Building a Sport Scoot and I need help getting some more gas

[PremierScooters]

Hello everyone, I am building a demo 4 stroke 50cc performance scooter for my showroom. So far I have installed a MRP 47mm (72cc) Cylinder Kit with large valve head, MRP racing exhaust system, Uni Air Filter, Dr. Pully 6 gr. Sliders, a #95 main jet. The problem is I am still running really lean, I think I need somewhere around a #100-#105 main jet but the #95 (and a rip off at 9.00 each) was the biggest I could find for a 50cc carb. I have an idea to use the intake manifold and the carb for a 150cc scooter since I have every size jet imaginable for that size carb. I belive the manifold should just bolt right up, or I could get a performance intake from MRP. Has anyone had a problem like this before? Or could anyone give me any suggestions. I will pic up the intake and carb tomorrow to give it a try. I am at 55 mph on flat ground right now but would like to get to 60. I will be posting some pictures soon.

[katoranger]

All I can say is try it. The 150cc carb may be too large and cause it to bog.

Allen

[PremierScooters]

The 150 carb did not work, the 150 intake bolted right on but I think there is too big of a diffrence in size from the opening in the manifold to the opening in the cylinder head. I couldn't even get the thing to start up with the 150 carb. With the 50cc carb with a 95 jet the scooter flys, the speedo say over 55mph on flat ground which is probably around 50 but when I pull the plug the insulator is pure white and the motor is really hot. I wish I could find a bigger jet for the 50cc carb. MRP doesn't have them, partsforscooters.com has only up to 85 and scootertronics only has up to 95 and that's what's in it now. Maybe I will have to put the stock airbox back on. that might balance it out but slow it down a little. I guess it's better than burinig up a new motor.

[forchetto]

You could carefully drill one of your main jets up to the size you think it'll need using a small drill, some lubricant, and proceeding slowly and with a well-supported jet in a machine vice.

The jets are measured in mm, so a 100 jet will be 1.00 mm in diameter. 110 jet 1.10 mm and so on.

[PremierScooters]

Yeah the idea to drill a jet has been in the back of my head but I wasn't sure if I could drill one accurately enough. Well my Girlfriend works at a nut, bolt and tool supplier so I checked with her to see if they had any small mm drill bits. They had one pack of two 1mm drill bits for $1.88. I screwed the jet that I was drilling into a bad carb to hold it, put a few drops of oil on it and very carefully drilled it out with the drill bit on my dremmel with the long flexible extension. It worked out perfectly, now when I pull my plug the insulator has a nice light off white color to it instead of a pure white color. Thanks for the info! I just need to find some more small drill bits.

I will post some pics of this scooter soon.

I am trying to figure out a way to get a little more speed out of it right now it is running 50 on flat ground, 55 slightly down hill and 45 slightly uphill. So far I have installed:
MRP 47mm (72cc) Cylinder and Head
MRP Racing exhaust
6gr Dr. Pulley Sliders
Uni Air Filter
100 main Jet
MRP Racing Coil

[katoranger]

For 50cc 4stroke its doing pretty good.

Allen

[bdavison]

50 on the flats is pretty good for a 4 stroke, thats all Ive ever been able to get out of one, without changing the gearing.

I dont know if your scoot tranny is a CVT, or if its actually a gearbox. If its a gearbox, you can start playing around with sprocket/pinion sizes. But this is a sacrifice one for the other sort of thing. You either sacrifice acceleration for top end speed, or vise versa.

[phil]

dont be mislead there are diffrent gears on the 139qmb 60 isnt a problem i have done it but i used a 82cc kit but i dont give the extra speed to the size i bult 2 last week 1 ran out at the 45-50 mph range 1 just started running at that speed i would look for gears i didnt write down what the gears were but it was on a American Lifan scoot that had the higher gear there is on thing once you hit 60............i dont know how you get to 70 and im not sure you can on a qmb139