Should I buy this electric fuel pump?  By  jjoshua20213 (Read 2,304 times)

If your tank is above the carb no need for an electric pump as gravity works fine . It is common to have a fuel pecock go bad and hurt top RPMs . If you have the tank in the floorboard many opt to use a vacuum Mikuni fuel pump instead of electric .

If it is stock the come jetting lean so a larger main jet often fixes this issue .

Would help to know the make , model and engine size .

from my own experience this is not really a good idea. i tried it, and it was overflowing my carb. if you decide to install it you also need to install a pressure regulator.

I do not believe your running out of gas in the carb bowl, what I suggest is try a bigger main jet, I think your running really lean when you run it at WOT for a stretch.
Alleyoop

Have you tried to connect fuel line directly to the tank, and leave the gas cap off?

not true. When my jonway was brand new, i suffered the same symptoms, it drove me nuts.Then one time it happened, For some reason, I decided to open the tank to check fuel level. I left it1/2 way closed, and noticed that it didn't happen again. I looked on some other scooter forums, and saw a thread about the same thing. It said drill a small hole so i did and problem solved. It could be a venting issue in another area of the system, but who cares? letting a little more air into the tank works fine.
also its a well known fact that at wide open throttle in any engine (even in cars),manifold vacuum significantly drops. this is a common problem in scooters. From the description of his problem, This is exactly what it is. Not jetting. he already tried that.If the manufacturers did everything right, this forum would serve no purpose ;D

Have to say your main problem really is the 24mm Carb. To get a 24mm carb to work right on a 50 is a lot of trial and error and anything wrong will cause problems. The 24 sucks in a lot more air than what the carb you should have on it. You do realize that the 150cc scoots come with a 24mm carb right. Also the Intake on the head is most likely smaller than the 24mm intake to except the 24mm carb. So what you have is lip which now effects the flow of fuel and air going down into the motor.

People think let me pour a gallon of gas down this little motor and I will have 900hp, doesn't work that way.

But to get the best advice on getting your 50 to perform right and not burn it up is PM MILLSC, he has done many BBKS and knows what works and what doesn't work.
Alleyoop

Wow you use an MJ with a 24mm carb ? If the head is not ported and has larger valves plus a performance exhaust it is too big of a carb . Do you use the spacer ? I used a MJ on my 50mm BBK with stock carb . Your not creating enough vacuum to utilize a 24mm carb . Sure a size up carb or MJ makes one run better but too big it will not perform as good . Example a buddy had a Gran Torino with a 351 Cleveland that had a 2 barrel carb . He bought and Edelbrock 4BL intake and a Holley 650 double pumper on a stock engine . If he had the heads worked , performance cam and exhaust yes it may have worked great . It made more vacuum sound that it performed . I got it to take it back and get a 600 CFM Edelebrock carb that I bolted on out of the box and it was amazingly way better for his set up .

If you compare drinking with a straw vs a 1/2 inch piece of pipe you can see that bigger does not mean better all of the time

Check out the head at the top of this page www.scrappydogscooters.com/139QMB_50cc_Performance.html


You can always go with EFI if you have the cabbage www.ecotrons.com