Idle speed question By jburd (Read 2,657 times)

[jburd]

So if some of you have seem my posts over the last couple months, you would know my JCL MP250a scooter has been out of commission for a little while. It's a long story that I won't tell here. Long story short I got everything back running and have had my scooter out on the road quite a bit the last several days. It's seems to be running great. I have noticed however that my idle is running at about 3000 rpm's. When I sit at a light I can feel a slight jerking forward like it wants to take off. It seems to me that before it broke down, the idle usually ran around 2000 rpm's but it's been awhile so I'm not certain. During the process of fixing it I did do a valve adjustment so I was wondering if that would possibly affect the idle speed. Does anyone have any idea about this and if the idle is too hight, is it easy to fix? Sorry if this is redundant and answered somewhere else. I couldn't find any post that answered this.

[alleyoop]

Yes your correct the idle should be around 1800-2000 rpms, at 3000 rpms or close to that the REAR WHEEL IS SPINNING. On the center stand the REAR WHEEL SHOULD NOT SPIN, set the IDLE to just when it wants to turn or a little lower if you have a tach set it around 1800-2000 wherever it IDLES the smoothest and REAR WHEEL NOT SPINNING.


LOWERING THE IDLE is easy LOOK at the CARB and you should see a SCREW usually with a KNOB on it usually BLACK to raise the IDLE you turn it CLOCKWISE to LOWER the IDLE you turn it COUNTER CLOCKWISE. If you cannot find it TAKE A PICTURE LOOKING DOWN at your Carb and put the PICTURE up and I will label where the IDLE SPEED SCREW is for you.
Alleyoop

[richardthescooter3]

Here you go Just below rubber hose.

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[jburd]

This morning it started fine but when I gave it gas it died. Then it wouldn't start at all. I haven't adjusted it yet. It acts like it wants to start but almost acts like it can't get enough fuel or the fuel air mixture isn't right. Any ideas?

[alleyoop]

Yep, the idle speed screw is on top of the Throttle Control Wheel, it has a spring on it.

For it not taking throttle, check you Air Filter and for any air leaks around the carb. Get a Spray bottle with water and start it up and spray individual areas around the carb looking for Air Leaks. If you spray a certain place and the IDLE changes on you you found a leak. Also check your intake manifold for cracks, they crack because the carb is not supported on the Back end and it bounces and cracks the rubber part of the intake manifold.

If all is good no leaks then now you will need to adjust the fuel ratio screw. First turn it clockwise until it stops then turn it out 2 1/2 turns(THAT IS A GOOD STARTING POINT) from there you can fine tune it to get the HIGHEST IDLE AFTER THE MOTOR WARMS up at least 5 minutes idleing to give the ENRICHER time to shut off the extra fuel for cold starts.
Alleyoop
Here is how to go about adjusting your fuel ratio mixture:

First Start up the Scoot and let it warm up At Least 5 minutes so the ENRICHER cuts off the Extra Fuel.

YOU WANT TO GET THE HIGHEST IDLE OUT OF THE FUEL RATIO MIXTURE:


So from where it is currently set FIRST TRY richening it up more:

1. Turn it 1/4 turn Counter Clockwise and wait about 10 seconds to allow the motor to catch up with the new setting. LISTEN or look at your tach:
a. If the IDLE GOES UP REPEAT #1, UNTIL the IDLE does not change or drops a little THEN TURN THE SCREW CLOCKWISE 1/8 and that should be the highest IDLE from the Fuel Ratio Mixture and go to #3.

**** IF ON THE FIRST 1/4 TURN COUNTER CLOCKWISE THE IDLE GOES DOWN OR DOES NOTHING, TURN IT CLOCKWISE 1/4 TURN TO GET IT BACK TO WHERE IT WAS AND GO TO #2****

2. Turn it 1/4 turn Clockwise and wait about 10 seconds to allow the motor to catch up with the new setting. LISTEN or look at your tach:
a. If the IDLE GOES UP REPEAT #2, UNTIL the IDLE does not change or drops a little THEN TURN THE SCREW COUNTER CLOCKWISE 1/8 and that should be the highest IDLE from the Fuel Ratio Mixture and go to #3.

3. If the idle is TO HIGH NOW LOWER the IDLE USING the IDLE SPEED SCREW so that your REAR WHEEL JUST WANTS TO TURN... Go to #4.

4. Now give the Throttle a quick twist and let go, the Motor should Rev up nice with no sputtering or hesitation and come back down to where you set the idle.

*** IF TURNING THE FUEL RATIO SCREW Clockwise or Counter Clockwise DOES NOTHING Then the Pilot Jet AND OR ITS PASSAGE ARE Clogged and you will have to clean the Jet and CLEAR OUT THE PASSAGE. And go through the Procedure again***

[jburd]

I haven't yet gotten it to start. I pulled the fuel line out of the carburetor and turned it over. Fuel pulses out of the tube so I am assuming my fuel pump is OK. I've looked at my fuel filter and it doesn't seem plugged. Any ideas? It will crank up at first then turns off and then just cranks. If I leave it set, then it will fire again but shut off immediately. I'm really getting frustrated with this thing. I'm feeling like I got a lemon. I hear great stories from others but I seriously can't keep this thing on the road. It's always something.

[alleyoop]

Have you adjusted your valves?
Try this see if it help acts better:
Turn the FUEL RATIO SCREW clockwise until it stops then turn it out 2 1/2 turns(THAT IS A GOOD STARTING POINT) from there you can fine tune it to get the HIGHEST IDLE AFTER THE MOTOR WARMS up at least 5 minutes idleing to give the ENRICHER time to shut off the extra fuel for cold starts.

It sure acts like a fuel problem, when you go to start it open and hold the throttle a little open and see if that gets it going and idleing.

I am suspecting the Pilot Jet and Passages are Clogged and are not allowing fuel to be sucked in. You most likely will have to take the carb off and clean it out.
Alleyoop

[jburd]

I thought it might be the valves. I had adjusted them earlier but with it being my first time, thought I could have not quite gotten them right. It did seem to idle really high after adjusting them. I just checked them and did adjust the lower side a little. It did seem too loose. It didn't solve the problem but I think it will help in the long run. I did notice that if I hold the throttle open when trying to start, it cranks faster but just won't start. I will try the fuel ratio screw. I will keep you posted. Thanks for the help. Very much appreciated.

[richardthescooter3]

jburd, listen to Alleyoop he is right If I was try to adjust the fuel ratio screw first, and then if that don't work you can take the carb off. (Don't give up) I had a lot of trouble with my scoot also, but now it fires right up, but it did take some adjusting to get it there

What did you set the valves at?

[jburd]

I'm not exactly sure which is the fuel ratio screw. Is it the the one alleyoop described above with black knob on it. It kind of looked like something like that on the bottom of mine but wasn't able to turn it. I wasn't real sure from the picture above. I have attached a picture of my carburetor. Can you point out which is the fuel ratio screw.

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[jburd]

Here's a pic from the other side.

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[alleyoop]

Cool, I copied your pictures and labled and pointed to where the FUEL RATIO SCREW is and where the IDLE SPEED SCREW is.
Alleyoop

Fuel Ratio Screw is UNDERNEATH the Carb near where it attaches to the Intake Manifold: MANIFOLD.



IDLE SPEED SCREW is on the back of the Control Wheel:

[jburd]

Thanks alleyoop! The fuel ration screw didn't seem to want to turn at all. I will work on it more tomorrow and keep you posted. Thanks again for the advice.

[terrilee]

jburd
you said u did a valve adjust. ?
were u on TDC???

just asking

[jburd]

Terrilee, the first time I did it, I'm not sure I was. It did run after that though. When I just redid it, I'm pretty sure I was. I hand turned the engine 3 times until I got both the line on the chain pulley and the line on the other side (next to the oil stick) perfectly lined up. Once I got both sides lined up, the gap on the exhaust side seemed too wide as there was a lot of play in it with the gap tool inserted. I adjusted it down a couple of turns.