Carb hard to adjust

[robert1c]

Hi Dawgs,

I have a Linhai 250B and i have been dealing with an issue of trying to adjust the carb.
i let it warm up and then try to set the idle to the point right before the rear tire starts to turn. if i leave it there it may be right about 1800rpm which is good but the issue is during a ride if i stop at a light sometimes it drops to about 1100rpm and tries to die. if i feather the throttle to 1500rpm it idles fine there but if i let it go it drops. the other issue is to get it there it idles at around 2200/2300rpm at cold start.

i have added a K&N air Filter and a straight though performance exhausts. the fuel mixture is at 2.5 turns out.

Any help at what i should be looking at would be appreciated.

Thanks!

[zfjelstad]

I've been dealing with about the same issue except I can't rev mine up past 4k rpms as well, but my idle is behaving the same as your's. Have you adjusted your valves yet? I have changed the fuel filter and all 3 vacuum lines. i'm going to change my fuel pump in the next couple of days as soon as it comes in the mail. I will let you know if that fixes it.

[inkyben]

I'd check the diaphram for any tears or leaks and look at the needle close to see if it has any marks or notches on it.

[zfjelstad]

Is the diaphragm you are referring to right in the top og the carb? What should I do if there are mark's or notches on the needle?

[inkyben]

Yes its at the top of the carb, held in by two screws. Once you loosen the last screw it'll wanna pop off since theres a big spring underneath but its easy to put back in so dont worry.
The diaphram will be the entire rubber assembly inside and in the center will be the needle. Check around the rubber diaphram for any tears or cracking and the needle is attached to it but just hold it against a light and see if theres any notches on it. If there are which isnt too uncommon then it'll need to be replaced.

[zfjelstad]

Okay, we're all good. I went out again and messed with my mixture screw again after checking the diaphram and what not, and tightened the mixture screw all the way down. Then I loosened the mixture screw out maybe a quarter turn, and now the scooter is running beautifully. I have no need to change out the fuel pump now. Or do I? Any explanation for this? At least I'm happy my scooter is running swell now. I even took it out for a joy ride with my wife tonight for the first time since I bought it used back in April.