New to Keihin carbs need a jetting ballpark

[Midwayusa]

Working on a Blasty for a friend. Has a Toomey B1 pipe and silencer, Keihin PWK 28, very nice port job but unsure of what the porting is set up for, and soon to be .020 over bore with Wiseco piston. This thing still had the stock piston in it and it is melted. I am unfamiliar with these carbs and don't want it melting down again.

On my Banshee I am at 280 mains with Mikuni's and FMF pipe and it is all good. Another friends Blaster is at 270 main on a Mikuni with FMF pipe. Just worried about getting the Keihin in the ballpark and preferably a little rich so when the weather cools down it will be about right.

Right now the carb has a 152 main and a 45 pilot. What little I could find of people with similar setups have me leaning toward a 162 main. The altitude here is around 1100 ft and he plans to use a Uni Filter. Also no airbox lid.

Anyone have any suggestions?

 

[Kgibson]

I would do the 162 but I think it will be rich. Better safe than sorry and you can work your way down after breakin. You might have to change to 48 pilot...you'll know after you fire it up.

 

[Midwayusa]

I would do the 162 but I think it will be rich. Better safe than sorry and you can work your way down after breakin. You might have to change to 48 pilot...you'll know after you fire it up.

I don't mind being a little on the rich side of things. On my Banshee I keep it jetted for the 60-80 degree stuff and when it gets hot out I just pull the lid. The parts guy at the local dealer said to try 160-162 and keeps jets above and below that in stock.

 

[royalt67]

Current jetting is in my sig. I have a 162 in a similar setup and it runs great, if anything it might be a tad rich, but it doesn't foul plugs at 4000 ft and it runs even better lower. No lid is the only way to go. Think of your pilot as a "throttle response jet".

 

[Midwayusa]

Current jetting is in my sig. I have a 162 in a similar setup and it runs great, if anything it might be a tad rich, but it doesn't foul plugs at 4000 ft and it runs even better lower. No lid is the only way to go. Think of your pilot as a "throttle response jet".

Thanks for the input. Now just waiting on him to get me parts money so I can order the parts and get to machining things. Going to soak the pipe in our tank for a few days, and get the carb cleaned and ready to go. Hope it lives!!

 

[Midwayusa]

Ok so I get the carb completely apart to clean it. Clip falls off the needle and the needle falls out in my hand. A little concerned that the needle groove is worn and you can see wear on the clip. So.... I go to the dealer to get a new needle. Turns out the carb is like an OEM off a Kawasaki possibly and the parts guy tells me the needle is leaner than what he normally sees. It is marked N68A. Suggests I put a JJH back in as that is the standard needle when you buy one of these carbs.

I really don't want to melt this thing down right off so does anyone have any other suggestions on the needle, or will this and a 160-162 main get me close till I can do some plug chops.

 

[royalt67]

Standard jetting for a PWK 28 (aftermarket)
Main, pilot, needle, slide
#135 #38 46JJ8 C.A.3.5

Mine is the aftermarket version and works great with the 46JJ8 needle. I can't remember if I have it on the 2nd or 3rd slot, but if yours is worn it should be replaced.
FWIW, Sudco sells a kit (pn 020-112) that has all wear parts including a new float needle/seat, air screw and idle screw. This would be good for renewing a worn out carb and of course as the West Coast distributor they have all possible needles and jets.

Sudco International - Modern and Vintage Replacment and Performance parts for Street Bikes, Dirt Bikes, ATVs and Personal Watercraft

 

[Luni]

Jetting really depends on elevation, humidity, etc.

Im riding around 8000-10000 feet. Im running your carb, 132 main, 35 pilot, clip on third position, idle screw about 1.75 turns out.

I run a bit rich with this setup, but Im at elevation. I also have an FMF fatty, and a Maxima filter, open lid on the airbox.

In general, the way I find a good jetting point if I dont really know where to start is Ill go what I think is stupid rich on the main. Then Ill ride it, if it bogs at WOT, Im too rich. Ill pull main back until it doesnt bog anymore, then I might even go down 1 or 2 more after that and do plug chops till I get it right.

As for the pilot, those are relatively easy. You get it to the point where on a cold start you have to choke it, on a hot start you dont. It will idle, and you dont have to adjust your airscrew more than 1.75-2 turns out. If you have to go more than 2 turns out to get it it to idle, you are too rich on the pilot. If you can idle with the screw turned all the way in, youre too lean.

Needle position is more of a throttle response/midrange adjustment, so you will want to play with that after you get your main and pilot situated.

And I gave you info backwards, sort your pilot first, then the main, then the needle position.

 

[Midwayusa]

Standard jetting for a PWK 28 (aftermarket)
Main, pilot, needle, slide
#135 #38 46JJ8 C.A.3.5

Mine is the aftermarket version and works great with the 46JJ8 needle. I can't remember if I have it on the 2nd or 3rd slot, but if yours is worn it should be replaced.
FWIW, Sudco sells a kit (pn 020-112) that has all wear parts including a new float needle/seat, air screw and idle screw. This would be good for renewing a worn out carb and of course as the West Coast distributor they have all possible needles and jets.

Sudco International - Modern and Vintage Replacment and Performance parts for Street Bikes, Dirt Bikes, ATVs and Personal Watercraft

Royalty67, what is your altitude compared to mine? I am at around 1100 above sea level.

 

[Luni]

Hes like.. 4200 feet? 4800 feet?

Hes higher up than you.

 

[Midwayusa]

I am beginning to wonder if this thing has a crank seal out based on some of the stuff I am finding. I think I might dummy the jug and head back on and pressure it up and see if it leaks bad. Sure hate to put it all back together with new stuff then find it leaks. As far as I have it torn down, now would be the time to do seals for sure.

 

[royalt67]

Just replace 'em all. Good insurance and here is a damn good price.

YAMAHA BLASTER COMPLETE OIL SEAL KIT CRANK-TRANS CASE: eBay Motors (item 200444500707 end time Aug-26-10 12:20:24 PDT)

 

[royalt67]

Royalty67, what is your altitude compared to mine? I am at around 1100 above sea level.

I am at 4100 here, but where I last raced with that carb and jetting it was about 800. I just haven't leaned it out since then cuz it runs so nice. Like I said before, it is a bit rich for here at home but it doesn't quite foul plugs.

 

[Midwayusa]

Engine passed leakdown as far as crankcase seals. I am happy now as I have half what I need for leak testing my Banshee. So for the Blaster, larger jet and different needle and proceed with top end rebuild. I think it will be good as the guy has given me plenty of tuning time before delivery so I can do plug chops and get it right.

Thanks for the help and I will be lurking here to see what is new.