Jet size:

[zbuck]

I recently install a 47MM kit in my scooter. Other mods UNI air filter and modded exhaust. Stock cam and head. New carb. had a 78 main and 34 idle jet, changed to a 85 main and 35 idle jet. Done a plug check, running way rich, black soot on plug, should I go back to jets that came with the new carb? Thank you, Don B.

[Rebel]

is it getting soot out the tail pipe too?

Sometimes you get a bad plug read if you run it and let it come back to an idle before turning it off. You might try running it at cruising speed then hitting the kill switch and checking the plug after it cools down a little.

[zbuck]

Rebel, Thank you for your reply. Yes there is soot in the tail pipe. I had it running at cruising speed and then turned the key off at wide open throttle. Then I checked the plug. Don B.

[Rebel]

I think you probably do need to go down in size then, how well does it run?

[Rocketdog]

Those jet sizes really don't sound too large. #85-#35. Perhaps it's another problem that arose from having the carb apart? A miss behaving choke? Like Rebel said, how does it run? Does it start ok and idle well? Or do you smell fuel and see puffs of black smoke out the exhaust? Does the pilot screw have any affect what so ever when you adjust it? You might go down a size on the main but #34 to #35 is hardly anything on the pilot. If there's a problem at idle, I'd be willing to bet it's something else. Also, even if the problem cured itself miraculously, a short trip at WOT wouldn't clean a well fouled plug. It takes awhile to burn it off.

RD

[Rebel]

Going to a big bore you would think you would need more fuel and from what people have posted in the past, the jets you put in there are close to what you might need. I'm with RD, I'd leave the pilot alone and adjust the main jet. Put a few miles on it and see how it goes, running rich is not doing damage that running too lean would. You can also try dropping the needle to lean it out a little.

[zbuck]

Did not mean to take this long to reply. Had a death in the family and had to take of that. Have not had any time to work on the scooter, will have this week and will try your suggestions and post back. Don B.

[Rebel]

Sorry to hear about your loss.

[zbuck]

Thank you Rebel, still have not had time to work on the scooter. Everybody and his/her brother wants their go-kart engines freshen up and the latest tricks done to them. The carb I have does not have a ajustable needle. I guess I could try shims? Don B.

[Rebel]

Shims are an option if you can put them in.

[zbuck]

Finally some scooter time. I changed the main to a 78, the only other jet I have. Put in a new plug. Started pouring down rain and did not ride, will do today and then check the plug. I noticed that when I reved it up that black soot came out of the muffler. I think I may have a problem with the auto enrichner (new). Upon further checking I can not shim the needle. Don B.

[Rebel]

well black smoke does sound like a rich running scooter, could be that your auto-enricher is totally the culprit.

[zbuck]

Well after a ride yesterday, still black soot on plug. But the engine has good power thru full throttle. Where as with the 85 jet it would fall on it face about 3/4 throttle. Some where around here I have the information about removing the auto-enrichner and going to a primer system. Or could I put an off/on switch to disable it after a short warm up? Don B.

[Rebel]

are you sure the enricher moves or is it stuck in one position.

[zbuck]

Rebel, I took the enrichner off the carb, put 12 volts to it and extended about 3/16" after 5 min's. Should I have 12 volts to the hook up on the scooter for the enrichner? Thank you, Don B.