Anyone know much about 139qmbs?

[the0captain]

I picked up a stupid chinese scooter because it was cheap and i wanted to learn a little about the 4stroke 139qmb.

its a little hard to see it but i just layed the pieces back on to snap a quick pic.



so its called a "Quiet BM50QT-3" (*insert bevis and butthead laugh* QUIET BM *insert bevis and butthead laugh*) and I have googled my brains out and can not find another one. But the motor has 139QMB stamped on it so at least i know what that is. Now here is where I start to get even more confused, the belt cover says KTM


Not really a big deal that I don't know the year and make but I like to know what I have at least.

But after a valve adjustment, crab cleaning and a new spark plug it runs really well at least.

I forgot to take a picture but the clutch bell, clutch and driven pulley look like they might swap over to the elite. I haven't taken it all off to compare sizes but it looks larger. Potential upgrade for an elite? I will try and take it all back apart tonight to compare sizes and compatibility.

[Mystic]

i Wouldnt put any of that chinese stuff in my elite, it might catch something hahhaha not sure about the clutch but you can put the elite variator in the chinese one and hte clutch springs and clutch also not sure about the pully parts. I was thinking about getting a Geely for my sister it was cheap for 100 but decided against it. you can do just as many mods to these engines to give them some pep but is it 4 stroke?? I see KTM scooters for sale on CL all the time for a pretty good chunk of change

[sprite2011]

Chinese 4 stroke, dump it in the trash. Chinese 2 stroke maybe I will use it, only if its a GY6.

[the0captain]

Chinese 4 stroke, dump it in the trash. Chinese 2 stroke maybe I will use it, only if its a GY6.

GY6 is a 4 stroke

[sa50pr]

i always thought when someone said gy6 the engine they were talking about was the 139qmb 4 stroke i got one sittin in my garage now it came off a Chinese scooter that had trailing link forks like an elite but there disc never seen forks like this on one before

[the0captain]

i always thought when someone said gy6 the engine they were talking about was the 139qmb 4 stroke

they are... well, can be. 139qmb is the 49cc version GY6.

http://en.wikipedia.org/wiki/GY6_engine

[tru72]

i work on those on a daily basis.. best thing is to keep the oil clean. Thats the number one killer of crank bearings, same like a ruckus. Use a good quality synthetic. Keeping the valves adjust will also keep them from burning. They do need some attention, the china metal is really soft and as the valves pound away the pus the seat into the head. which causes it to become tight on all of them. Most the transmission pats are honda zx stuff, variator, rear pulley/clutch , standard dio rollers and springs. So you dio guys who see this and get excited. a word of warning, do no use these in your bikes. they are cheaply made and wear out really fast LOL, especially the rear pulley. Cheap upgrades are abundant on ebay and all over. Bore kits are decent and it does make the botton/mid way better but as for real speed your biggest restrictor is the gears. Your best and easiest upgrades would be replacing the center spring with a 1000rpm, and putting 5 grams rollers in it. Just those alone you will see a great over all improvement.
hope some of this helps you.. in a nut shell they are fun to play with but wear out really fast. The design is a good one, its a honda lol. the quality of the materials and tolerances are something else to be loved. if your looking to make it fast like a dio , then you should look elsewhere.
Any questions just pm me if anything
aloha
D

[Spreetard]

*double post...oops!*

[Spreetard]

Chinese 4 stroke, dump it in the trash. Chinese 2 stroke maybe I will use it, only if its a GY6.

Perhaps you should do your homework before trashing on peoples new toys.

The 139qmb is a lesser cousin of Honda, but it can make for a fun and pretty reliable bike that is cheap to work on, if not as simple as a 2stroke engine.

My cheap china bike is held together with zip ties, mud and good luck. That said, I've put thousands of trouble free miles on it. I haven't started it in weeks, but I'm willing to bet it would still start right up with no protest and run exactly like it always does. The problem with a lot of china bikes is the owners lack of any mechanical skill. There are definite quality control issues, but the major problems usually manifest within the first few thousand miles. And really, what do you expect from a vehicle that costs $600 new? So you have to iron out the mechanical wrinkles. And if you drive like an idiot, the body panels will break like eggshells when you crash. That's where the zip ties come in.

I'm sick and tired of all the people making chinabikes out to be worse than they are. Many a "junk" 139qmb is just in need of severe valve adjustment and some new roller weights. Those are the top 2 most common "problems" I've seen on them, and both are also commonly known as "routine maintenance". The rest of them need rebuilt because the moron owner didn't change the oil, and took out the bearings.

There are design problems occasionally, such as the completely overkill disk brakes on some of them that appear to be sourced from a full size motorcycle... My chinabike will lock up the front tire at almost any speed, but only if you slam on the front brake like a complete moron. That seems easy enough to work around... Don't drive like a moron, and don't loan your bike (cheapchina or otherwise) to any morons. Problem solved.

Also, like Tru wrote whilst I was penning my response, don't expect 100,000 miles out of the thing. They are not "junk" but you get what you pay for in the long run.

[the0captain]

Since it was cheap i figured, "why not". i've never done a valve adjustment before and it turned out to be alot easier that i thought it was going to be. she purrs like a kitten now instead of a chattering like a drunk squirrel. the rollers look good with no flat spots. however the center spring seems really really tight? i couldn't squeeze the belt into the rear pulley at all so i'm not even sure if its spreading. i haven't drove it on the road since i don't have a headlight bulb but from what i can tell it doesn't really feel like its going into the "next" gear.

also, the bikes odometer says it has 1.9 miles on it. yes, 00001.9 however, the gear in the wheel doesn't work and must have broke at ONLY 1.9 miles lol. Now THATS reliability!

[veedubh20]

Chinese own ussa

[swimmingfree]

the0captain

i
dont
no
about
you
L
O
L
swi
mmi
ngf
ree
lol

[Palero2003]

I actually have a spare motor 139qmb today actually swapped the clutch. the clutch fits the elite fine just have to use the elite nut. the variator I switched out awhile ago. the back part with the rollers in it only. my elite one was ate away. kepted my boss and the front part of variator. cover will not fit on with the other parts without spaceing the cover out washers or whatever. with the clutch didn't notice a real differance good or bad. does sound kind of cool around 5mph. def can't get the second part of cover on unless space and prolly file the inside. can grab a pic 2maro if ya want.

[maddog]

ahhh, slowly the gy6 engine is comming to this forum, you can work the balls off this engine but not a 4 stroke....

[Trafficjamz]

ahhh, slowly the gy6 engine is comming to this forum, you can work the balls off this engine but not a 4 stroke....

You make less sense everyday Not a four stroke?