another jetting question

[sickmojave]

ok on my 400ex I am running an HMF s/o with the welds ground out of the head pipe, an XR cam, sparks flywheel key and I have 4 1" holes in the air box lid. oh and I'm running a #40 pilot jet and a #160 main. the motor runs great except when I'm in 5th gear wide open. it still runs good but it don't seem to pick up speed like it should. it doesn't miss or backfire at any point in the rpms. just when it's wide open in high gear you can still feel it pulling but it doesn't feel like it has any power. I hope that makes sense. I think I'm too rich on the main jet but I wanted someone else's opinion before I mess with it again. THANKS ;)

[sickmojave]

BTW after a wide open run the plug is a pinkish white color.

[cals400ex]

i would try going down on the main jet one or two sizes. also, are you running stock gearing and tires?

[sickmojave]

yes the gearing is stock and the tires are the same size as stock.

[cals400ex]

i actually did loose some speed up top when i put aftermarket tires on. they are heavier so i guess that is what hurt my 5th gear performance. try going down on the main one or two sizes and see if that helps.

[sickmojave]

thanks cals I will try dropping a size or two. the last thing I put on was my pipe and the 160 main and that's when I noticed the drop on the top end. I have a 157 and 155 I will give a try and see if that helps. the one thing that worries me is the fact that the plug is so clean, not even a little black on it. I'm what you would call an old timer and I have always thought that if it was running rich it would show as black on the plug.


**EDIT** I just read the plug chop thread and I can see the dark ring on the insulator

[cals400ex]

yeah, it is tough to read plugs these days. i still do it but i kind of know how my brand of fuel burns since i have been using it for a couple years. when you do plug chop, make sure you are at full throttle, which you probably knew that. also, i assume you mean a 158 and not a 157?

[sickmojave]

Originally posted by cals400ex
also, i assume you mean a 158 and not a 157?


ooops :p your right it's a 158.