150cc running problem

[yardog]

I have a 150cc jonway. Hard to start but it will start. Will not idle. Have to work throttle to keep running. It surges up and down with throttle in same position low rpm to high rpm. A few days ago I got it to idle after long warm up and adjusted air/fuel . But yesterday and today it will not idle at all. Have adjusted valve. It has 180 psi compression. It wants to backfire a little. Have put on new intake, fuel, fuel filter, fuel and vacuum hose. I bought it not running, seller said he put on new carb. Do I have bad carb, cdi, coil or other problems you might think of?

[scootnwinn]

Most likely a vacuum leak or other fuel air issue. Make sure it's all tight and not leaky. Do you know how to check for vac leaks?

[terrilee]

this is gonna silly as heck BUT
what kind of plug are u running?

id start there with a good NGK iridium plug
then start checking the other stuff

[scootnwinn]

Replacing the plug is always an inexpensive good first thing to do on a small engine

[tvnacman]

What size carb is on there ? How long has the new carb been on there with the scooter not running ? How old is the fuel ? What about the ignition parts are on there ? When it back fires is it from the muffler or the intake ?

Lets start with the above .

John

[yardog]

I replace plug with ngk. 24mm carb. new fuel. getting good blue spark on plug. seems like may be back firing from intake. not sure when carb was replaced, probably a couple months. scooter purchased new may 2012. previous say park one night and would not start next day,

[terrilee]

guys, correct me
isnt 180 a bit low
i thought over 200 was good

[tvnacman]

sounds lean , I would pull the carb off and open the bowl and clean the jets and passages . A valve adjustment would be a good idea . Spark is not the problem , is there a high proformance coil or cdi in it ?

John

[Lefty]

If the RPMS at IDLE are bounceing it is running really LEAN, you either have a AIR LEAK or the Carbs Fuel Mixture is way off.
So First check for any Air leaks take a Spray Bottle of Water and spray Indiviudal Areas, If the IDLE CHANGES you found a leak. Also check your Air Filter tubing for cracks and what not also you air box. If cracked tape them up etc..

If all that is good then adjust the Carbs Fuel Mixture
Lefty

Follow this procedure to tune the carb: Take your time 1/4 turn to much in either direction makes a big difference.


ADJUSTING YOUR FUEL RATIO MIXTURE:

YOU WANT THE HIGHEST RPMS OUT OF THE AIR RATIO MIXTURE SCREW:

Start your scoot and Get The Engine Nice and Hot about 5 minutes so that the Enricher IF it has one is no longer Allowing Extra Fuel to come in. Then do the following to fine tune the Fuel Ratio Mixture:

FUEL RATIO SCREW:

FIRST TRY RICHENNG THE FUEL MIXTURE FROM ITS CURRENT SETTING:


RICHEN THE FUEL RATIO MIXTURE:

1. Turn the Fuel Mixture Screw COUNTER CLOCKWISE 1/4 of a turn and wait 10 seconds to let the engine catch up with the new setting.
a. If the RPMS go up REPEAT #1 UNTIL the RPMS GO DOWN OR NO CHANGE(then go to b).
b. TURN the Fuel Ratio Mixture Screw CLOCKWISE 1/8 and that should be your highest Fuel Ratio Mixture setting—GO TO #3.

******If on the FIRST 1/4 TURN from the STARTING Position IN #1 ABOVE the RPMS GO DOWN OR NO CHANGE , turn the Fuel Ratio Mixture Screw Back the 1/4 turn to the Starting position and wait 10 seconds until the engine catches up -- GO TO #2 ******


LEAN THE FUEL RATIO MIXTURE:

2. Turn the Fuel Mixture Screw CLOCKWISE 1/4 of a turn and wait 10 seconds to let the engine catch up with the new setting.
a. If the RPMS go up REPEAT #2 UNTIL the RPMS GO DOWN OR NO CHANGE(then go to b).
b. TURN the Fuel Mixture Screw COUNTER CLOCKWISE 1/8 and that should be your highest Fuel Ratio Mixture setting—GO TO #3.



IF YOU GOT TO THIS POINT AND NOT INSTRUCTED TO GO TO #3 THAT MEANS THERE WAS NO CHANGE IN RPMS FROM DOING #1 or #2 ABOVE, IT IS TIME TO CLEAN THE CARB:

YOU NEED TO CLEAN YOUR PILOT JET AND PASSAGE AND AIR PASSAGES AND THEN START FROM #1 AGAIN.


IDLE SPEED SCREW:

The Idle Speed Screw on a Carb that are on most 4Ts you will find on the right side on the THROTTLE CONTROL WHEEL. It is the screw with a SPRING on it.

To Lower the IDLE you turn it COUNTER CLOCKWISE to Raise the IDLE you turn it CLOCKWISE.

3. If after adjusting your Fuel Ratio Mixture your idle is to fast Turn the IDLE SPEED SCREW COUNTER CLOCKWISE. For the 50s-150s they like to idle around 1500-1800rpms, for the 250s+ they like to idle from 1800-2000 rpms, pick the smoothest idle with the rear wheel not spinning ---GO TO #4.


TEST YOUR ADJUSTMENTS:

4. Now give the Throttle a QUICK twist and the RPMS should climb up quickly without hesitation or bogging and come down to where you set your Idle at---GO TO #5.

5. NOW take a ride and try it out, the Fuel Ratio mixture may need a tweak in either direction now that the motor has a load on it.

The tweak will be minor maybe a ¼ turn richer or leaner IF it acts up with a load---GO TO #6


6. When it acts up BACK OFF the throttle about ¼ of an INCH AND HOLD IT THERE:

a. If the motor speeds up it is LEAN you need to richen it up a little.

b. If the motor settles down and or stumbles and then settles down it is RICH you need to LEAN it out a little.

GO TO #5 AGAIN.



Problems with the IDLE:

1. Give the throttle a quick twist:

A. If the rpms drop below idle speed, then recovers (or stalls), it is RICH —Turn the Fuel Mixture Screw Clockwise ¼ turns at a time and go to #1.

B. If the rpms do not drop quickly to the idle speed but hang and drop slowly it is LEAN —Turn the Fuel Mixture Screw Counter Clockwise ¼ turns at a time and go to #1.

[yardog]

It won't run slow enough to adjust idle. Have adjusted valves .004 intake and .005 exhaust, Could petcock be sucking fuel into intake manifold? Plug looks like running rich. Stock cdi and coil.

[tvnacman]

recheck the valves , are the vac lines wet inside ?

Jhon

[Lefty]

Originally Posted by yardog

It won't run slow enough to adjust idle. Have adjusted valves .004 intake and .005 exhaust, Could petcock be sucking fuel into intake manifold? Plug looks like running rich. Stock cdi and coil.

Turn the IDLE SPEED Screw CLOCKWISE BEFORE you START IT, First try 1/16 if not 1/8 turn.
I am sure it stays running if you give it a little throttle.
Lefty

[yardog]

Took off petcock. Cranks and runs better but won't idle right. A/F does not have any effect on idle. Runs good @ 3000rpm but will die if turn down around 1500. It will be idling a 1500 and start to die and I can twist throttle and if will go up and stay @ 3000. Only vacuum line connected to manifold is line to de-accelerator. I have install new manifold but I sprayed starting fluid around manifold and had no effect on engine speed. Twist throttle hard an fast response to high rpm. I beginning to think carb is bad unless someone can think of anything else I have not done. Still hard to start keep running until warmed up then cranks good.

[jmstar09]

Sometimes a carb is beyond cleaning/repairing. I have had scooters come in that had sat for a while that didn't want to run correctly. Cleaned the carb 2 or 3 times with no change so finally I install a different carb and they run great.

I've bought several of these carbs in the past. They work fine and are a great price. I like them cause they have a mixture screw that isn't plugged off. The free fuel filters are crap but the carbs are good.

http://www.ebay.com/itm/GY6-150-CC-S...dc9c26&vxp=mtr

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[yardog]

Replace carburetor with new. Still have same problem. Cdi or coil? Could there be internal engine problem other than valve adjustment as I have adjusted and rechecked. Valves are ticking. It revs to high rpm without any hesitation. A/F mixture screw out about 2 round, can not get low enough idle to fine tune adjustment.