Best reliability questions for stock 139QMB ( ? )

[Ayyub Ansari]

Hello Everyone,
I am new to this forum as well as scooters. I was recently given a 2010 Peace Sports 49cc scooter with what I believe to be a 139QMB power plant. This unit is completely stock and it was given to me by a friend who was too large (240lbs) to get it to perform properly. The scooter had been sitting unused and unrun for about 8 months before I got it. The scooter starts easily and idles well, however when throttle is applied it studders and or dies and at WOT it will bog down then die. In doing research it appears that there may be a fuel delivery issue in regards to jet size as well as inefficient air delivery (I could have misunderstood though). The bogging happens wether it is being ridden or if it's on its stand and given throttle. I would like to give this to my daughter but it is necessary that it is reliable and able to perform up to 40-45mph.
Now for the question(s); I would like to know what would be the best recommendations for building this into a very reliable machine (if possible). Once again, this unit is currently completely stock. Would a bbk be the way to go, or just a better carb, cdi, plug, airbox etc. be a better way to go? Please let me know if there is any other information that I can provide to help you all suggest the best recommendations.
My daughter, who would be the sole rider weighs approx 127lbs if that helps. I am fairly mechanically inclined , but scooters are new to me so I lack experience with these engines. I'm not too concerned about costs however I'm not trying to purchase a whole new scooter 1 part at a time. I have found a mountain of information already but nothing that compiles everything into one clear thread (or if it was I had definately missed it/them).
I would like to thank everyone in advance for their input.

[doomsday]

Well to be perfectly honest your going to get the same answers for pretty much any chinese scooter.
Take the carb apart and clean it. (most likely its gummed up from the gas)
Adjust the valves
Go up to a bigger jet.
Changing roller weights in the cvt might add more power or a little more top end. (which if the previous owner had done that, it might have performed better for him)
Possibly adding a windshield might give ya an extra mph or 2, but at her size, maybe not.
Go through and do a PDI on the scooter, tighten every bolt down, replace the fuel and vac lines, etc...
After that, it starts getting more expensive.
Hopefully that will at least get you started in the right direction

You may have a secondary problem here to. Depending on your states 50cc law, your speed limit requirement may not fit within that law. Many states restrict 50cc scooters to anywhere from 25mph to 35mph and anything over that, the rider is required to have a motorcycle endorsement and tags/insurance on the scooter. So it might actually be better (depending on your states law) to actually get the endorsement and get her on a 125 or 150.

[Ayyub Ansari]

Thank you for the great advice. I will clean the carb and adjust valves and such this weekend. As far as up jetting is concerned. I have a question or two regarding sizing and brand recommendations if anyone could help me with that.

* What size of carb jet should I get (do I get only the primary jet or secondary as well (I think it has two). What brand and best place to purchase.

*What size roller weights should I get and brand. I assume that I want smaller weights for more top end, correct?

*Are there aftermarket carbs that can be recommended? I am looking for the best reliability that I can get from this scooter.

*Thoughs on aftermarket CDI, spark plug or other electrical components.

* One last question for this post; Is there any other nomenclature that I should be aware of when speaking about this motor beyone is being a 139QAB model motor?

I don't mind putting a few hundred into it to make sure my daughter can ride her scooter around town and not have to push it back home. ;D Any input, especially for brands and vendors would be appreciated. Thanks in advance.

[dadzilla]

As to size I'd avoid up-sizing unless you add a BBK in. A mild jet change is what you need. The NKG spark plug is a help, also consider a led taillight, saves on volts.

As to rollers it depends on two things, your weight and the roads, hills or flat that you deal with. Take one out, weigh it and try dropping 2 grams. However if your going in, consider upgrading the entire variator.

Er, buy her a good helmet, because eventually no matter how careful she is, everyone drops it eventually.

Lastly, if the tires look shabby buy some good rubber. I mounted a pair from Vee and the difference was notable on how much better they gripped the road. Good Luck.

[Ayyub Ansari]

I ordered a few NGK iridium plugs today (CR7HIX) as well as some fuel and vacuum lines by Helix. I am not sure of the quality of this brand but it was the only brand that I happened to find in my search. It was recommended that I consider a variator upgrade. Can anyone suggest a good manufacturer and/or model number for my application? I believe that I should also consider a mild jet upgrade but I am not sure what size would be considered a mild upgrade. Any advice would be much appreciated there as well. As far as terrain goes, the area that we live in is very flat with only a few small hills that would not be in the path of her normal daily riding so I am not sure what variator and or weights I should consider for this type of riding. Thanks in advance for any suggestions that you may have in regards to my questions. I can assure you that I am doing my best to resource these answers on my own, but I am hoping to rely on group expertise for the sake of reliability and safety for my daughter. We have now both enrolled in motorcycle safety class as well.

[Terri "Bunny" Lee]

now this is just me talking ok, i am NOT a mech.

get her running with a new carb or cleaned one 1st
your changing lines and plug so thats great.

but for any 50 cc to run , consistently, at 40-45 is a stretch
you would have to run WOT alot of the time which isnt great
( im gonna get alot of disagreement on that, but i just feel if you run it WOT all the time, your just slowly killing it)

is it 2 t or 4t ? 2 stroke or 4 stroke?

when you start upgrading the jet, you are gonna have to get into 'fine' tuning the a/f mixture and all that.
which isnt hard but just time consuming

also the same if you change the airbox, you'll have to play with upsizing the jet, etc etc

i dont buy alot pf parts i have over 8k miles on my 150
and everything is still basically stock also
but i deal mainly with greg @ mainly scooters
cause he is a great guy, will answers questions etc etc etc

heres a link to his shop
eshop.mainelyscooters.com/shop/

hope i gave any ideas

[stiv625]

Feb 20, 2013 20:01:45 GMT -5 Terri "Bunny" Lee said:

but for any 50 cc to run , consistently, at 40-45 is a stretch
you would have to run WOT alot of the time which isnt great
( im gonna get alot of disagreement on that, but i just feel if you run it WOT all the time, your just slowly killing it)

Couldn't agree more. I installed a 50mm BBK ("100cc" actual 83cc) just to avoid running mine WOT 98% of the time with everything tuned to the max for my driving needs. 40 mph was an adequate cruising speed but I was only pulling up the hills here at 24 mph. Now I run the stock intake, carb, CVT, exhaust, etc (just changed the carb jet) and I feel like it's as reliable as can be because I'm running WOT maybe 50-60% of the time as opposed to 98%. And I climb even the steepest hills at 35 mph easily.

I was in the top speed cruising range of 40-45 mph before on my 50cc but I had just about everything modified or tuned to the max and it just wasn't reliable. Had problems with cold starting, warm stalling, poor fuel economy, weird noises, etc etc. Even now with my 83cc BBK I try not to cruise over 40 mph too often because the tires, suspension, steering, braking, etc wasn't designed for it.

That being said, for the average person, I would just tune your carb and CVT and accept that you're going to be running WOT most of the time. I do believe these machines were built with that in mind. When it goes, it goes, some would say with the BBK I'm just speeding that process up.