139Qmb more power/top speed

[ruckclone]

OK so i bought a ruckus clone it wouldn't go over 25 30 it was getting to much air so i ghetto rigged a plug(pen cap) for a week or two while the jets came in the mail it got up to 40-42 unverified while waiting. so stock jet was 82 went to 85 now. got a new plug and performance coil also performance cdi. now it gets between 35 and 40 depending on wind conditions without the ghetto plug now. i was wondering what else i could do without a bbk. maybe a cam with exhaust. the way the air intake is set up now its like ramming cold air in while driving so i didn't want to do a uni filter because the colder the air the more power the engine makes at least on any other slightly bigger engine. i know i need to tune the weights but i haven't opened it up yet to see what size and the stock weights are. so besides that what else could i do.
If i do have to go bbk what size is best so the bearings dont stat to screw up on me i heard after a certain size i think 47 they do

[Rebel]

Welcome.

First go to our 50cc forum and open the thread labeled some thing like Threads that Should have been stickies, you will find a lot to chew on. I will ad another comment here in just a few minutes.

[terrilee]

HI & WELCOME
now im NOT a a mech but been around
heres thing that u can do, but the right combo. is the key
change your rollers to sliders
different weight--dang is it? down in weight to get more top end?
have to check that.
bigger variator
change the gears, taller or smaller, duh i forget
change the clutch springs
and all before a BBK
but your speeds are good, how fast do u want it to do?

[Rebel]

link to that thread;

scooterrebels.proboards.com/thread/328/all-threads-stickies

The most bang for your buck will be to get the variator set up for you and the way you want to ride, putting a performance one like a Dr Pully in there is not a bad idea. I would suggest going to a set of 4.5 or 5 gram rollers if you want to keep the original variator.

You can put on a performance head and that will help a lot but if I had the head off, the big bore kit is no trouble to put on. With either of those changes you will need a bigger jet to keep it from not running lean.

Here is a page with some performance parts for you to look at.

www.scrappydogscooters.com/139QMB_50cc_Performance.html

[ruckclone]

my town has roads that are 45 so all i need to go is 45 but im goin to school for building/machineing race engines. so i like to test the maexes of motors.
i work in a machine shop too. so im goin to do a valve job i heard .003 and .004 are perfect. then im porting a polishing the heads but if i do that do i want an exhaust?

[ruckclone]

ok rebel thanks. stock are 5 grams so should i go to 6 or 4. and i have an 85 jet stock. what bbk should i go for if i want the engine to last long like i said i heard they ruin the life of the motor. and if i port and polish i shouldnt need a performance head right? and is the variator gear bent outwards a little for the starter gear to release? mine i was looking and it is.

[ruckclone]

also lee thank you for the advice

[Rebel]

BBK is touchy, a 73cc that is usually called an 80cc is about what you want to go with. You might get to 45 without the big bore kit. Porting and polishing may be all you need along with the variator mods, a different spring in the clutch will only give you a different off the line feel, they set the RPMs that the clutch locks up at.

Get a new exhaust if you do the head I wouldn't spend the money unless that was done, it would look good but not give you much, just an opinion.

You have to remember the speed depends on RPM's power will get you there faster but if the motor is not turning over faster you won't go faster, unless you do something to change the final gear ration, changing to a performance variator gives you that new gear ratio because they are larger. Now if you do that you need to makes sure the belt is long enough to take advantage of the size.

[Rebel]

Bent? I don't have a 50 to look at and see but I think not.

[ruckclone]

yea like kicked outward kinda it looks weird im not sure if i did that or not and what size belt if i do that do you know?

[Rebel]

The belt you have may work fine, you need to take a sharpie and mark the running surface of the pulley and see how high the belt goes , it it erases it al you are good to go.

Stock belt is something like a 669-18-30, you need to get one that has a first number that is a few bigger The guys at parts for scooters could probably help you out there.

[ruckclone]

ok thank you and if i do go bbk can i just buy the piston and rings and bore the engine bore more at the machine shop i work at? because dont you use the stock parts of everything else?

[Rebel]

You could, but check out the prices it may not cost you any more for the complete kit. Also be care of how thin you bore the cylinder walls. A lot of the kits come with a cylinder skirt that is bigger than the stock and requires a case reaming to get it to slip into the opening. If you need to do that, the motor should really come off and apart so you can clean the shavings out.

[ruckclone]

yea then im just goin to bring the whole thing to the shop ive already decided ive been thinking about it. i need to port and polish so i have to disassemble anyways so i should just bring the whole thing it comes off in one piece. what size jet should i go if im in central fl and i already have an 85 in there nohing done except plug mire coil cdi and the rejet and thats it. and what all do i need to complete all that. i need the bbk, exhaust, and a jet kit do i need the free flow filter if i have the stock air box and it sticks out beyond the bike so its forcing cold air in? and thats it right?

[Rebel]

Mar 1, 2013 8:35:24 GMT -5 ruckclone said:

yea then im just goin to bring the whole thing to the shop ive already decided ive been thinking about it. i need to port and polish so i have to disassemble anyways so i should just bring the whole thing it comes off in one piece. what size jet should i go if im in central fl and i already have an 85 in there nohing done except plug mire coil cdi and the rejet and thats it. and what all do i need to complete all that. i need the bbk, exhaust, and a jet kit do i need the free flow filter if i have the stock air box and it sticks out beyond the bike so its forcing cold air in? and thats it right?

regarding the jet, sorry you will just have to try a few and get it figured out, i.t seems to be different for a lot of people.

I would either drill holes in your air box or use a uni filter either one, you are looking for performance and the intake needs opening up.

You will need a BBK that includes head gasket, valve cover gasket, base gasket, piston, rings, cylinder, wrist pin and clips, some will include a head as well, you will need a exhaust gasket, download a couple of the service manuals I have linked to here for the 139qmb.

You can pull the motor out and haul it down to your shop pretty easily. With it out you can bore the case if you need to.