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Idling problem! SB50P
Posted: Sat Jun 25, 2011 6:11 pm
by gookies
The problem is that my scooter idles nicely only when the air screw is all the way in. It still idles when I adjust it, but as soon as I give it throttle, it dies out. It is getting gas, I have clear Tygon hoses now and just replaced the petcock. Air filter is intact and oiled. I'm guessing it might be the pilot jet?
Re: Idling problem! SB50P
Posted: Sat Jun 25, 2011 10:53 pm
by Bear45-70
You have a vacuum leak making your idle too lean. When you adjust your mixture screw to the factory spec you are way to lean. FYI, the factory spec number of turns is a STARTING place not a final adjustment. You adjust the mixture screw for the HIGHEST RPM possible, then adjust the idle speed until the rear wheel does not rotate.

Don't just look up some number read what it says to do!
Re: Idling problem! SB50P
Posted: Sat Jun 25, 2011 11:21 pm
by gookies
I know what the manual says for the air screw is where to start it off from and yes, I kept adjusting it 1/4 a turn trying to get it to the highest RPM, then I adjusted the throttle stop screw until the rear wheel barely moves (I can basically stop it with my pinky finger). It's just that when I adjust it like that, I give it throttle and it dies. You said it's a vacuum leak. I'm not sure where it could be coming from. I changed my vacuum hose and the bolts connecting the carb to the manifold are secured. The air filter box has its lid tightly secured and the O-clamp screwed in securely to the carb.
Re: Idling problem! SB50P
Posted: Sat Jun 25, 2011 11:26 pm
by Bear45-70
gookies wrote:I know what the manual says for the air screw is where to start it off from and yes, I kept adjusting it 1/4 a turn trying to get it to the highest RPM, then I adjusted the throttle stop screw until the rear wheel barely moves (I can basically stop it with my pinky finger). It's just that when I adjust it like that, I give it throttle and it dies. You said it's a vacuum leak. I'm not sure where it could be coming from. I changed my vacuum hose and the bolts connecting the carb to the manifold are secured. The air filter box has its lid tightly secured and the O-clamp screwed in securely to the carb.
A vacuum leak has to be at the carb or in the intake. Gaskets bad at the reed valves?
Re: Idling problem! SB50P
Posted: Sat Jun 25, 2011 11:29 pm
by gookies
Gaskets looked fine, a little dusty, but intact. I also checked the reed valves and compared them to the wiki page to see if it was good or bad. They turned out to be good. Also, by screwing in the air screw all the way in, that makes it so I'm running lean?
Re: Idling problem! SB50P
Posted: Sun Jun 26, 2011 12:08 am
by Bear45-70
You can not look at an assembled unit and tell if the gaskets are good or bad. You disassemble and replace them. Well at least we know why your engine doesn't run right, you assume facts not in evidence.
Re: Idling problem! SB50P
Posted: Sun Jun 26, 2011 12:36 am
by gookies
Er, if I just told you I checked the reed valves, you should know that I had to dissemble it to take a look, which means I dissembled everything that was relating to the reed valves.
Re: Idling problem! SB50P
Posted: Sun Jun 26, 2011 12:47 am
by Bear45-70
gookies wrote:Er, if I just told you I checked the reed valves, you should know that I had to dissemble it to take a look, which means I dissembled everything that was relating to the reed valves.
New gaskets?
Re: Idling problem! SB50P
Posted: Tue Jun 28, 2011 9:01 pm
by blaster716
Im having the same problem with mine , I rebuilt the carb , new reeds , and gaskets , new fuel line and vacume line, new plug ,new air filter , air cleaner is on tight . When it is cold it takes off pretty quick , but once it warms up it falls on its face when I try to take off.
Re: Idling problem! SB50P
Posted: Tue Jun 28, 2011 9:04 pm
by Bear45-70
Adjust the idle mixture per the instructions in the service manual. And if you say I set it to the number of turns it says, I will SCREAM!
Re: Idling problem! SB50P
Posted: Wed Jun 29, 2011 7:13 am
by blaster716
I adjusted the screw out till i got the highest rpm then adjusted the idle down till the tire stops moving.
Please don`t scream.
Re: Idling problem! SB50P
Posted: Wed Jun 29, 2011 9:37 am
by Bear45-70
blaster716 wrote:I adjusted the screw out till i got the highest rpm then adjusted the idle down till the tire stops moving.
Please don`t scream.
I don't have to scream, you actually adjusted it instead of just setting to a number in the manual.