03 400ex hot cam stage one k&n air filter t-4 slip-on I tried rejetting the carb I went from stock to 155! Ran fine but I was think it was alil lean soo I changed it too 170 and change the oil to mobile 1 15/50 now at almost full throttle it backfires and spits any ideas ??? I live in fAyettevile nc 240ft sea level!! Maybe change to some better octane fuel ??

 

Try a 158 and 160, with a 42 pilot, fuel adjustment screw 2.5 turns out from seated. I would think a 170 would be way to rich. A 170 is where I would start with a modded 416. Do you do the plug chops, if so what does it look like?

 

I'll try it out tomorrow also the valve cover is leaking oil out and the drain plug is stripped all from the pervious owner any idea on how to fix ??

 

You can get a new gasket for the valve cover and find out why its leaking. The drian plug, tap and replace?

 

Stupid question should I put rtv on the gasket??

 

I got rid of the gasket and use yama bond. clean both surfaces real good and wipe with brake clean .. thin on some yama bond and reset cover. let dry. good for long long time.. I would not use rtv ...

 

Ok thanks I'll give that a try

 

do not do that the metal gasket acts as a shim for the cam,put a thin coat of yamahabond on the gasket and it should not leak