Help out w/Powerjet ?'s

[PowerFiend]

95+ KDX200's came factory with a 35mm PWK.

A popular mod for the later 200/220 is to bore to 36mm and put in an intake divider plate from:

www.rb-designs.com

[Hillclimb#42]

Well, the work was done before we got the bike. What does machining the slide do to performance?

[DoldGuy]

#42,
The machine work on the Slide I assume is on the cutaway. The cutaway is another part of the jetting process. If you look at the slide you will see a number on it which shows the "Size" of the cutaway (in mm). The larger the # the leaner, the smaller the # the richer. The cutaway affects mostly 1/4 throttle. A way some people change slides is to simply grind the slide to a desired height to avoid purchasing a new slide as some of the slides can be a little costly. Yes the larger the bore of the carb the more topend with a sacrifice of some bottom. To answer your previous question the Power Jet is just another circuit you can use to help with the jetting & generally more pre load on the power valve softens the hit, but you can have them open too late a hurt it's performance. As many members here have stated, try only 1 thing at a time to understand it's good qualitys & bad. Hope this info answers your questions.

[DoldGuy]

Well I am finally pulling my 250 out of mothballs to get ready for next weekends race & thought it would be good to take some pics (makes things alot easier to understand) while cleaning the carb. If you notice the Float Bowl has a hole in the side which feeds fuel to the base of the carb (in which you see a small jet to the side of the bottom of the carb & has different jet sizes). The Picture of the solenoid shows the pindle which will close of the hole at a RPM determined by the CDI box (this point is adjustable on Most Programmable CDI boxes). And the last picture actually shows the Power Jet Dump Tube & its height (this particular one is quite low & will start to have a vacuum pulled at about 1/4 throttle) in which are different on some of the PWK models. As stated earlier, the Power Jet can be an additional means of Jetting even without it hooked up electronically, you just dont get the added benefit of it leaning the bike out all the way up top.

Hope these pics & info is of help.

[DoldGuy]

Boy am I getting old, forgot the pics

[Hillclimb#42]

 Well, related topic, but a bit of a change in direction. I learned something, I thought I might share.
We went back to the stock carb (mikuni) and played with adjustments, went back to the powerjet and then back to the Mikuni. The mikuni idled easy, but was always fat on the highest part of the rev. It took alot of revving to clean-out. The powerjet on the otherhand ran clean, had plenty of top-end rev, but no power under a load. After going back to stock carb and airbox, we still had no power while under a load. The old 86 mikuni didn't even have a mixture screw. Thereby adjusting mixture with the needle and the jets. That got us close, but it was the float adjustment that fixed it. They were a little high which caused it to be too rich going up hill, under a load. The float adjustment was the most noticeable improvement. By setting them to close sooner, we leaned the mixture and gave us our revving and power back.
 You guys having trouble with rich condition at top of the rev and missing some mid- range power might need to check your floats. It matters.