my buddies 250 well 310 got eaten when we went to sandmountain the crank went out in it and it has been down for about 6 months. We just went through it and put a new honda crank and it runs great. The only problem is with the jetting. I am running a 225 and i think thats the biggest main jet they make for the carb its an aftermarket esr carb that came with the 310 i cant think of the name right now i think its a pwk though?? I have always just changed the main jets i never have played with any pilot jets. How do i go about changing the pilot jet and can i even buy bigger pilot jets for this?? I know this is a stupid question but i never have really toyed with the carbs on any bike other then swapping the main jets out for bigger or smaller i feel so ignorant right now.

 

It probably is either the 38 or 39 PWK. They also have the bored 39 that is a 40.5. Between my wife's bike and friends we run a 265,310,330,350, and a 370, all by ESR. The 3 biggest motors have the 40.5 carbs and none of them run over a 190-195 main jet even in the colder weather here. We are about 800 feet above sea level. If you are at sea level then you might need a size or two bigger, but definitely shouldnt need a 225 by no means. You should start with the air screw at 2 turns out and start with a 52 or 55 pilot jet. Also start with the needle clip at halfway. You reach the pilot jet by removing the carb bowl and taking a small pocket screwdriver or similar and unscrew the pilot jet. It will be next to the main jet but a little smaller and have a round head. It will be a little longer than the main jet and have holes in it on one end. The size will be on the side in very small numbers. You can do a search on google and find all the info you need for tuning in those carbs. You want an overlap in transition from the idle circuit, part throttle, and wide open throttle for best performance. Hope this might help,Bubba

 

This is what i found out the biggest jet they make is a 230, and i am running a 225 in my bike. I am at sea level here in CA. I wasn't able to find a piolet jet for the 39mm pwk, but i did find a slow jet. From what i was told the slow jet is only at low rpm so i dont have to worry about that. My needle is set all the way at the top and my plug is still running very lean. I am going to go down on the needle size, and hope that it fixes my problem. And my air screw is set at about 2 1/2 to 2 turns out. I am not really sure about any of the other things with the carb, but i did check to make sure the float level was also correct befor I put everything together again. It has been really cool and rainy out here so i dont know if that will change any of this, but i hope the needle changed things for me.

 

Other than the air screw, the PWK only has a main jet and pilot jet. I believe the pilot is what you are referring to as the slow jet. Going up on pilot jet size will also affect main jet size at WOT. If your plug is lean at WOT then I would suspect you have an air leak somewhere. I have never heard of anyone having to run that big of a main jet in a Keihin.

 

Well I am sorry to tell you that I also run a 220 in my 250r quad that has been ported on a 40.5mm carb i dont know what it is they just like to run like that? They are not running fat or anything and I havent had any problem at all so i dont know what to tell.

 

Well, you came in here like you didnt know a darn thing about carbs. You didnt even know if it was a PWK and now you talk like you know your stuff. Sorry I tried to help, sounds like your on the game.

 

im really sorry i wasn't sure if it was pwk i though ti might have been a pj or something else so i wasnt so sure and I didn't want to give wrong info. Like i said i can jet pretty well its just the whole slow jet or piolet jet that kinda confused me. I think if i played with the piolet jet more or i talked to someone who knew a little mrore about them I am sure that I would be using a smaller jet so thats where I am kind of confused and wanted most of my help, but like amny other I can see no to many people toy with them very often. All i can say is that it isa lot easier to change a jet in a 250r then a banshee man I hate jetting it and it takes like an hour just try to get everything right. I am sorry that I came off like a retard, but truthfully when it comes to the piolet jet or slow jet i really am. Who is to say my bikes are not running lean on the bottom and fat on the top? I dont know i was just hoping to talk to someone with a lot of knowlege about this sort of topic.

 

OK, I found a great site that might help you out. Should be here Carb tuning
Hopefully that might fill in some missing info for you. Your right though, not a lot of people get into more than just changing the main jet. Good luck, Bubba

 

I don't know whats going on, but I have not heard of someone needing a main jet that big either!
My 330R only took a 168 main, and my built 250 right now takes a 195 (fully ported and polished).

You sure you don't have an air-leak somewhere? 225 just sounds crazy![img]i/expressions/face-icon-small-shocked.gif[/img]

 

Here is what we use.

20 deg. F and 700 ft above sea level.
48 pilot, DGH needle middle notch, 185 main

70 deg. F and 700 ft
42 pilot, DGH middle, 178 main

The plug comes out golden brown around the electrode hook and turns to black around the outside of the plug. None of the plug is wet or shiney, all colors look like flat style paint, no gloss, and with tiny trace amounts of carbon on the plug.