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Post by 12string on Jul 23, 2012 15:56:18 GMT -5
Ok, I have the carb back together and the scoot is running great but I want to make sure that I have the mixture settings correct. The carb has only one adjustment to it, I assume that it is the air fuel mixture. Right now I have the screw adjusted 3 full turns out, if I turn it in the idle increases, if I continue to turn it in the RPM's continue to clime until it is running really fast. I have adjusted the screw out until the idle slow and even if I open it more it does not affect the idle. Have I adjusted this correctly, I don't have much experience with 2 strokes.
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Post by 12string on Jul 24, 2012 16:52:57 GMT -5
No one knows if I did the carb tune correctly?
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Post by OverReved on Jul 24, 2012 17:13:52 GMT -5
I never saw your post yesterday .
The screw you found is most probably the idle adjustment screw. It has no effect on the air to fuel ratio.
when you turn the screw in the idle rises as you said. When you turn this screw out the idle lowers as you said. If you turn this screw out enough it will have no effect on the idle because it is no longer in contact with the throttle arm which moves the throttle plate, as you said.
If your bike is running fine I'd do nothing more than set the idle to the specified RPM using this screw which is often found on a plate or sticker on the bike.
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Post by wile on Jul 24, 2012 17:15:10 GMT -5
You should have another screw to adjust JUST THE IDLE. But you do want to get the HIGHEST IDLE from the AIR FUEL MIXTURE then lower the IDLE using the IDLE SPEED SCREW which there should be something on the carb just for that purpose.
Can you take a picture of your carb.
Wile
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Post by OverReved on Jul 24, 2012 17:20:11 GMT -5
I don't think it would be a good idea to attempt to adjust this carb if there is not a problem with the bike to begin with. If there is a problem it may be posted in a different thread but I'm not going to search for it. If it ain't broke why fix it. the scoot is running great |
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Post by wile on Jul 24, 2012 17:27:30 GMT -5
He asked if he adjusted it correctly and if he turns it in Richening the mixture and the rpms climb that means the motor is running on the lean side. He can get a little more power out of the motor if the mixture is adjusted better.
But your right if it is running good why mess with it, I would just be concerned with the lean motor.
Wile
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Post by OverReved on Jul 24, 2012 17:29:45 GMT -5
Then suggest to him that he should read the plug instead of bunking around in his carb and how to do it properly. It's a simpler and accurate way to determine what is happening in the running engine.
The screw he described was the idle adjustment screw when I read it. not the idle mixture screw. His is probably still hidden and may need to stay that way.
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Post by wile on Jul 24, 2012 17:53:43 GMT -5
He mentioned the Air Ratio screw, but he could be turning the IDLE SPEED screw.
That is why I asked for a picture of his carb it all depends on what type of carb is on there. If its a Slider Carb they ususally have a screw in the center of the carb which is the IDLE SPEED Screw that raises or lowers the Slide.
If there is a Screw to the RIGHT of it toward the Air Filter that is an AIR RATIO Mixture screw, turning that Clockwise richens the mixture(all it is doing is cutting out some air) and Counter clockwise Leans the mixture allows more air.
If there is a Screw on the Left side toward the Intake then that is a FUEL RATIO Mixture screw and Turning that Clockwise Leans it and Counter CLockwise richens it.
If he has a CVK carb then the Idle speed screw is on the Throttle Control pulley and the Fuel Ratio is on the side of the Intake Manifold. Turning that Clockwise Leans it and Counter Clockwise richens it.
Wile
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Post by 12string on Jul 24, 2012 18:50:20 GMT -5
The throttle cable is attached directly to a needle valve in the carb. The throttle cable pulls the needle out opening the only jet in the carb, there is no low speed or high speed jet only the one. There is no butterfly valve as in a traditional carb no regulation of the air supply it is wide openThe screw that I speak of is the only adjustment on the carb.I believe it is the idle adjustment screw. There are 2 adjuster nuts on the throttle cable, one is a lock nut the other lengthens or shortens the cable length. I can't take a good pic as the carb is back on the scoot and all the tupperware is back on blocking a good shot of the carb. The carb appears to be very simple in design.
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Post by wile on Jul 24, 2012 19:06:22 GMT -5
Ok so you have a SLider type carb and if the screw you are turning is OFF CENTER Close to the AIR FILTER SIDE it is a AIR RATIO mixture and if there is NO OTHER SCREW then the idle is controlled by the Two screws on the throttle cable hooked up to the Slide. Raising the Cable raises the idle and lower it lowers the idle.
Wile
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Post by wile on Jul 24, 2012 19:21:28 GMT -5
What motor do you have I tried to find a carb like yours WITHOUT the Center Idle Speed screw but all the ones I found have the IDLE SPEED screw in the center of the Carb.
Wile
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Post by 12string on Jul 24, 2012 19:25:55 GMT -5
not sure what engine I have it is made in Taiwan made by a company called MZ, the model is a Moskito I am sure it is a 50 cc. It is fairly old a 2002 model with only 2700 kilometers on it. I will go and look for a serial # on the engine. I found a plate that says CPI Motor corp. with a serial # that I can't quite read. I did find a very small brass adjustment screw next to the one bigger adjustment screw. the pic of the bigger screw is on my privious post too, I took the carb apart because the engine was quitting intermittently , I found a small gob of something in the jet The other is the pug in the bottom of the float bowl.  |
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Post by wile on Jul 24, 2012 19:39:12 GMT -5
Cool, but to lower the IDLE loosen up the LOCK nut on the Cable and then the other will raise or lower the slide to lower your idle.
Loosen the LOCK so it is a few threads away from the bottom nut.
Then adjust your AIR RATIO to get the highest IDLE then back it off just a little about 1/8 turn. Then lower the IDLE unscrewing the bottom nut to where the rear wheel is not spinning and you like the idle then tighten the lock nut down.
Wile
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Post by 12string on Jul 24, 2012 19:43:06 GMT -5
so which is the air ratio, the real little one or the bigger one?
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Post by wile on Jul 24, 2012 19:57:11 GMT -5
Where did those two screws come from?? I thought you said your carb only had one screw on the outside? But on a 2 stroke like yours with a slider the one with the spring is the IDLE SPEED SCREW and THAT IS NORMALLY FOUND in the center of the carb to get at the SLIDE from the outside, the other is the AIR RATIO screw. Wile  |
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Post by 12string on Jul 24, 2012 20:01:19 GMT -5
thats just like mine! thanks for your patience.  The other screw was on the back side of the bottom of the float bowl. If for pic was my carb you could not see it it would be on the other side of the carb down on the float bowl. |
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Post by wile on Jul 24, 2012 20:11:00 GMT -5
GREAT!! So do not mess with the NUTS ON THE CABLE GOING into the Carb.
The Big screw with the knorled end you turn the Clockwise to Raise the Idle and Counter Clockwise to lower the IDLE.
Well you see the SCREW ALL THE WAY AT THE BOTTOM of the bowl that is your Carb bowl Drain screw. You unscrew that a little you don't have to take it out and there should be a hose attached to a connector near it so you can drain the gas out of the bowl. The hose hangs down pointing to the ground.
Wile
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Post by 12string on Jul 24, 2012 20:24:34 GMT -5
Thanks Wile, you have been great help!
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Post by wile on Jul 24, 2012 20:25:13 GMT -5
Good luck man and ride safe
Wile
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The other screw was on the back side of the bottom of the float bowl. If for pic was my carb you could not see it it would be on the other side of the carb down on the float bowl.