on my friends 2001 400 scrambler he installed a pipe and clutchkit witha k+n.he put in a 260 main jet. we cut another hole in the top and cut out the water shield and cut down 2 inches on the bottleneck and it would not run right.it was leaning out too much.what jet to go to now or what should i do.

 

That's a tuff question, No matter what mods you have done the plug is what you have to look at.Make sure you do a full throttle run and look at it, also do a half throttle too.
I run a 290 in summer and a 310 in winter, that's what works for me.
I also keep an eye on exast temp now.(alittle gun shy now)
Good luck, Keep it rich and work backwards.

 

I had to change 2 jet sizes when I went to Ritter's $35 modified air box w/ UNI filter kit. The best $35 I ever spent. I could tell the difference.
Jim Maloney 98 400 Scrambler
http://y42.photos.yahoo.com/jim400scram

 

Howdie,

At one point in time, I was running this exact same setup except I am at 2k ft. above sea level and I was running a 270 main in the stock carb.

Hope this helps,

EC

 

I have the Ritter mod and I'm running a 270 main also. The only problem I've noticed is that it goes way too fast. My son on the Honda can't keep up.