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Post by eli0shin on May 11, 2015 22:28:54 GMT -5
about 2 weeks ago i bought a chinese 49.5cc 139qmb md50qt-5 scooter it is incredibly fast compared to what others have told me about these scooters. It was bought second-hand so i am unsure what has been done to it it already but besides 1000miles on the odometer it looks to be as shipped. i have easily topped out the speedometer at 50mph+ however getting it moving from a stop sign or light can be slow sometimes requiring a push with my foot so i dont get rear-ended. it seems to fight momentarily after the clutch engages at 2200rpm before it quicky takes off, almost like it can barely move it from a stop. another question i have had is i see many people reporting revving to 7/8000rpm any the specs online say the max hp number is at 7500rpm. The only time i have seen the needle at 7000 was at 50+mph downhill i only weigh 135 so that cant be why and i have never heard a rev limiter kick in so i would like to assume that isnt the issue. Where should the powerband on such a scooter be? mine is strictly between 5-6000rpm. Im kinda groping around in the dark right now any help would be apreciated.   |
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Post by niz76 on May 11, 2015 22:35:49 GMT -5
WELCOME!! Seems like you got a fast QMB there! Luckily it seems that what might help you out is also one of the cheapest mods! Clutch springs! They let the RPM's rise higher before the scoot starts moving so you don't have to use your feet haha. Sounds like you may benefit from lighter roller weights also...   |
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Post by humanshield on May 11, 2015 23:09:20 GMT -5
Just remember most Chinese speedometers aren't very accurate. I sometimes see bone stock 49cc scooters indicating over 60 mph (not kph).
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Post by eli0shin on May 11, 2015 23:39:42 GMT -5
thanks a lot i will definitely give those a try as far as the power band where should that usually sit on these scooters and why cant i get it past 6000rpm?
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Post by Elektrey on May 11, 2015 23:55:24 GMT -5
1. most speedos are off by 5-10mph
2. ignore the "spec sheet" as its pretty useless for peak power stats
3. get clutch springs to delay clutch engagement
4. tune your cvt so you are in the powerband.
5. powerband on a 4 stroke gy6 i'm not sure and it'd be better to just "feel it out" yourself if you can. If I went off of what I read online about my setup I would think my powerband is between 9 and 10k closer to 10k but in reality I'm at 8.5k-ish. Point is every setup is different there is no cookie cutter.
6. you may be limited by the CDI to 6k rpm.
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Post by eli0shin on May 12, 2015 0:48:09 GMT -5
i just had an idea my scooter has 12" rims on it (from the factory) maybe the larger final drive gear(the wheel) is responsible for all this
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Post by TurboTyler on May 12, 2015 1:06:20 GMT -5
You need to take the weights out and weigh them then let us know what you have. It sounds like you may have 9 gram roller weights in it. I suggest 6 gram roller weights on a bbk 49cc
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Post by Elektrey on May 12, 2015 10:29:43 GMT -5
i just had an idea my scooter has 12" rims on it (from the factory) maybe the larger final drive gear(the wheel) is responsible for all this 12" vs 10" rims will result in a larger final gear which will give you a higher bottom and top gear. makes sense to me. |
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Post by Fox on May 12, 2015 11:33:18 GMT -5
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Post by eli0shin on May 13, 2015 21:47:36 GMT -5
it looks like the problem was a missing exhaust manifold nut (1of2) its still not quick off the line but it doesnt hesitate like it used to i also noticed that it now revs to 7000 rpm
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