PJ or PWK?

[royalt67]

Lookin at buying a new carb but I can't find any real recomendations. All the commercial sites just repeat the same ole s__t from the Keihin catalog. So, which is better for MX racing? I'm in the process of rebuilding my son's quad that he races in blaster class. Had a piston seize, probably from a lean mixture, so I wanted to step up the carb to something that more tuning parts are available for, and why not make it faster at the same time?

It has a toomey B1 kit, K&N, open airbox, .020 over, and boyesen power reeds. I am looking at either a 28mm Keihin PJ or PWK for a small increase ove r the stock Mikuni 26mm. I also looked at an OKO, but chinese parts scare me.

 

[mr_3_0_5]

id go with a pwk

 

[245stroker]

The pwk is a newer version of the pj carb. i'd go with the pwk also

 

[royalt67]

Yeah I thought PWK too. It's the catalog statements that confuse me. For PWK Keihin says it's a great motocross carb, but for the PJ they talk about how it gives great response and power at low to mid rpm (MX speeds), and how they are the perfect choice for two-strokes.

 

[royalt67]

and stick with the 28mm? Cause the 34mm sounds cool, but I'm prone to overkill. Of course anything can be jetted down, more or less.

 

[mr_3_0_5]

34 id go big.. lol

 

[specialized7]

ya id go with a pwk forsure.
and the size is up to you, do you plan on porting the motor eventually?
if so you might want to look into 30mm+

 

[royalt67]

34 id go big.. lol

that's the temptation, I'm just not sure if that's not like bolting an 850 double pumper on a pinto. (I'm a car guy)

Anybody have experience putting that big a carb on a mild motor?

 

[royalt67]

ya id go with a pwk forsure.
and the size is up to you, do you plan on porting the motor eventually?
if so you might want to look into 30mm+

Yeah, eventually. Mostly spending money on suspension right now tho.

 

[ruthless_one3k]

The problem with putting a giant carb on a mild motor is that it might not have enough draw to get the air velocity high enough for the fuel to get pulled up through the jets properly, in other word it wont matter how big your main jet is. if you dont have enough vacume to pull the fuel up through the jet it will be too lean. Personally I have the PJ an like it so far but I hear the PWK is better and easier to tune.

 

[245stroker]

I know of one member on here thats running a 35mm pwk on his stock bore, stock stroked motor. Its been ported and the heads been cut and it runs really good. I guess it all depends on which way you want to go.

 

[royalt67]

The problem with putting a giant carb on a mild motor is that it might not have enough draw to get the air velocity high enough for the fuel to get pulled up through the jets properly, in other word it wont matter how big your main jet is. if you dont have enough vacume to pull the fuel up through the jet it will be too lean. Personally I have the PJ an like it so far but I hear the PWK is better and easier to tune.

But you also have the cubes. Sounds like I should go with the 28mm PWK. Damn, I had a good price on a PJ 34, too.

 

[ruthless_one3k]

Th PJ 34 might still be a good carb so long as its ported for it. your best bet would be talk to one of the engine builders they can help set you up with a nice port and polish and suggest the carb that would match it best. The builders on here are Flotek, kennedy_power, and wildcard they are all very knowledgeable

 

[royalt67]

Alright, thanx guys.