Starts well and then drowns!

DianneB · Post by **DianneB** » Sun Aug 30, 2015 7:55 pm

I don't know if the main needle is supposed to close off the main jet when the slide is all the way to the bottom but, on mine, it was nowhere near close to closing, even with the clip at the very top of the needle.

Not knowing if/maybe some parts may not be original to this carburetor and after doing numerous careful measurements of how much the needle had to protrude into the body (toward the main jet) to close off the main jet, AND knowing that the engine was running horribly rich, I decided to shorten the main jet holder to get the needle closer to closing. I machined 0.040" off of the jet mounting face and another 0.040" off the other end (as much as I could without hitting the tiny metering holes.

I reinstalled the carb, started it up, and went for a ride - HUGE improvement! The mixture still needs some tweaking but it is a whole lot closer and no longer drowns. When accelerating it no longer tries to down but GOES!! :)

Getting a whole lot closer to right.

brewsky · Post by **brewsky** » Mon Aug 31, 2015 4:37 am

Here are the correct needles/measurements:

Keihin ....marked K22401 (best)
or
Keyster ..marked D3

needle clip in middle slot

float at 26.5mm (measured from notch in side of carb body)

DianneB · Post by **DianneB** » Mon Aug 31, 2015 5:08 am

Thanks!

brewsky · Post by **brewsky** » Mon Aug 31, 2015 6:28 am

DianneB wrote:Thanks!

No problem!

My dream went through the same blubbery rich conditions in the beginning.

Turned out to be too large jets supplied in the Keyster kit, as well as ME setting the float to the WRONG 22.5 mm (superhawk) spec.

DianneB · Post by **DianneB** » Fri Sep 04, 2015 6:30 am

After modifying the main jet holder (NOT recommended!) there is a big improvement in the mixture from about 1/4 throttle upwards but I still can't get the lower throttle settings leaned out no matter when I do with adjustments. Even my engine-builder/retired-bike-racer friend (the most knowledgeable and experienced bike mechanic I know) is puzzled. Everything seems to be marked right and there is no apparent damage to the carb or any of its parts but something is wrong.

Being out of ideas, I have picked up another carb from a motorcycle salvage yard and we will see if it makes any difference. The idea is to install the second carb "as is" and see how it behaves. If it works well, then I can compare the two and figure out what the difference is.

G-Man · Post by **G-Man** » Fri Sep 04, 2015 11:56 am

Good plan....

G

bamacl · Post by **bamacl** » Fri Sep 04, 2015 11:30 pm

The needle jet and needle are wear items in the carb. The position of the clip changes the taper of the needle in relation to the jet. Higher =leaner, lower = richer. That said over the years with use, dirty or no air filter, ect they wear to the point that you can not lean the mixture out enough. It shows from idle on up. Some kits have them in there or check with LM or Ohio cycle. Solved many a persons carb problems by changing these.