I have a 39pwk on my race mod, I have an 8" K&N clamp on filter, I rejetted it to a 170 main jet (180 previous), and fixed a small leak on the bottom of the bowl and now it will only run on half choke. Am I getting to much air and not enough fuel, or vise verse?
Any help would be great! THANKS!

 

did you maybe mess up the choke adjustment

 

I wouldn't think so, but sometimes you don't have to do much to a carb to get it all out of shape.

 

Half choke needed says needs more fuel/richer mixture. I'd say you might have an air leak around the intake or boot on carb now after you rejetted. Your close I'm sure in the 170 range. I'd say check for airleak first. I grease the carb before I put it in the boot and get your clamp tight. You can spray carb cleaner around the intake and see if it changes the rpm of the bike. Some brands speed it up some slow it/bog it if it has a leak. You might check for a leaking base gasket too. Otherwise make sure you dont have a piece of dirt in carb clogging the pilot jet some or sucking dirt from the floatbowl up in the mainjets passage. Hope this helps.

 

If it won't idle without the choke, then you probably have some crap in the pilot jet. It doesn't take much -- just a speck will clog it solid. Your pilot jet controls fuel @ idle to about 1/4 throttle, then your needle comes in from 1/4 - 3/4, then from 3/4 to wide-open is your main.

By changing your main from a 180 to a 170, you went leaner at full throttle. That won't affect starting or idling. If you don't have any air leaks as mentioned before, I'd just clean out the pilot jet and all associated passages with some good carb cleaner (I use Honda brand from a dealer---works excellent), and a tiny piece of wire...REAL tiny (you don't want to force anything in there). If you don't have a wire that will fit, then just blast it real good with the carb cleaner.

 

16polaris I remeber one time you said your carb didn't have an overflow did you get it from RCR/HPD or did you get it online somewhere/used?

just curious I bought mine online(ebay) and had to change a ton of parts I had a similiar situation and I have the wring needle/seat in it. HPD uses a big one.

 

I bought it off a guy on www.planetsand.com. The carb ran GREAT and idled GREAT, but after I rejetted it, it was still fine but I took the bowl off to check the gaskets to maybe fix the small leak and after that it just stopped idleing and if it does idle when I pin the throttle it dies. I will take it back apart this weekend and clean it out and maybe that will fix it? Thanks for the help!

 

pull the bowl off and remove the float and needle and seat. I have a feeling you have a different needle and seat.

HPD uses an oversize 3.5mm and standard they come with 1.5mm's(most do). you could probable make the 1.5mm work but none of the hpd guys jetting specs will work for you. I would say tis is your problem or the floats may be getting stuck somewere.

 

Yeah i'm going to pull the carb out this weekend and give it a good going over and check everything out really close, I may have to try different jets also.
Thanks for the help!