Wierd knocking noise when cold PLEASE HELP

[440EXRACER#10]

I have a 2002 Honda 400ex. It has everything done to it. 440 big bore, 12:1 high comp piston, stage 3 hotcams, full curtis sparks exhaust, custom cdi box, aluminum air box, air filter,trx 450r carb, trx 450r snorkel, trx 450r throttle, everything. It was professionally rebuilt about 20 hours ago and it is insane fast. But, when it is cold it has a wierd knocking noise everyonce in awhile. It'll come and go while it's idling. But once I hop on it and take it easy down the road to my trails, and it gets hot the knocking goes away and it is as quite as can be engine noise wise. The valves are perfect in speck and I don't know what to do to fix it. Please let me know. Thanks

[#484]

Was the timing chain replaced when it was rebuilt? That's a very common noise on the 400. Is the noise coming from the right side of the engine, if so check the chain and tensioner

[01boneless]

a TICKING is normal on most ex's. a knocking is not, get a stethoscope and pin point where its coming from bottom end or top end.

[Stickman400]

You're running race fuel right? If you're running 93 in that setup it could be pining from too low octane fuel. Atleast I think it's pinging, it could be the other thing, I can't remember, someone help me out.:confused:

[01boneless]

Originally posted by Stickman400
You're running race fuel right? If you're running 93 in that setup it could be pining from too low octane fuel. Atleast I think it's pinging, it could be the other thing, I can't remember, someone help me out.:confused:
denotation? good call stickman i totally missed the 12:1 compression, u need 100+ to run that.

[2001400exrida]

i'm running 12:5:1 with pump gas. i was always told that 13:1 is the breaking point for needing race fuel.

[chronicsmoke]

Originally posted by 2001400exrida
i'm running 12:5:1 with pump gas. i was always told that 13:1 is the breaking point for needing race fuel.

Big difference in liquid cooled vs. air cooled..

A 400ex on 12.5:1 would need race gas unless it was dyno tuned to perfection

[2001400exrida]

ok i see. well the 426 runs 93 octane with 11:1, and i've never had a pinging problem so i know that 11:1 would be safe. I suppose you would need 100 octane for 12:1 if it is in fact different than the liquid cooled machines.

[440EXRACER#10]

But remember. Like I said, it only does it when cold.

[dxcody]

Def wouldnt be pre det because it wouldnt quit when it was hot.

It would do it when it was hot.

Mine did that sometimes when it was cold, but it was more in the top end, like by the valves. It made me think it was a rocker arm sticking or something. Idk i never worried about it... Then a week later i dropped a valve.

[ride red 14]

Could possibly be a floating valve. If it closes a little late the piston could be smacking it. What kind of valve springs?