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4 stroke 50cc to 100cc big bore on a QMB139

 
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bigbore15379



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PostPosted: Sun Mar 20, 2011 7:31 pm    Post subject: 4 stroke 50cc to 100cc big bore on a QMB139 Reply with quote

Hey everyone I just last week bought a 05 qingqi 50cc 4 stroke scooter. I know nothing special but it was $100 from a friend. I want to put a bigbore kit on it and was wondering if you guys could help me. First off I found a place near me on ebay that sells a 100cc bigbore kit and it says its for my motor. heres the listing: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=330459445932


I know some of the bigbore kits on ebay come with upgraded coil packs, would I need this? also what size fuel jet would you reccomend using? and where could I order it from? I plan on just removing the whole airbox and just putting a filter right on the carb. is there gonna be a cooling issue with this major displacement upgrade? any other mods I have to do for this to work? thanks a lot any input is appreciated


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azza



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PostPosted: Sun Mar 20, 2011 8:06 pm    Post subject: Reply with quote

some info here about main jets but only up to 80cc:
http://chinesescoots.forumwise.com/chinesescoots-thread6237.html



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bigbore15379



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PostPosted: Sun Mar 20, 2011 10:54 pm    Post subject: Reply with quote

thanks, another thing, would I need to change the clutching?


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Scootin
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PostPosted: Mon Mar 21, 2011 12:04 am    Post subject: Reply with quote

Yes! If your plan is to go faster. The 100cc kit will produce lots more power, but it can't capitalize on that power without a gear up kit.

If you just want faster acceleration, then no. Smile



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bigbore15379



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PostPosted: Mon Mar 21, 2011 3:43 am    Post subject: Reply with quote

yeah I figured as much, I just dont yet understand how the clutching/gearing works on these things. I'd like to be able to do 55-60 on it if possible without spending too much.


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JDi



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PostPosted: Mon Mar 21, 2011 12:28 pm    Post subject: Reply with quote

bigbore15379 wrote:
yeah I figured as much, I just dont yet understand how the clutching/gearing works on these things. I'd like to be able to do 55-60 on it if possible without spending too much.


Why did you buy a 50 that tops out at 40mph if you want to go 60mph? I don't understand why you didn't buy a 125? Either accept the 50 goes as fast as it goes, or sell it on and buy a 125. Don't waste your money trying to make a little bike perform like a big one.



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Yellow Scooter



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PostPosted: Mon Mar 21, 2011 4:30 pm    Post subject: Reply with quote

Why not do a crate engine swap for a PE50 90cc motor. Then the trans & geartrain will be optimized for the extra engine size. It'll be cheaper & easier than to try & bore the utter crap out of the little 49cc then watch it overheat, with that 49cc carb, exhaust, & drivetrain.
Ideally with this level of motor, a 17mm or 19mm carb would run this motor like it should, without tuning difficulty. Add an expansion pipe exhaust, and the scoot should be good for a cruising speed of 50-ish, and 60mph topout.



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bigbore15379



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PostPosted: Mon Mar 21, 2011 7:02 pm    Post subject: Reply with quote

JDi wrote:
bigbore15379 wrote:
yeah I figured as much, I just dont yet understand how the clutching/gearing works on these things. I'd like to be able to do 55-60 on it if possible without spending too much.


Why did you buy a 50 that tops out at 40mph if you want to go 60mph? I don't understand why you didn't buy a 125? Either accept the 50 goes as fast as it goes, or sell it on and buy a 125. Don't waste your money trying to make a little bike perform like a big one.


I bought this in a box of parts for $100, thats why I didnt buy a 125. The bigbore I just put on my snowmobile this year costed $3200, so when I saw I can get one for this thing for well under $100 I figured itd be well worth it. I think I might just stick the unlimited rev cdi in and throw the bigbore. I dont use it for extended trips or anything I have a real bike for the highways I just use this to mess around town and the gf rides it around


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bigbore15379



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PostPosted: Mon Mar 21, 2011 7:09 pm    Post subject: Reply with quote

Yellow Scooter wrote:
Why not do a crate engine swap for a PE50 90cc motor. Then the trans & geartrain will be optimized for the extra engine size. It'll be cheaper & easier than to try & bore the utter crap out of the little 49cc then watch it overheat, with that 49cc carb, exhaust, & drivetrain.
Ideally with this level of motor, a 17mm or 19mm carb would run this motor like it should, without tuning difficulty. Add an expansion pipe exhaust, and the scoot should be good for a cruising speed of 50-ish, and 60mph topout.


where can I find this motor? I did some looking around but came up with nothing but a pe50 90cc bigbore kit. How much are they?


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Yellow Scooter



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PostPosted: Tue Mar 22, 2011 4:36 pm    Post subject: Reply with quote

http://www.partsforscooters.com/90cc-2-stroke-1PE40QMB-Engine
There it is. The whole shooting match.
It'll have more actual cc's than a 49cc with a big bore kit, plus it'll hold up a hell of a lot better overall because everything is tuned to that motors output.



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Scootin
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PostPosted: Wed Mar 23, 2011 2:17 am    Post subject: Reply with quote

Not a bad price for a whole engine



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bigbore15379



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PostPosted: Wed Mar 23, 2011 4:52 am    Post subject: Reply with quote

Well yeah that isnt a bad price for the whole deal, but its more than I wanna put into a moped thats only worth 600 on a good day ya know..


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pall111



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PostPosted: Wed Mar 23, 2011 7:59 pm    Post subject: Reply with quote

Go for it! However you really should invest in a larger carb and gear kit... then you're going to have to tune the transmission to match... If you want to go all the way then maybe a after market cam designed to keep the valves open that little bit longer and a bigger exhaust too, after all you're doubling the displacement.

It's going to cost you quiet abit and you're bikes not going to be all that reliable, but it'll definitely be a fun experience!



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shanemsink



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PostPosted: Fri Apr 01, 2011 2:33 am    Post subject: Reply with quote

It is a good kit and its from a good seller. I bought one. Buy a 95 jet, and a high flow air filter. Get a hotter coil for the increased compression. Pick up an iridium plug too. That kit comes with heavy rollers, I think they are 8 or 9 grams. Just use your stock rollers or some 5-6 gram ones. Use the stock ones till its broken in.



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