Jonway YY250T engine stalls By daviddahan (Read 3,015 times)

[Alleyoop]

Aug 15, 2014 12:35:29 GMT -6 daviddahan said:

BTW I noticed one thing if I move the adjusters to the right the RPM's go higher it that expected?

Regards,

David

That is what you want higher rpms when adjusted, right now the exhaust is loose so it is not opening all the way to let the exhaust out.
Then you can lower the idle using the IDLE SPEED SCREW that is the screw with the SPRING under it turning it counter clockwise lowers the idle.

So I would adjust the valves where you get the highest rpms.
Alleyoop

[daviddahan]

I need to try that. I just run the scooter until it got really hot and then took it for a ride.
after 1/2 mile it died.

I will try your suggestion and do the test again.

Regards,

David

[Alleyoop]

Yea if they are not adjusted right the motor will get hotter than it should. Did the fan come on to cool it down?
Alleyoop

[daviddahan]

It did. I am waiting for it to cool so I can try and restart it. Then I will let get hot and try the adjustments again.

Regards,

David.

[Alleyoop]

Great! do want the fan to come on otherwise we have other problems
Alleyoop

[daviddahan]

I did the adjustments again.
I made sure that I don't hear the tapping and tighten the bolts.

Engine was hot around half the gauge which on a regular ride it never gets there but when standing with no air flow I am expecting it to be bit hotter.

Then I did the adjustments.

Questions:

1. is it the right process or I am suppose to just warm it up?
2. is there anything else that can cause this?

After the adjustment I could rave the engine to more than 6000 rpm's and it didn't not die but I need to take it for a ride to really test it. I just had enough of pushing it back to my garage every-time it dies on me. I am afraid to take it to a long ride since then I need to call a tow truck to bring it back home.

I was looking for the fuel/air screw on the carb but couldn't find it. I think that this carb have it in a very inconvenient location which I can't reach.

One note about the engine when I raise the rpm's and then release the throttle it makes noise like water babbling in a sink when it's needs air like boope boope ....

Any idea? is it normal?

Regards,

David

[racerx125]

you mean pop as in something banging the insides of you exhaust when you decelerate usually means unburned gas gets in the exhaust and the heat in the exhaust ignites it and pop! pop! pop! my motorcycle does that too but never really cared, supposedly it ruins you exhaust valve but that what I heard. My valve has not failed doing those pops, for now. Alley knows the rule when popping and backfiring he could tell you, as I forgot what it meant. He posted it somewhere in this forum

[daviddahan]

No it is just making a pop sound. no metallic for sure.

It might be because of wrong gas air mixture from what I read but I can't find the location of that adjusting screw on my carb.

You can see the carb in the video I posted on this thread.

Regards,

David

[racerx125]

not metallic sound its more like exploding ballons

[Alleyoop]

Popping on DE-Celeration coming down to IDLE means it is to LEAN not enough fuel at IDLE which would also cause harder starting.

So yes you need to RICHEN up the FUEL RATIO MIXTURE, turn it 1/2 turn COUNTER CLOCKWISE.
here is your carb and where the fuel ratio mixture is, which if there is a PITA to get at.
Alleyoop

[racerx125]

doesn't it also mean you could have an exhaust air leak from engine to exhaust?

[Alleyoop]

No racer, if you had an air leak by the flange where it attachs to the motor it would backfire not pop.
The popping is caused by the sudden closing of the butterfly and cutting off to many of the tiny pilot jet fuel outlets or it is running a little LEAN to begin with. Or very rarely the ACV valve is clogged and not allowing extra fuel to flow on the de-cel.
If your idle is to low you can adjust the Idle which all your really doing is moving the butterfly open a little more(just as if you hold the throttle a little open does the same thing) and exposing more of the pilot jets fuel outlets thereby allowing more fuel to be sucked out.
Alleyoop

[daviddahan]

I had to remove the carb to do the adjustments. I can't do the tuning following the instructions you posted in the past since I don't have access to that screw when the carb is installed.

I notice one change since the adjustment when releasing the throttle the rpm goes down slowly and not as fast as before. I run the scooter a few time back and fort on my road about 1/2 mile each direction after the engine was hot. It didn't die yet. I am hoping for best.

I tried to re-produce the issue but couldn't.

Will keep you posted.

I for sure learned a lot trying to fix this issue.

Regards,

David

[Alleyoop]

If the rpms do not drop quickly to the idle speed but hang and drop slowly it is still to LEAN —Turn the Fuel Mixture Screw Counter Clockwise 1/4 turn at a time and on the center stand give the throttle a quick twist and see if that is enough if not do another 1/4 counter clockwise turn etc..

You can get this to get at the Fuel Ratio Screw or just make one up out of a piece of thin bar metal smash the tip to a flat and then put a bend 90% bend on it.
Alleyoop

[daviddahan]

I have that tool I bought it from one of your recommendations but I don't see how to access that screw since it is between the engine head and the carb.

I will try to give it a try.

Regards,

David