Main vs. Pilot Jet on non-CV Keihin Carb

[kirchnerjd]

Hi everyone! So glad to be a part of the Forum... Thanks for everyone's help!

So, I have a de-restricted Genuine Roughhouse 50cc with a hor. Minarelli engine and small (13-14mm) Keihin carb. Aside from the exhaust and CVT variator restrictions being removed, it was a stock scooter before this round of tinkering. I removed the snorkel from the airbox and to balance things a bit I also up-jetted the main from an 82 to 85. I don't see an easy way to adjust the needle height and I left the pilot jet be at the stock 35. Now, it is running good from 2/3 throttle to WOT, but from idle to 1/4 throttle or so it is running very rich... I've tried to adjust the A/F mix with poor results at low speed/idle. Is this a normal reaction for the adjustments I've made? I have removed and cleaned the carb and check for vacuum leaks as well as set the float height, etc. What, besides using a smaller pilot jet, would you guys recommend trying?

Thanks everyone! This is really a great scooter... It runs great when in tune, I hit 52-53 mph (stock speedo) on a flat, open road earlier! I just can't get the low speed mix quite right... If I could only get this straightened out so I could get the CVT in tune, I'd be a happy camper! :scoot2: What should I do?

[dr1445]

since you have more air flow you have a lean condition in the midrange, which is controlled by the needle. the needle needs to be raised to allow more fuel flow. if there is no eclip slots to adjust the needle you can go to the hardware and get a small washer. place the washer to lift the needle. note, i have seen some carbs where material from a nylon spacer must be removed to raise the needle. typically a #4 washer about 1/32" [.030"] thick will do the job.

[90GTVert]

:welcome: to the forum.

35 sounds huge for a stock pilot, but I've also never seen a Keihin on a horizontal minarelli. The other carbs tend to use closer to a 20 pilot. Was it rich at low throttle before the mods? The only thing you've done that I'd expect to make it more rich is the main jet. Otherwise the airbox mod and exhaust restriction removal should have both leaned it out more. Are you sure it's rich and not lean?