calling all engine gurus

[redrider311]

heres the syptoms


theres alot of carbon build up in my pipe ALOT of carbon..
and i read today that carbon is a cause of a knocking engine
and my engine knocks alot
soo i was wondering if this is my problem
and i need to know what i need to do..
isnt carbon cause from burning extra gas?
if so do i need to change my jetting

well your the geniouss here.. ill let you guys figure it out :p

[400EX QUADER]

You're prolly really rich on the jetting.Check ur spark plug and if it's black you're rich.

[rsimmons_82]

like he said, your pobably way rich on jetting. as far as the knocking, im not sure what your trying to say here. its probably just the valves that r rattleing, ive never heard a 400 that had quite valve train.

[crazyatvn]

Excess carbon can build up that will raise your compression and couls cause spark knock. But all depend on the knock. valve train should be quiet is all is good and adjusted right. Carbon is a cause a a rich carb you need to check your jetting and make adjustments.

IMO
so don't get pissed at me

[redrider311]

alright im VERY new with jetting.. ive worked on my carb a coupld times before.. but if i need to go leaner.. what do i need to do?

[slamdak8782]

take the clip off the needle in the carb and move it upa slot and or use a smaller main jet and or pilot jet according to where your getting rich or lean. Id start by moving the clip up. if you move it up to the top and your still too rich go down a main jet if your lean at this point move the clip back the other way meaning down. Basically keep doing that till you hit the best power. I had a 350x and they use the same style of carb as the 300 and the 400. if you have a stock bike you should have stock jetting. With a jet kit usually they give you a bigger main jet and possibly a needle with a different taper.
Think of a pilot jet as low speed
main jet as high flow
and the needle as like a fine tuning for the carb:D

[slamdak8782]

check your compression ratio and make sure your using the proper fuel and that you do not have a weak spark with a spark tester. My 400 will easily jump a half inch gap, try that before messing with all the jetting you could be right on with your current jetting but have weak spark and no amount of jetting will fix that

[crazyatvn]

leaning out you carb depends on where in the throttle it is rich. Adjust the needle first (Move clip up) if that does not help the main jet.

[redrider311]

where is the needle jet at?
and i should move it up a notch or 2?

[slamdak8782]

the needle jet is in the bucket slide you can push it up with your finger and see it move only 1 for starters

[crazyatvn]

Get a monual it will explain everything in great detail.