While rebuilding my 38 Kehin, I took the choke assembly apart. I didn't actaully get it all the way out though. Rather than break it, I reassembled the choke (read: screwed it back into the carb). Now not only does the choke not work (it won't pull up) but I have a mysterious issue with the engine not running back down to idle after some full throttle maneuvers. My question to the forum is: on Kehin carbs is the choke removable? If so is there anything that can be gummed up in there that needs cleaning or something? Thanks

 

Well I'm scratching some old brain cells here but back in the late 80's I had a Honda 250R that had a Kehin carb. In my usual upkeep I would do just as you did...screw the choke asmbly out and spray carb cleaner all over the brass plunger and its threaded piece while moving the plunger up and down. I would then spray carb cleaner into the hole it came out of, then into the air cleaner side port. There is not really anything as far as moving parts in the choke area that could create your engine not returning to idle that I am aware of?.? Did you cross thread the plunger? This could cause it to not pull out easy. Did you over tighten it, again it has been over ten years since I have worked on one but I think the threaded part if overly tight could cause it to stick. Finally when you put it back toghter I am reading that you rebuilt it. If you replaced some of the parts like the slide or needle or the piece the needle fits into when the engine is at idle the original air screw settings may not be what they were when the above mentioned parts were worn out to. The carb may not be allowing as much gas into the engine with the new parts and this could create the lean engine rev it sounds like you have had? Let us know what you discover.

 

If your Keihin carb is like the ones on Kawasaki Bayous, the part you speak of ain't really a choke, man; it's a fuel-enrichment starting system!

The "choke" on a Keihin actually is a plunger that dumps raw gasoline into the mixture stream; it works by withdrawing a plunger from a hole, letting the gas flow.

There is an article up on "Tech Tips" on the ATV Connection Magazine home page (at least it WAS up) regarding Keihin carburetor maintenance; I believe that piece will tell you what you need to know, if your carburetor is the same design type.

The "choke" plunger must be absolutely straight and aligned so it will fit its hole when closed; otherwise, your carb is in a perpetual too-rich situation.

The plastic plunger lever cap is the most miserable of parts to replace, unless you remove your tank and get good access with very nimble fingers, and maybe even a bite or two with a 12mm open-ended wrench--moving the "choke" lever to "on" helps get the thing started, BUT: that plunger must be perfectly aligned to work right--if you bent the plunger end or screwed the cap on with the thing crooked, you're in deep trouble--the plunger must be aligned so it goes directly into and out of its hole.

An exploded parts diagram is available a buykawasaki.com; possibly similar to your Suzuki carb.

Tree Farmer

 

What is the letter designation of the carb? 38mm doesn't mean much. For instance, I have a 39mm PWK Keihin on my LT500. On this carb, the choke can simply be screwed out and removed. However, many former Honda dirt bikes equiped with Keihin carburetors had a different choke system. Turning the **** on the choke would raise or lower the idle of the machine. This may be what you are experiencing.

 

I do not actually know what model designation I have. This carb was on the bike when I got it. It has an oval shaped slide and it has the idle setup that you describe for older honda dirtbikes. The "choke" know is screwed up for higher idle (leans the mixture for the low speed circuit) or screw down for lower idle. Like I said before I am unable to get the assembly off of the carb. I made the original post a couple of days ago and have not had time to go out and work on it. I'll have time tonight though and will post tomorrow with my findings.

 

Yes, my carb is a PJ. It says right on the side above the float bowl PJ in big letters. I missed it before. Anyway I took the thing apart and sure enough I did not have the small plunger lined up right. No wonder the lever would never pull up. Now that I have this seated correctly, I wonder if my engine run-on will continue. It sure is scary to let off the throttle and have the quad keep on going like the throttle is still WFO. Thanks for everyones help.

 

I am not sure if it is your carb or not but turning the **** (funnel looking part) on that plunger is what actually sets your idle speed. I cant remember which way your turn it but that will adjust your idle speed. I had some CR's from that era and that is the way they worked.

Joe