Keihin carb. choke knob

[hotrodaj_2]

I'm playing around with the carb.(Keihin 34mm PJ) to get it where I want it and noticed something I've missed. The choke knob can be turned 10 revolutions. It seems when the knob is turned out the idle comes up slightly. I cant find any info on that damn choke knob. I'm fighting the bottom end and idle a little and this might have a small part to do with that. Does this adj, air or fuel and does it even matter?

 

[Luni]

Yes, on a PJ carb the choke knob is also responsible for your idle adjustment.

 

[Awk08]

/\/\/\/\ correct, but gave me fits, and still oinly gets the idle up a little, i turned it back in, forgot it even existed and adjust my idle with the cable at the thumb throttle, pulling the choke adds more fuel, so i assume thats all turning the knob can do

 

[royalt67]

Sure, this is the main place to adjust idle speed. The brass screw on the side is the idle mixture screw. The 34PJ is not even meant to have the slide open at idle (with all due respect AWK), all the fuel and air for idle passes through the idle circuit. A small bit of air might slip under the slide, but it is basically closed with nothing (not even the cable) holding it open. Pulling the choke just gives you more of it.

When I was pullin out what little hair I have trying to figure out this carb a couple months ago I found that it was extremely sensitive to the float adjustment. It should be 16mm to the top of the float, with the float just barely touching the needle, not depressing it. It works best to adjust it with the carb on its side. With the carb passages nice and clean, you should be able to adjust the idle speed with the knob. Mine is currently about halfway up and it idles great once warm and it needs the choke pulled to start.

If you are in the mood for a long read, here is that thread, all 7 pages of epic glory.
http://www.blasterforum.com/engine-13/another-pj34-jetting-thread-29290/index5.html

 

[super noober]

^^^^^^ i agree, this thread in my opinion is the most complete 34mm pj trouble shooting thread we have. big thanks should go to royalt67 for documenting his issues and the solution so well. I:I

 

[hotrodaj_2]

Big thanks royalt67, I will look at all those pages. I didnt realize your thread got so large. Reps for u. I wish I had a 55 pilot, I think it will be dialed in with a 55 pilot and adjusting the choke knob. I now have a 52 and 162 on a BBK and Oconnor DIY porting. Needles seem to be important too, now in 2th groove (needle high). Ill look into diff. needles also. Thanks guys.

 

[Luni]

I might have a 55 pilot. I dont need anything that high.

If I got one, PM me your address, Ill just toss it in an envelope and send it your way.

 

[royalt67]

I was surprised that I ended up with such a small pilot and large main, but I just kept giving it main until it didn't go any faster and even bogged a bit on the top. At that point I dropped the main a bit (now 170) and started looking at my boggy low end. To my surprise it really responded to decreasing the main down to 40. Certainly everyone's modded engines are going to require different things, but consider it food for thought.

I currently have the DGH needle in, but one of these days I need to get around to trying that CEL like Noober's, since I already have it.