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Just bought my first scooter about a week ago. Is labeled JSD250T-2 but after reading the forum it appears to be a yy250t with a 244 Helix clone motor.







I test drove the Scoot before buying it and it performed beautifully around town. However when i went on back country roads i find that i have a top speed of 50-55mph before the Scoot starts to pull back, if i let off the throttle it responds normally up to 50mph then starts to loose power again. Also, if i ride at over 45mph for an extended period of time it backfires on deceleration. Seems as though it is running lean so... there is either a vacuum leak prior to the fuel pump or the tank is not venting well enough?


I took all of the plastics off of the scoot and found that the vac line to the carb had no hose clamp on it which may be the cause of the issue!?! But...I figure while i have it apart its probablly a good idea to replace all the vac and fuel lines anyway . I hear the the vac lines are 3/16ths and the fuel lines are 1/4? I plan to take a small section up to the auto parts store to verify. I have a few questions about replacing the lines however and thought you guys will probably be a great resource... def better than the trial and error method.




To replace the vac lines i plan on starting from the intake manifold to a Y connector, right side of the Y to the carb, left to the fuel pump. The current vac line to the fuel pump appears to have an additional T connector halfway down going to the evap canister, can i remove this T and extra line all the way to the canister and block it off there or is this line needed? These are the only vac lines I am seeing and should be the only ones needed to operate normally correct?








As far as fuel lines go. There is a vent line from the top of the tank leading to a circular valve that outputs to the evap canister. This valve is around mid gas tank so I wanted to move it to above and wanted to know if the additional line to the evap canister is necessary or if it can be removed then plugged at the canister as well so i have space to relocate the vent valve? The gas line from the bottom of the tank goes to a small filter, I plan replacing this while doing the lines, then to the fuel pump. Then from the fuel pump to the carb bowl. Just to confirm that is really all there is to it?



Sorry if these questions seem a bit obvious but this is my first vehicle with a carb. so I don't want to screw anything up.

I do have a few electrical gremlins as well, the running tail light does not light up though the brake and turn signal lights do. Also there does not appear to be a blocking diode at all on the charging system? I do get 12.8v plus while the motor is idling and about the same at 5k rpm so i am not too worried about this just yet. But i figure these will be a different post down the road after i get the fuel starvation/vacuum issues worked out.