PWK throttle valve #

[regg187]

How important is the throttle valve in overall jetting,

I got a 36mm airstryker and had it bored to a 38. the body dimensions are the same for both, except the 38 comes with a #7 throttle valve and the 36 came with a #6 throttle valve. I have put in the keihin recomended jetting to start with #55 pilot and 170 main and a DGJ needle, but I am wondering how much 1 jump on the throttle valve is really,. I have found them for 55$ +shipping if I really have to but am asking if anyone really knows.
thanks

[Buttermilk]

The 6.0 throttle valve is richer than the 7.0 throttle valve.

However, in my experience, which is minimal, you can make either one work.

I'd run the 6.0 slide, if it were me.

[C-LEIGH RACING]

More angle the slide has, more air it will flow.
Think of the carb slide as a blade of sorts covering a tube or pipe.
If the blade is just straight & has no cut angle on the edge, as that blade is opening up & when air flows under & past the blade with no cut angle at the edge, it has to stop & then curve under the straight flat edge causing a distrubance in the air flow.
With an angle cut at that blades edge, when the blade is opened up, the air flows not distrubed & can flow smoother & faster under the blade & across the jet nozzle.
So, more angle, or cutaway, cleaner & faster the air flow.

Dont go to grinding though thinking more angle better it will work, cause there can be to much angle or cutaway & cause the slide to function worse than no cutaway at all.
Neil

[regg187]

Thanks for the help, I am going to try jetting with the 6, and if i can't get it working good ,I'll buy the 7. I had no intention of grinding on that slide , Neil. lol

but just in case what would one use, in the old days of round slides they used belt sanders to add cut away .... but this is a funky D-valve. just kiddin' wouldn't even try it;)

[Buttermilk]

Here's a dyno chart showing a 38 PWK A/S vs. a 41.5 PWK.

The 38 has a 7.0 slide, a 168 main jet, a DDJ needle in middle clip position and a 55 pilot.

The 41.5 has a 6.0 slide (richer), 168 main jet, DDJ needle on richest clip postion, and a 55 pilot.

Very similar AFR as you can see by the AFR curve.