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Post by 90GTVert on Feb 4, 2011 10:30:44 GMT -5
You can do over 30MPH on a true 49cc 139QMB stock for sure if it's not one of the bad ones. A friend bought a super cheap true 50cc and it did 37MPH (GPS, flat) stock. He's 150lbs. It won't do that with me on it @ 300lbs. That's about what I'd expect from a typical 139QMB if you get a "good one".
Keep us updated on the Metropolitanization of the GY6.
stepthrutuner makes a lot of good points.
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Post by motorhead on Feb 4, 2011 12:34:32 GMT -5
In general chinese scoots for a bad rap in general and a lot of people are pejudiced against them. Being a repair man, people always ask me what kind of scooter should I buy?
I always tell them Don't buy a chinese. But it's not because of the bike its because. An $800 Chuanl is going to be abused more than a $3,000 Vespa. At $800 it feels more like a pit bike play toy than a legitimate vehicle.
I always find $100 scooters to buy fix and resell near college campuses. And without exception they are beat to hell, odometers disengaged to hide the true mileage and scratched up. So, in general buy a new chino scoot or buy it from an old lady.
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Post by 90GTVert on Feb 4, 2011 14:55:45 GMT -5
I usually tell folks something similar to what step said. If you are willing to work, a Chinese scoot can be a good deal. If you don't wanna touch it, spend the money on a Taiwanese or Japanese scoot that has a good warranty and a dealer nearby. Chinese scoots can be good if they have a good dealer, but that's hard to come by. So many Chinese scoots are sold by folks that have no idea what they are doing and some that really don't care at all about scoots as long as they make them a few dollars. How many used car lots and random stores have you seen with scoots out front? Go talk to them about scoots and I'd bet 75% of the time you'll find out they know little more than a sales pitch and the service department is often non-existent. I had a guy tell me his dealer could not get a belt for his scooter. Must be something rare right? Nope, a 669-18-30... the most common belt for GY6 50s. lol
For most of us here though, warranties are of no concern... we're planning on voiding them anyway. :devil:
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Post by motorhead on Feb 4, 2011 15:06:53 GMT -5
I've hunted down the specs of both engines and put them side by side. I couldn't find metropolitan II specs so I used Met I specs shared with the Ruckus. The qmb specs were all over the place so I averaged all my findings. Attachments:
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Post by Fox on Feb 4, 2011 16:09:32 GMT -5
Ahah! Honda has longer stroke and higher compression it would seem so it gets more HP and torque. That splains it Lucy!  The CVT's and carbs are properly tuned for the Honda engine to maximize performance too I betcha whereas the Chinese carbs and CVT's aren't all the same. I've seen 139's with #76, #78,#90, #95 jets in them out of the crate and the roller weight varies too. I bet the Honda's are always the same. |
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Post by 90GTVert on Feb 4, 2011 16:52:06 GMT -5
Nice chart. 12:1 compression, and truly 12:1, does a lot. The liquid cooling of the Honda helps to make it more practical to use higher compression ratios.
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Post by motorhead on Feb 4, 2011 17:36:42 GMT -5
Yeah, Honda hands down makes a better engine alright. They truly bring out the potential from a 50cc. The 139QMB has so much potential just going out the muffler. If all QMBs were tuned like Metropolitans when they first came off the boats years ago, then there might not be any 2 stroke scooters on the road today. The only reason 2t 50cc hung around is because you get 10 more mph out the box vs 4T. Since Honda doesn't sell performance parts, could you imagine boring out a metropolitan to 80cc :drool: . Well, I may have found an equalizer to start redeeming QMB scoots. I have actually found a stroker crank! See the link below. Pedstop doesn't give any figures, but in the first step of metropolitanization I think this costly stroker crank could make a great foundation to start on. Then re-time the flywheel and add a racing cam (which might do something now), you'd probably bridge the gap to the CHF50. www.adrenalin-pedstop.co.uk/p/CPH_crankshaft_for_Chinese_4T__139_QMB_engine_with_NTN_bearings-2099.aspx |
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Post by 90GTVert on Feb 4, 2011 18:02:51 GMT -5
Nice find on the crank, but I don't believe it's a stroker. I think what it is is a higher quality crankshaft. That could be quite a blessing for the bigger 139QMB builds. Almost makes me wanna build my 4T up again.
As fas as eliminating 2Ts from the scooter market... Well, it's happening, but not at the hands of the GY6's performance. Emissions concerns and all that jazz are playing a big role. The GY6 50s do play a part, but it's not their performance, it's their cost. Some places are selling brand new 139QMBs for $500. Then you figure in that gas mileage is better than the typical Chinese 2T, and it's a clear choice if you're on a tight budget.
Where performance is concerned, I'm sorry, but dream on. lol The 50cc 2Ts are superior. I put some serious work into getting an honest 50MPH out of my 80cc 139QMB with my 300lbs on flat land tucked. I do feel it would be easier with a long case GY6 so a larger tire could be fitted to alter the gear ratio farther in favor of MPH though. Now, with any of my 50cc 2Ts, I basically bolted a 70cc kit on, tuned the carb, and went 50 or better.
Just for one example of what a 1E40QMB is capable of with engine work, Polini makes a 94cc setup (requires case work and plenty of cash) that will transform the little 2T into a 30+ horsepower monster scoot. That's more than you're gonna find the GY6 50's big brother putting out. Even a 250cc Kawi Ninja only puts out about 35HP IIRC. My cheap build of a 103cc stroker for one of my Tritons just pulled out of the driveway, running out of tune, and went 57MPH on flat ground, sitting up. Still needs work. The GY6 50 won't do that stuff.
Please don't take this as discouragement. I love to see people trying to push the limits of what their scooter can do. Please, by all means, make this thing something special. I love the idea!
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Post by lshigham on Feb 4, 2011 18:05:15 GMT -5
Motorhead, what makes you think it's a stroker? It's just a full circle crank.
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Post by motorhead on Feb 4, 2011 18:30:48 GMT -5
Well, it does say in the listing "CPH high mass crankshafts provide more compression." I've contacted pedstop to get more details and We'll see. It may turn out to be just a full circle crank, but I'm hoping that it isn't.
Polini makes parts for what is popular in it's localle. If Europe imported the 139QMB like we did here maybe they would have massive horsepower kits for it. Maybe not 30 hp since 2t produces theoretically 2x the power. But it's only in the last 5 years that I've seen performance QMB parts really come on the scene. If polini was here we may have 15hp qmb kits. Once 2T is regulated out (except for maybe ditechs) I bet new QMB performance parts will hit the market. Hell, untill a few hours ago none of us knew knew anyone made a full circle QMB crank. To further drive the point There are now Liquid Cooled GY6 cylinders.
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Post by erictheviking666 on Feb 4, 2011 18:45:06 GMT -5
I've hunted down the specs of both engines and put them side by side. I couldn't find metropolitan II specs so I used Met I specs shared with the Ruckus. The qmb specs were all over the place so I averaged all my findings. You know it may be possible that the QMB's are purposely kept at the specs they are at. If your 50cc Scooter was rated at 40mph and 4HP then it wouldn't qualify as a "moped" and a motorcycle endorsement would be needed to ride it. So they may have purposely kept it at the specs listed, so they can keep the "moped" status and because it's cheaper than doing a redesign. Also I can hit 45mph (GPS verified) all day long with only a 72cc BBK and would hit 37mph out of the box, I guess mine has the better tolerances. |
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Post by stepthrutuner on Feb 4, 2011 19:01:08 GMT -5
The difference in torque figures is hard to believe. The Honda puts out 51% more torque than the GY6. Regardless of the stroke and c.r. differences that much difference is hard to believe. Perhaps you should have tossed the lowest figures for the GY6 in doing the averages. You just can't trust Chinese numbers.
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Post by 90GTVert on Feb 4, 2011 19:17:47 GMT -5
You know it may be possible that the QMB's are purposely kept at the specs they are at. If your 50cc Scooter was rated at 40mph and 4HP then it wouldn't qualify as a "moped" and a motorcycle endorsement would be needed to ride it. So they may have purposely kept it at the specs listed, so they can keep the "moped" status and because it's cheaper than doing a redesign. That's a good point. Honda doesn't necessarily have to deal with legal restrictions with the Met, or at least didn't. Not sure how they do it now. I believe the purpose of those Met IIs I mentioned were to keep power and speed down so it would be the perfectly legal version of a normal Met. I think it was the same setup, but with restrictors of some sort. |
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Post by stepthrutuner on Feb 4, 2011 19:40:51 GMT -5
Here is another interesting caveat to 50cc 4t performance parameters. Below find specs (sans c.r.) for the air cooled 4v. Piaggio 4t in the Vespa S50. Specs obtained from totalmotorcycle.com webpage: www.totalmotorcycle.com/photos/2010models/2010-Vespa-S504V.htm2010 Vespa S50 4V - Specifications MSRP: $3,199 USD ENGINE TYPE Single cylinder, Hi-per 4 - 4 Stroke 4 Valve (SOHC) CYLINDER CAPACITY 49.4cc BORE x STROKE 39 mm x 41.8 mm MAX POWER AT SHAFT 3.2 kw at 8,250 rpm equivalent to 4.29hpMAX TORQUE 3.5 Nm at 6,500 rpm equivalent to 2.58 ft. lb.
MAX SPEED 39 mph (63 km/h) FUEL / TANK CAPACITY Unleaded 2.3 gallons (8.6 litres) |
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Post by motorhead on Feb 4, 2011 19:50:56 GMT -5
You know it may be possible that the QMB's are purposely kept at the specs they are at. If your 50cc Scooter was rated at 40mph and 4HP then it wouldn't qualify as a "moped" and a motorcycle endorsement would be needed to ride it. So they may have purposely kept it at the specs listed, so they can keep the "moped" status and because it's cheaper than doing a redesign. Also I can hit 45mph (GPS verified) all day long with only a 72cc BBK and would hit 37mph out of the box, I guess mine has the better tolerances. The HP and Torque figures for the QMB engine in my chart differ by +-.3. Not much. I found an seller on ebay who had the Hp rating at 2.2 hp and tossed it out. So I actually averaged the high numbers. I don't believe that the Chinese QMB power is kept down. Because Chinese minarellis still make 4.5hp and come in our market with moped certification. Correct me if I am wrong but Honda/China developed the GY6 together. After they split then the Chinese miniaturized the GY6 and created the QMB all on their own. Where as China produced minarellis to contractor specs for Japan and Europe so they retained the knowledge. I think that's why most QMB s fall short of your bike. You should consider yourself a very lucky man. The factory workers must have stayed at a holiday inn the night before building your bike. |
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