Keihin Cr Special Carburetor Tuning Manual Arts. 4/29/2017 0 Comments Bike Description Price Year Location State Listed Source; WR250R: Yamaha WR250R WR250X Hi All.

I had bought a nice set of used Keihin CR's from a member here a while back and had finally got them ready and on the bike. They ran pretty well at half throttle and above but were pretty bad at idle to 1/4 throttle. No worries, I thought, I've been through this with stock carbs plenty of times. Synch carbs, clean pilot and main jet passages, check float levels, check for vacuum leaks, recheck ignition/plugs/wires, etc. Everything checked out fine but still #3 pipe was barely getting warm. After staring at the parts diagram for a while I finally had an idea what might be causing this. Seems the 'choke' on these carbs is not the same thing I am used to on the stockers.

It's actually a 'starter' circuit with it's own fuel/air supply and runs independent of the pilot or main circuits. When the choke lever is lifted it raises a starter valve in each carb that allows air in from openings on the side of each carb and also pulls copious amounts of fuel from the 'starter' chamber in the float bowls.

It then dumps this mixture through a rather large hole in the carb throats and straight into the engine. What was happening to me was that fuel had dried in the area that the starter valve seats. The starter valve is similar in shape to the plunger in a master cylinder and is pushed down by a spring in order to fully seat against the carb body, just above the emulsion tube leading from the starter chamber. Dried fuel(gunk) was preventing the valve from seating and was keeping the starter circuit open. #3 wasn't heating up at idle because it was choking on fuel. I dropped all four float bowls and sprayed tons of carb cleaner up each emulsion tube while working the choke lever up and down. Now when the lever is closed, so are all four starter circuits and the bike idles well at 1100rpm.

There was not a lot of gunk removed, meaning it does not take much to foul these circuits up. Figured I'd post this in case anyone else has trouble getting a good idle to 1/4 throttle with their CR's. Now I FINALLY get to do some proper carb tuning. I just acquired a 1976 cb750f that has CR special carbs. Kalam baba bulleh shah pdf to docx. Unblock proxy sites. I am having a tuning nitemare!!! I know Cb750 have some 'character'. But this thing is unridable!

I am a semi-experienced motorcycle mechanic, but still can't tell what is wrong with these touchy cr specials. The only thing I know for sure is that the idle/slow circuit is waaaay to rich, but when it comes on to the needle it acts really lean (cuts out 'rich?' And the revs hang up,'lean?' I cant get the thing to rev high enough to come on to the main jet (rich?) Sudco has been no help to me at all.

Does anyone have a similar setup? I am running a Kerker 4 into 1 with a very free flowing comp baffle, stock engine, 29mm cr specials, dyna 2000 ignition. Here in the city of San Francisco, it costs around $650 for a dyno jetting session, plus the cost of jets and tuning labor. I'm too poor for that.

Any racers out there have some proper jet size/tuning guidelines for me? I seem to have run into a D.P.O.- a dip #$%* previous owner. Thanks for your help, I really want to ride this thing -jhase, SF,CA. I just acquired a 1976 cb750f that has CR special carbs.

I am having a tuning nitemare!!! I know Cb750 have some 'character'. But this thing is unridable! I am a semi-experienced motorcycle mechanic, but still can't tell what is wrong with these touchy cr specials. The only thing I know for sure is that the idle/slow circuit is waaaay to rich, but when it comes on to the needle it acts really lean (cuts out 'rich?' And the revs hang up,'lean?'

I cant get the thing to rev high enough to come on to the main jet (rich?) Sudco has been no help to me at all. Does anyone have a similar setup? I am running a Kerker 4 into 1 with a very free flowing comp baffle, stock engine, 29mm cr specials, dyna 2000 ignition. Here in the city of San Francisco, it costs around $650 for a dyno jetting session, plus the cost of jets and tuning labor. I'm too poor for that. Any racers out there have some proper jet size/tuning guidelines for me? I seem to have run into a D.P.O.- a dip #$%* previous owner.