high compression rebuild died after 3 weeks help!!

[Predasaurs]

Originally Posted by hardcoreracer87

Think they kept the factory rod but put new bearings

ok was just wondering i did the exact same rebuild but put in a new rod i was gonna use a falicon but the stock one was good because i wasnt going over 10k rpms , im taking the first ride today breaking it in see how it goes

also what fuel u run?

[hardcoreracer87]

It ran like a stripped a** ape till it locked up we r running about 1 gallon 110 octane 3 gallon 93 mix in it

[joshr08]

93 is all you need with the 12.5 piston

[hardcoreracer87]

well the guy that built it took it apart and it bent two valves and trashed the head and he say it was my brothers fault cause he over revved it....idk it got the factory cdi box. if anybodys got a head they would let go let me know

[Predasaurs]

Originally Posted by hardcoreracer87

well the guy that built it took it apart and it bent two valves and trashed the head and he say it was my brothers fault cause he over revved it....idk it got the factory cdi box. if anybodys got a head they would let go let me know

ofc hes gonna say that he doesnt want it to be his fault then have to fix it 4 free

i had my head shaved and i had to run 2 head gaskets

he should have checked the clearances better

and it has a cdi u can hold it pinned and shouldnt go and faster ,

when i was looking for a head i looked on ebay i think they were 500ish

best a luck

[joshr08]

it wasnt your brothers fault if the valves hit the piston it was out of time....plain and simple. engine builders fault. where you located?

[joshr08]

pm sent

[ridemhard]

check to see if the cams are still good. they tend to break, so polaris cams have a breaking cam so it shouldnt do that much damage to the engine. with the top end apart, hand spin the engine and see where the cam lobes/valves are located at TDC. the cams may look ok but they may be broke. good luck

[joshr08]

predator cams break??? thats a first i have ever heard that in all the millions of pages of motor threads on the fuji motor. the head its self is junk not the cams and theres no rolling the motor over as the valves bent and jammed into the head and wont let the piston even get to TDC. I know this because we have been talking. anyways back to the cams breaking i would really like to read about this problem as i have never heard about it.

[ridemhard]

not saying all cams break, but if something does go wrong, there is a feature that cracks in the cam letting the lobes and teeth spin sepreatly(but not freely). it may bend the valves but save the head and the piston. like i said, it may work under certain conditions. This happened to me, it took us forever to figure out what was wrong, the engine would turn but not all the way and lock up only at one point. took off the top and saw the timing chain was almost skipping, realizing the lobes were pointing in the wrong direction. just saying that may be the case and something to look into before getting to involved