scooter balks past idle. By rms59 (Read 661 times)

[rms59]

Hi,

I have a clean 125cc Chinese scooter that starts and idles fine but low rpm. As soon as I advance throttle it balks and dies. After it warms up for several minutes (at least 5) It runs fine but the idle is much higher.

I installed a new carburetor but the same problem exists. This is what I've done so far...

1. Fresh gasoline.

2. New Carb.

3. New vacuum lines

4. Checked valve clearances (cold) which were .004 on both intake and exhaust valve.

5. New plug gapped at .025

6. Checked compression (cold) and get 165 pounds.

7. Sprayed ether on intake manifold to check for leaks....no change in idle.

8. New air filter.

9. Disconnected automatic choke.

Any help or idea would be welcome.

Richard.

[Bashan]

I would check your auto choke to see if it is working. Remove it and hook it up to any 12v power source, a battery will do, and see if the plunger comes out about 3/16" in five minutes. Rich

[rms59]

Apr 28, 2014 19:16:32 GMT -6 Bashan said:

I would check your auto choke to see if it is working. Remove it and hook it up to any 12v power source, a battery will do, and see if the plunger comes out about 3/16" in five minutes. Rich

I'm going to check it anyway but I was under the assumption that since I have the autochoke unplugged that it would be in it's enriched state which should help the hard start.

I can only get the scooter to start if I block the intake with my hand and wait for it to warm up before advancing throttle.

Richard

[kz1000st]

There must still be something going on with your enrichener circuit. It runs fine when warm, you start it with a choke method by using your hand which rules out a vacuum leak. I would reconnect the choke and see what happens. It might be stuck.

[rms59]

Apr 29, 2014 8:46:51 GMT -6 kz1000st said:

There must still be something going on with your enrichener circuit. It runs fine when warm, you start it with a choke method by using your hand which rules out a vacuum leak. I would reconnect the choke and see what happens. It might be stuck.

It's more like me that's stuck.

I put it back together and still have the same cold start problem. After several attempts it will finally start with a very low idle and any advance of the throttle will stall it. If I initially set the idle higher it won't start at all. It's definitely starving for fuel because blocking off the air intake or firing a shot of ether allows it to throttle right up.

This is a brand new carb that came with a new choke installed and it does exactly what the old carb and choke did. Once it's good and warmed up it runs fine.

I need to somehow get more fuel to it when cold. (It's 52 degrees here)

Richard

[Alleyoop]

Do you have the AIR FILTER On? Have you adjusted the Carbs Fuel Mixture? Turn it clockwise until it stops and COUNT the number of turns it took to stop. Then turn it back Counter Clockwise the same amount of turns it took to close and ADD 1 more full turn and see if that helps.
Alleyoop

[Alleyoop]

Are you saying you have the ENRICHER unplugged and it runs fine after it warms up? If so then your Fuel Ratio Mixture is not allowing fuel to be sucked out or very little.


Do you have the AIR FILTER On? Have you adjusted the Carbs Fuel Mixture? Turn it clockwise until it stops and COUNT the number of turns it took to stop. Then turn it back Counter Clockwise the same amount of turns it took to close and ADD 1 more full turn and see if that helps.

Tell me the number of turns it took the Fuel Ratio Screw to close.
Alleyoop

[rms59]

Apr 29, 2014 19:54:22 GMT -6 Alleyoop said:

Are you saying you have the ENRICHER unplugged and it runs fine after it warms up? If so then your Fuel Ratio Mixture is not allowing fuel to be sucked out or very little.


Do you have the AIR FILTER On? Have you adjusted the Carbs Fuel Mixture? Turn it clockwise until it stops and COUNT the number of turns it took to stop. Then turn it back Counter Clockwise the same amount of turns it took to close and ADD 1 more full turn and see if that helps.

Tell me the number of turns it took the Fuel Ratio Screw to close.
Alleyoop 

The Enricher is unplugged, the airbox and air filter are on, and the mixture screw is a full 4 turns out. This is where it seemed to like to be when warmed up and on low idle. Again, the only way it started was to hold my hand over the air filter effectively choking it and would stall repeatedly if I advanced the throttle....I shut if off and let it sit for about 5 hours. The temperature is 45 degrees and raining today so it quickly cooled off. Then, on a whim, I turned the mixture screw out another two turns making it 6 full turns out and flush with the body of the carb. This time the engine started normally and after a minute I was able to advance the throttle.I have to leave so I'll test it again tonight to see if it will idle well when warmed up with the enricher plugged in.

[Alleyoop]

WOW!! It was 4 turns out and it took another 2 turns out for a total of 6. What that says is that the PILOT JET is to small and or the ENRICHER is bad and is EXTENDED out and is not feeding extra fuel for cold starts. Now here is the thing the ENRICHER has THREE ports 1 to get fuel from the carb bowl, 2 one to send fuel to intake, 3 to get air from the Air Intake side. Now it could be anyone of those are clogged and the ENRICHER is working but either no fuel is being sucked out or not enough.
I would take the carb off and get a Can of Carb Cleaner they come with a thin long straw and I would spray into every hole you see on the carb. And Spraying into a hole you should see spray coming out from someplace else.

Now you have to be careful having the Fuel Ratio Screw out 6 turns because the spring now does not have a lot of pressure on the screw and it could vibrate Loose and fall out. If your going to run it like that Put some silicone on the screw so it does not vibrate loose and fall out on you. But I something is not right and I would FIRST clean out and clear out all the passages to make sure a passage is not clogged and if it still does the same thing then I would get a #35 PILOT JET and put that in there.

Alleyoop

[rms59]

Apr 30, 2014 13:16:26 GMT -6 Alleyoop said:

WOW!! It was 4 turns out and it took another 2 turns out for a total of 6. What that says is that the PILOT JET is to small and or the ENRICHER is bad and is EXTENDED out and is not feeding extra fuel for cold starts. Now here is the thing the ENRICHER has THREE ports 1 to get fuel from the carb bowl, 2 one to send fuel to intake, 3 to get air from the Air Intake side. Now it could be anyone of those are clogged and the ENRICHER is working but either no fuel is being sucked out or not enough.
I would take the carb off and get a Can of Carb Cleaner they come with a thin long straw and I would spray into every hole you see on the carb. And Spraying into a hole you should see spray coming out from someplace else.

Now you have to be careful having the Fuel Ratio Screw out 6 turns because the spring now does not have a lot of pressure on the screw and it could vibrate Loose and fall out. If your going to run it like that Put some silicone on the screw so it does not vibrate loose and fall out on you. But I something is not right and I would FIRST clean out and clear out all the passages to make sure a passage is not clogged and if it still does the same thing then I would get a #35 PILOT JET and put that in there. 

I want to say thank you for the replies. This is a brand new carburetor (not used) but I will take it out anyway and check those holes tomorrow. I can't give it a test run yet because I had to take it apart just to check the valves but I started it again tonight (still 42 degrees in the garage) with the screw still 6 turns out and it started with no problem. I waited about 30 seconds and advanced the throttle with no bogging down at all. 

However, after I let it warm up about 10 minutes (this time with the choke connected) the idle didn't seem right until I turned the mixture back to 4 out. The idle came up higher and smoothed out doing that.

In other words.... It needs 6 out to start and 4 out to run. That #35 pilot jet seems like a good idea. I will report back tomorrow after cleaning those holes... BTW.. those photos look exactly like my carb.

Thanks

Richard

[Alleyoop]

Yes I think that will do it.
Alleyoop

[rms59]

Apr 30, 2014 20:43:39 GMT -6 Alleyoop said:

Yes I think that will do it.
Alleyoop

Alleyoop...... Last night I took the pilot jet out and although it looked clean (it's a new carb) I used an airgun and blew out all the holes. At first it looked like there was nothing in the center but using a strong light I was able to see the ungodly small hole. I also blew out the ports you showed in your image and every other hole/port I could find.  Then I put everything back together and it started fine with just 4 turns out on the mixture screw. 52 degrees outside.

This morning (62 degrees) I started it up, let it idle for a few seconds, then advanced the throttle and it didn't balk at all. I left the choke disconnected and took it for a ride. What a difference in performance between the old carb and new carb. No more surging or sluggishness. It ran smooth.

I came back, reconnected the choke, and went for another ride. Upon returning, the idle was lower but no stalling. I think I will leave it that way for now.

Thanks for the help and advice. There may have been something in that pilot jet after all but I blew every port jet out just in case.

Thanks again for the help and replies.

Richard.

[Alleyoop]

FANTASTIC!! GOOD JOB yea those are some tiny holes and any little speck of a particle will give you grieve that is why it is very important to have a good Fuel Filter Between the Carb and the Fuel Pump or Petcock.
Alleyoop