftermarket cdi? who rebuilt it? (dont really need there name but was it someone that knows the fuji motor?) if the timing is off even just 1 tooth on either cam you can bent then snap a valve off and that will lock the motor up too. has the motor been pulled back apart to know it was the rod for sure? stock rod is good to about 10k rpms stock cdi is set at 8500rpms or 8700rpms IIRC.

i ran my stock predator motor last year right on the limiter on the 1/2 mile track i run with no problems and its set at 9700rpms. no problems with my motor.

[hardcoreracer87]

its the stock cdi titan motor works rebuilt it hes pretty knowledgeable about polaris, we've haven't taken it back to him yet it just happen last nite, i looked at it drained the oil to check for any metal shavings didn't find any i put it in gear and rolled it backwards and the motor rolled back but it didn't turn over the full rotation after it stopped i rolled it back forward and it stopped about the same spot like the rod was getting wedged, that's why i figured the rod was broke , after the rebuild i noticed when you shut it off the bottom end always sounded like it stopped hard kinda a loud clunk sound but step father said it was cause the high compression

[joshr08]

you have a busted valve.
and its not letting the motor go past the busted valve to get to TDC and back down. start looking for a head. would be my guess that really sucks did they install new OEM valves or aftermarket? knowing polaris and knowing the fuji motor are 2 totally different things. good luck and please keep us posted on the findings.

[hardcoreracer87]

all right that does make sense didnt even think of it being a valve since they had a valve job done ill deff let you know what we find out when he tears it down

[joshr08]

only reason i say valve is every time i have seen a predator bust a crank it usually goes right out the bottom of the cases. and with it having a stock cdi it cant be over revved.

[Predasaurs]

Originally Posted by hardcoreracer87

ive got a problem im 23 my brother is 15 we both have predator 500s, my step dad got my brothers predator 500 rebuilt about 2 or 3 weeks ago they put a 12.5 high compression piston in it and shaved the head .002 and did a 5 angle valve job on it he has ran 3-4 tanks of gas threw it and tonight it locked up on him i went over there and checked it out im pretty sure the rod snapped my step dad is acting like its all my little brothers fault but they kept factory rod in it. what kind of compression can a factory connecting rod take? trying to prove my brother innocent step dad says it broke cause he was over revving it

was it a brand new factory rod and bearing?

[hardcoreracer87]

Think they kept the factory rod but put new bearings