Need Help, 440ex Motor Noise

[440exRider187]

I keep hearing a noise and it sounds like its comming from the engine. Its when the motors has a lot of stress. Like when i was stuck n sand and i was given it gas. Its perdy loud and it sounds like metal hitting metal, hard. Please help.

[lpmaster]

may be detonation try running some better gas or maybe an octane booster will work since you only experience it uner a heavy load

[440exRider187]

I Only Run 100 Oc

[lpmaster]

does it sound like lugging? chain slop? maybe a loose motor mount?nwhat compression piston you running?

[440exRider187]

I was thinkin mayb loose timing chain. Not sure on compression, i jus got like a month ago

[lpmaster]

100 octane fuel should be good enough if you you got an 11.5:1 or lower piston any higher would need better fuel. still sounds like detonation to me though. let us know what you find out

[440exRider187]

aight, thanx 4 tha help. ill let u kno what i find out

[Ruby Soho]

check your head gasket for leaks

[440exRider187]

it does have a small leak at the very top of the head

[drew416ex]

Mine started making lots of noise under load when my headstud pulled out. It started leaking between the head and jug

[Got Boost]

sounds like the head gasket, and 100 octane is more than enough for a any comp piston you can get in a 440, even 12.5:1 that is plenty.

[lpmaster]

depending on your elevation, jetting and ACTUAL compression ratio different octanes mya be required but an air cooled engine with a dynamic ratio of 12:1 would need more than 100 octane. most pistons for our "400ex" are build around the xr400 cylinder and head design which yields a slightly lower compression in our 400 motors. cam overlap also plays a role in dynamic compression. a more aggressive cam usually means more overlap which means slightly lowered compression. so while one 11:1 motor may need race gas the other may not