This weekend my friend who works at a Polaris dealership installed the Kehin PWK 39mm for my 2001 Scambler 400. The intalation was kind of a pain, but we took care of it in about a half hour. We started at the 172 jet setting (highest Rick gave me) and it was way too rich. We eventually brought it down to 168 and after checking the plug it was pefectly tanned. If I went down to the 165 setting I think it would have been too lean, especially with the 50 degree nights. Anyhow, my cousins 99 400 Sport was smoking me after the installation of the PWK. When I had my stock 34mm Mikuni I always edged him out, off the line and on the top end. Clearly it seems the 39 PWK is better suited for an engine with some porting. Is there anything else I can try doing before I go back to stock. I may eventually do some trail mod proting to the motor, but definitely not this season. Do you think boring the stock carb to 35.5 is worthwhile? Thanks.

 

I personally don't think the bored carb works worth a darn. I had one that performed just awful. The throttle response was never there it ran out of fuel on long runs(Mine was trail ported). It just plain stunk. The stock carbs I don't think work very well with modded motors. There's some on here that will tell you different but my story is stated above. The 39 outperforms the stocker and all other carbs hands down. There was a 39 thread that got a lot of responses a week or so back. You might do a search and get some more info from it. Good luck with you tuning.[img]i/expressions/face-icon-small-smile.gif[/img]

I agree it is hard to fit that big opening into that little carb boot huh?

 

You need to make sure the slide is opening all the way when you are wide open.Pull the filter off and check it out.

 

well our mods are almost exactly the same. yes its an absolute pain to get the carb in the boot after 3-4 times it streaches out and its not as bad. Are you running some type of adaptor for the stock air box?

My quad is definatly faster with the 39mm. I raced my buddys z-400 with a dialed in 34mm and we went neck and neck until we ran out of room. with an out of tune 39mm I would gain about 6 inches everytime he shifted. I havn;t raced him with mine dialed in but I can;t wait too. Looking at your mods the only other thing I have you don't is my 12 to 1 head. I had a local machine the stocker 0.020in and I run premium fuel pre mixing.

I havn't ported yet becuase I would like to wait for my next bore job.

 

as soon you get the porting and heads you will forget the stock carb forever along the mods you already have on it.