Jetting help

[K-Dub]

I bought a used 450r from northern Minn, and brought it to south eastern OH. It had less than 5 hrs run time on it. It has the HRC kit put on at purchase from the dealer and everthing else stock. Now here is my problem it backfires and sometimes backfires and stalls when I let off the throttle also has a hesitation when I first shove the throttle wide open from full shut. Second thing after riding it hard for about 5 hrs yesterday the muffler is carboned up. Havent rode for 9 yrs but had 15 yrs riding and racing exp on 2 strokes prior. This is what I think I need to do (no four stroke jetting exp) go richer on the pilot and 1 notch leaner on the needle and drop the main jett as most of the time when I ride its half to full throttle. I also turned the idle up a bit, this seemed to help with the backfire and stalling problem, but dont want to leave it that way.

1 more question, does twin air make a good air cleaner for the 450r? I read alot of the air cleaner threads on different sites but didnt see anything about twin air. That is what I ran on my 250r and CRs.
Thanks for the help.

[BOONE450R]

I would try the main first, then play with the needle. Have tried to adjust the Air screw?

[DirtDevilBT]

With the soot on the pipe that means you are running waaay rich. There is a chance the wrong main was put in. The place you bought if from, will they look into it. I mean, the valve clearances and what not?

Try this or just make sure you this is what you are at, good starting point anyway. 2 turns out on the mixture screw, middle or one notch below middle on needle, and I don't know what the HRC main is but it should be bigger than a 118. Prolly not too much bigger since you don't have a pipe.:confused:

[K-Dub]

I bought it used in Minn. and I live in Ohio, the dealer that installed the kit is over a 1000 miles away. So taking it to them is out of the question. Im going to take the carb apart and see what jetts are in it monday. You said the main should be atleast a 118, I see some people running 180, 185 and 190 mains. Why such a big differences in the numbers?

[walt miller]

the main for a hrc kit is a 185 and stock is 118. mine did the same thing right after i installed my hrc kit played with it a week and found out i had bad gas. had to dumb gas clean carb.

[White7]

This might clear thing up a bit and head you in the right direction

http://www.trx450r.org/forum/index.php?showtopic=1657