tuning a carb. help

[51cc]

so ok. using a pb 13, 14mm keihin carb. on a stock dio. clean carb, clean muffler with lye, 100 miles ago. 113 psi in the motor. service is 114. this is a chinese checker. dont know. little scratch on it. checked with two, mines lower than the other. maybe a little.
the jetting is 90 main i think. its fine. it runs fine at 90 main. at full throttle. startgin my scooter, its hard to start. you can't give it any gas. once you wait like 20 seconds, you can barely touch the gas, itll keep wanting to die. you have to barely touch it, and let it rev, until it starts revving and not choking or leaning and running out of fuel out, and not dying, and getit to rev full rev, then i can just take off. this is from cold start. its real hard to keep it from dying, as soon as you touch it it wants to die. the pilot is 42. with 45 it is past 2 1/2 turns out out the idle mixture screw. like at 3 or something. screw will unscrew itself at 3 or more. and the needle is at the leanest setting. i forget exactly whta it does but it wont run if the needle is made to run richer, by moving the clip up. oh yea i remembver, it wont take off. if i richen the pilot jet, it moves to 3+ turns out on idle. if thepilots leaned, i can't get the bike to rev fast, itll take off and just smoke, or not run, just like missing too much to go, but smoke pours out. i think. thats one thing that happens, bike will slowly go down the road smoking.

so is my jeting off? or do i not have my idle set right? or something, thats what i was thinking. asking. tire doesn't spin at idle. one time i had the idle off, couldnt get it to run, couldn't jet.

[stevo52]

Pull the head and spark plug off and check out the carbon build up. Alot of smoke is sign of running rich or poor combustion. A 90 main does sounds big... your scooter could have been running rich for awhile and now is finally fouling up enough to cause problems.

[vvtr]

The main jet may be ok depending on what air filter you have. There is no easy answer with jetting as every bike will be different.
I think it could be bogging at idle cos the idle is turned too high to start it.... They only need a whif of gas to start and idle, and small cc motors are very sensitive to idle mixture settings.
Youll just have to experiment.

I had trouble jetting mine with a 26mm slide carb but after a lot of meddling ot starts on the button and revs clean - now on a 218 main and 48 pilot lol

[51cc]

high idle is making my scooter to bog because to start it? im sort of fucked up, but i didnt understand that.

ok, so how do i tune idle? what rpms just to tune? should it be able to idle low? when i rev it, if im talking about my stock scooter, i dont know when exactly, but i seen a video, he revved it, and it just cut off. said it was uhm something wrong with the carb, jet. done that, but later on wasnt so bad. dint cut out so bad. it's a little hard to start.
should i be able to turn the idle to low and it still run good? then can i jet from there?

[51cc]

but as your lowerijng the rpms it gets leaner and richer.

[felliott]

If you use a stock air cleaner, #80 jet works very well.

[one1]

Had a similar issue with scootie before I sold him, and now again with a completely new carb after a week of running it. Trying to decide if the electronic choke went bad after only a week or if it is all the oil getting past the petcock and running through the carb while it is sitting and dropping into the gas bowl making it run oddly until it warms up. Similar situation to you....... cannot touch the throttle until the engine gets a LITTLE heat in it, then I have to feather it up and yank the throttle open or it'll stall. After I do that just ONE time it runs like a top. It didn't happen last week when I put the new carb on and waited until I had about 50 miles on the new carb to start doing it again like it used to with the old carb. I've had issues with oil and that petcock from the beginning with both carbs so I dunno if it is that or the choke, but a brand new carb cured it for a week.

Once it has been started for the day and has any heat in it it will start and run like a top, but I'm not sure if it isn't just fresh gas in the bowl and not gas that has been saturated by the oil run-off, if it can do that.

[51cc]

great it seems to be running lean. i can just mess with my throttle and kill it. its like my needle is lean. this is just the stock motor. so how does the needle jet work? is the thinner the end is if the rest is the same length, make a certain throttle position, richer or leaner? and what about the length, if it's shorter, like, shorter is supposed to be richer. longer is leaner.
what positions do the thichness and length control?
should i just use a manual choke?

[51cc]

i think the length controls if it's richer or not, and that's around 1/4 to 1/2 throttle i think.
and the fatness would control probably 1/8 to 1/4. hmm

[one1]

An interesting follow up to my issue that might give you some clues. I came out and my scooter was over on it's side (filter side). Oil from the 2 stroke reserve was everywhere and I had to clean up a huge mess. I expected it to be very hard to start since I had tried before to start it from being on it's side (fell over in the truck when the straps broke coming home the day I bought it). It actually fired right up and rode better than ever (this was yesterday) from a cold start. Today it did the same. It's definitely in the carb settings between the fuel and the oil so I'd forget about jetting and work on tuning.

Maybe yours will run better if you kick it over. ;D

[2strokd]

If it struggles to run, or bogs when given throttle when cold but is fine otherwise the idle/air mix is lean. Try turning the mix screw in a quarter turn at a time until its better. This may take a few cold starts to get right.?.

If it just wont rev nomatter the temp i would check the main jet. Could be plugged or too small?

[51cc]

it runs really good on the main. which is floored. just it can't rev up to get to the main jet. cause of inbetween jets. i was riding around. ive got it all took apart now. and i got some questions. about gasket material. ill get some pics. next post. and it does struggle to start. and once warmed up, it just starts or doesn't and you gotta play with the throttle. and when i was starting it, i revved it and when it was quitting, i covered the airbox hole. and it started running. but my pilot on 50cc's is 42 for a keihin. i dont know. never talked to anyone, its a 13 or 14mm carb. never talked to anyone about this scooter, and adjustable pilot jets, the scooter dont come with them. this is the dio carb, airbox intake set i got. ive went up and down on jets.
on needle clip. motor is 1psi under service limits.
so i adjust the air fuel mix screw, when im tuning, when the motors totally warmed up? like an hour or 2 later?

[51cc]

oh i pulled my head. ill get some pics, exhuast side, the piston is white, the boost port side, carbony. maybe an air leak? and i got some pics. so only a little bit of case gasket material got sucked in the motor thru the boost port when i had an airleak. i seen it. i just busted the case open. never done this before. it deosn't look like it had much gasket material on there anyway to begin with. how much do i put back on there? it looks like they put a couple of drops, here and there.

oh yea the spark plug looked like that too, one side white, other carbony.






notice, no gasket material hardly. i just pulled it off, doesn't seem like there was much gasket material to begin with. ? i mean, nothing else fell off. and see the piston, one side is clean, exhaust, and the other side is carbony. i mean, how can the stuff shoot thru my scooter, then get hot. the spark plug is the same, it's two different sides.

[90GTVert]

I coat the case sealing surfaces with a thin layer of ThreeBond on each half. Worked every time so far.

[51cc]

anybody know why my exhaust port was burnt up.
edit: that red in that one picture is just from the camera. haha. i think. it;s not on it. whateverm, no i dindt even get up. so ..... i scraped gasket material between each half off when i was cleaning it from the back. each half had like a curve, and would come around to the other side. more came out of the boost port, than is left on the sides. like whats left, is less. you dont see nothing left on the case halves, except for scrapes. the boost port was filled. like, big bunch. half full.
i said the boos tport was full of gasket material. i was wondering why i was having trouble jetting. i couldn't jet, the mid-throttle was screwed.