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Post by tfletchnh91 on Jun 20, 2011 11:47:33 GMT -5
Hey guys just picked up a 2008 50cc scooter with the 139qmb motor. haha like most i need that little extra speed out of the scooter and hate slowing down on hills. Looking at ordering a 100cc big bore kit (yes the stroke is only around 85ccc). Looking to use my stock carb (as long as i can get it tuned running good) And also remove air box and install a open air filter.
Has anyone installed this kit and got it running good?
What Size Jets(Main And Pilot, Needle Setting)?
What Size Variator Weights?
I only care to get around 50-55mph tops, I weigh 160lbs
I just want to be able to get there quickly and go up hills without slowing down as much
Any helps or tips would be great thanks
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Post by elusiveone on Jun 20, 2011 14:53:03 GMT -5
Hey guys just picked up a 2008 50cc scooter with the 139qmb motor. haha like most i need that little extra speed out of the scooter and hate slowing down on hills. Looking at ordering a 100cc big bore kit (yes the stroke is only around 85ccc). Looking to use my stock carb (as long as i can get it tuned running good) And also remove air box and install a open air filter. Has anyone installed this kit and got it running good? What Size Jets(Main And Pilot, Needle Setting)? What Size Variator Weights? I only care to get around 50-55mph tops, I weigh 160lbs I just want to be able to get there quickly and go up hills without slowing down as much Any helps or tips would be great thanks Buy a 150cc, Cause you are not going to get 50-55mph on the scooter. And even if you do somehow manage to get those speeds (And you will not with a BBK alone) You will blow the engine in 2 months tops. These 139QMB engines are built stock to withstand 72cc. I believe the top speed with a BBk on a 139qmb 4T engine is around 51mph and the person that has reached that speed has: Performance Clutch New Contra & Torque springs Performance Variator (Using sliders not rollers) 72 or 81.3cc BBK (not sure which, kinda forgot) Upgear Transmission Performance exhaust and a few other things These crank in these 139QMB engines are not built to handle the torque and stress of the BBK and will give way after some time (depending on how you ride) Most everyone goes with the 72cc kit from Enviromoto, as it seems to be the best bang for your buck. As far as jetting, needle placement, and carb tuning goes. Each scooter is different and will require a different setup. It is up to you to get it tuned right and running to your liking. My Suggestion is go with the 72cc kit, from what I have read they last a hell of a lot longer than the 81.3cc (100cc) kits and some even say they give more power (But not sure about this yet) Variator weights? using the new kit is going to push your RPM's higher than they were with the stock setup. I would recommend you start with 8gram weights and see how it runs, Especially after you install the kit cause you will want to keep your revs low so you dont tear the crank out on the break-in period. After the break-in you may want to drop to a 7gram or something, but once again it depends on your preferences and how you ride. i just installed that same (100cc) kit on my 1P39QMB and it runs great but I am having problems with metal shavings in the oil already, and my kit has less than 60 miles on it. And I have yet to open it up and see what it can/will do. Good luck to you though and I hope this helps on some insight for what you seek. P.S. There is a saying around here that you will learn to respect. "The faster they go, the faster they blow" |
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Post by cyberbeer65 on Jun 20, 2011 20:10:25 GMT -5
I have the Scrappy 50mm BBK and big valve head. 3000 miles and no metal shavings.
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Post by tfletchnh91 on Jun 20, 2011 22:18:11 GMT -5
Well i dont want to buy a new one. Got a wicked good deal on this one. Im going to go with the 100cc big bore kit, if i have shavings well oh well then i will deal with it when it happens.
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Post by meitianman on Jun 21, 2011 9:59:32 GMT -5
with a basically 139qmb 80cc scooter and home mods "drilled exhaust etc" i can get 45mph on fairly flat roads with 2 people "300lbs give or take" i cant see getting to much more without dropping some real coin to do so.
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Post by tfletchnh91 on Jun 21, 2011 11:06:37 GMT -5
ok guys i dont care about getting 50-55 mph. Lets get back to my main question. I am going to install 100cc big bore kit, and some clutch weights. I already drilled out my exhaust and put on a after market open air filter.
Has anyone istalled this big bore and got it tuned fairly close? Im just looking for somewhere to start with the jets with stock carb and big bore.
Looks like i should try the 7gram weights?
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Post by meitianman on Jun 21, 2011 13:43:56 GMT -5
i think my kit came with 7gram weights, i drilled the exhaust. i forget what jet came with it, it was a kit from enviromoto.com pretty sure it was a 90 main jet. i tried the stock 5gram weights but was not happy with the performance, jeremy advised me that the bigger bore changed the torque curve and suggested i use the 7gram with the kit. been quite happy with it with those so i would start there.
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Post by tfletchnh91 on Jun 21, 2011 15:29:03 GMT -5
Ok thanks . Yeah thats what i was thinking. Are you using the stock air box or a after market one?
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Post by tfletchnh91 on Jun 21, 2011 15:36:16 GMT -5
And did you only change your main jet? or did you change your pilot and needle setting too?
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Post by larbro65 on Jun 22, 2011 15:12:08 GMT -5
i have fitted many 100cc big bore kits to 50cc 139qmb & have done lots of trial & error to get what i think is the best results .
remove original air cleaner & fit sports filter
fit No. 88 main jet in carby.
remove exhaust & modify & make outlet bigger.( i paid for exhaust shop to do it )
remove & replace variator rollers with 5 gram units
fit sports CDI unit with rev/speed limiter removed.
this is the best bang for low bucks .
you can put on big port heads etc but then where do you stop because then you have to fit bigger carby / sports cam etc & it really won't make that much difference for a daily runner.
if you are gonna start doing all that you may as well throw it in the bin & buy a 150cc.
some people just expect way too much out of a 50cc & just keep throwing money at something that is just not going to happen
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Post by tfletchnh91 on Jun 22, 2011 21:02:09 GMT -5
ok thanks. how about pilot jet and needle setting?
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Post by meitianman on Jun 22, 2011 21:02:21 GMT -5
i used the uni air filter that came with my kit and i did not change the idle jet. its got a stupid amount of miles on it now and despite some ugly noises its starting to make it keeps going.
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Post by larbro65 on Jun 23, 2011 0:52:05 GMT -5
you should not need to touch pilot jet . as regards to needle setting i would leave it alone & check spark plug after riding around to see if it is running rich or lean & go from there .
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Post by tfletchnh91 on Jun 23, 2011 17:47:56 GMT -5
Alright thanks guys
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Post by tfletchnh91 on Jun 24, 2011 11:50:17 GMT -5
So i decided to purchase the head with the big bore. I ordered the 100cc kit comes with all gaskets and valve already installed.
Does this change what i should run for a main jet and clutch roller weights?
Before when i was just thinking of ordering the 100cc kit without head i was planning on running 88 main jet and still was unsure of weights to go with.
Suggestions on weights is still welcome. I have been told to run 5 and been told 7 so im not sure what would be best.
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Post by tfletchnh91 on Jun 24, 2011 12:05:49 GMT -5
i have fitted many 100cc big bore kits to 50cc 139qmb & have done lots of trial & error to get what i think is the best results . remove original air cleaner & fit sports filter fit No. 88 main jet in carby. remove exhaust & modify & make outlet bigger.( i paid for exhaust shop to do it ) remove & replace variator rollers with 5 gram units fit sports CDI unit with rev/speed limiter removed. this is the best bang for low bucks . you can put on big port heads etc but then where do you stop because then you have to fit bigger carby / sports cam etc & it really won't make that much difference for a daily runner. if you are gonna start doing all that you may as well throw it in the bin & buy a 150cc. some people just expect way too much out of a 50cc & just keep throwing money at something that is just not going to happen Is this also installed with the big bore head or stock head? |
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