New scoot left me stranded By rsw1158 (Read 806 times)

[rsw1158]

I have a new Jonway YY250T 244cc scooter, vertical engine. It is about 2 months old and just turned over 2000 miles. It has been running great until Friday on my way to work. I was about 7 miles into my 24 mile commute and the engine started acting like it was starving for fuel. It eventually bogged down to an idle with no throttle response then stalled and would not start. I tried starting it a few times but would not start. It even backfired a few times while trying to start. I left the scooter and had my wife take me to work. I got a ride back to my scoot after worked and it started up after a few burps and rode back like there was nothing wrong. I took the carb off and tore it down inspected and cleaned it with carb cleaner but is was very clean. Didn't see any dirt or debree to be concerned about. I reinstalled and test drove. It would only act up at full throttle. Again, it felt like it was starved for fuel. I ended up adjusting the valves and replacing the fuel pump. Mikuni DF52T. I also replaced the fuel filter, fuel lines, and vacuum hoses. I made sure I didn't have any vacuum leaks or air leaks. It still wants to act up at full throttle. It will start slowing down or bogging down like it isn't getting fuel. After I back off the throttle it will clear up and let me continue on at about 3/4 throttle. When it is at full throttle I noticed it won't ever tach out past 6K. Could the CDI be giving me grief? Any and all help will be appreciated.

[Alleyoop]

You need to adjust the Fuel Ratio Screw it is running lean. With the COOLER Temp changes it needs more fuel.
Turn the Fuel Ratio Screw Counter Clockwise about 1 full turn and give that a shot.
Alleyoop

[rsw1158]

Funny you mentioned that. When I went through the carb I also rejetted it because I felt it was lean. I went from a 38 slow to a 40 and a 120 main to a 130. It ran stronger but still acted up but didn't stall. It should be plenty rich by now you would think. The fuel air adjustment screw was non responsive before I rejetted and now I turn it about 1/4 turn out from flat to reach max rpm. After that, it will slow down. If I completely turn in flat, it will not stall but just slow down a little. This is my set up other than the rejetting. I removed my air box and installed a foam free flow air filter onto the oem air box air snorkel. Removed the carbon canister and vented my crankcase with a pvc valve and filter. Any thoughts?

[rsw1158]

The wild goose chase is on. I went through everything fuel and vacuum wise to make sure it was not a lean or rich problem causing this cutting out issue. I even went as far as to put the scoot back 100% stock as I bought it. I even filled the air box snorkel with water to check for air leaks and went around the air box and made sure there was no air leaks there before installing the air box. I even drained the carb and gas tank and put new gas in it to eliminate bad gas if that was the problem. It still does it. It will start acting up not before I get to 55 to 60mph when I am accelerating to go faster. It will let me cruse at 55 with no problem. After that, it's a gamble. Since it started acting up, I have replaced all the fuel and vacuum lines and a new fuel pump. Also adjusted the valves. What else could cause this problem?

[Alleyoop]

Also try Cracking the GAS CAP to allow more venting it may be building to much pressure and not allowing enough gas to fill the carb.

If that does not work, bring it up to where it STARTS to act up and BACK OFF the throttle 1/4 of an INCH and HOLD IT THERE.

Now PAY ATTENTION to what the motor does:
A. Does it speed up
B. Does it just settle down.
Alleyoop

[rsw1158]

I did notice something about the gas tank pressure I forgot about until you just mentioned it. It builds up a lot of pressure. The hose that comes off the tank and goes to the canister is a vent isn't it? When I was putting things together tonight and draining the tank, I tried to blow and suck on that line and nothing happens. I couldn't blow through it and I couldn't draw through it. I did have the cap off when I did this. Is this normal or is it plugged?

[rsw1158]

Also, when I do get this up to speed to where it acts up and back off a little, the motor does not speed up or settle down. It will bring its self to a mere idle then straighten its self up.

[Alleyoop]

I would try cracking the Gas Cap open. Those Vents for the tank if you fill it to the top with gas with the scoot bouncing around gas gets into the Vent hose and plugs it up.

Are you saying once it acts up it drops down to IDLE and THEN IT SPEEDS UP AGAIN?
Alleyoop

[Alleyoop]

Disconnect the the GAS TANK VENT hose at the CANISTER take the gas cap off and blow into it see if it is plugged up. If not I would take the hose put a fuel filter on the end of it and tie it higher than the tank anyplace. Then you can take the Canister and disconnect the hose going to the Air TUbe or air box and plug the connector up on the AIR BOX or TUBING and take the canister off and PLUG UP the VACUUM HOSE AT ITS ORIGIN.
Alleyoop

[kz1000st]

Did you overfill the gas tank? It sounds like you have a charcoal canister on your tank vent. If they get filled with gas they don't breathe anymore.

[fwd60]

I owned two of the 244cc chinese scoots the CDI caused both of them to run like that.replaced both CDS's and it ended the problem.used the CDI's on a hond Helix and a Elite neither would go faster than 53 mph.changed back to Honda CDI's and both ran 72 mph as always.

[rsw1158]

Alleyoop, thanks. And everyone else. It was the tank vent plugged. I cracked the gas cap and it is happy days again. I will try and find a vented cap and solve this problem once and forever.

[Alleyoop]

FANTASTIC!! Easy fix, those vent canisters and all that cause nothing but problems, take that stuff off. You do not need a new gas cap just drill a 1/16 hole through the top of the GAS CAP. Drill it through the RAISED part where you grab it to turn it.
Alleyoop

[rsw1158]

I did have it off and I will take it back off since I know the problem wasn't caused by the mods I made on my scooter. I think that I am going to leave the oem air box on though because I had to rejet my carb with a whopping 135 main jet and a 42 slow jet just to get it to richen up enough to match the amount of air being injested using the free flow foam air filter. It runs very strong like that but I am sure fuel consumption would be an issue.