Will'smotobikes19
Well-Known Member
The 49cc 4 stroke isn't a bad motor it can carry heavier people decent, 38mph on project farm's video testing but he's not that heavy. Bigger rear sprocket will help 56 tooth or so will carry you right up.
how poorly would a stock 142F perform with a Comet knockoff TAV ?
- Thread starter freddi
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The_Aleman
Well-Known Member
Yeah, but geared for a 38MPH flatout means one won't have much hillclimbing unless one is a 2-ball Lance chevrolegging like a 3-ball.
Then there's the wind. Even tho I'm a ballhead, I'm not very aerodynamic, being about Muhammad Ali size wearing 38W36L jeans. I've seen headwinds that bring GXH50 and HS49 down to 18-20MPH with 15:1 gearing. Those engines lack torque for heavy loads with heavy dudes unless one runs ratios over 20:1, which means top speed under 30MPH with a single-speed. Some are fine with that, some want to consistently travel over 30MPH. To have both, one needs a shift-kit or a CVT. CVTs aren't power-efficient enough for the really small gas engines. They require considerable power to operate.
Shift-kit - that's a love/hate affair from my perspective. If you've ever rocketed off the line full-throttle with a 37.5:1 reduction to a 15MPH redline, you might smile, pedaling furiously doing the "MTB-pause" with each blip of the throttle at each shift, until you stop, park, and realize your tire rotated on the rim and destroyed your tube's valve stem. Again. That's happened to me quite a few times. Not to mention mucking with 3 chains and a belt in the long term. The belt was the easy part, the tension of the outer jackshaft chain is not. Putting engine power through a bicycle drivetrain can be tricky and definitely shortens maintenance intervals. Derailleur chains are designed to be replaced roughly every 500 miles with pedal power.
At least with a 79, 97, and 99 you have about twice as much average torque all the way down to 1800 RPM. If the engine is set up to make 4HP at 5000 RPM, then it'll be making about that much torque at the same RPM (crossover always 5252), which means a very broad torque curve. The 97CC flathead is the most compact of those 3 engines, it's not much larger than a HS49/HS53 (142F/144F). That's the engine I'd replace my own 142F with, if I were to re-do the drivetrain.
Then there's the wind. Even tho I'm a ballhead, I'm not very aerodynamic, being about Muhammad Ali size wearing 38W36L jeans. I've seen headwinds that bring GXH50 and HS49 down to 18-20MPH with 15:1 gearing. Those engines lack torque for heavy loads with heavy dudes unless one runs ratios over 20:1, which means top speed under 30MPH with a single-speed. Some are fine with that, some want to consistently travel over 30MPH. To have both, one needs a shift-kit or a CVT. CVTs aren't power-efficient enough for the really small gas engines. They require considerable power to operate.
Shift-kit - that's a love/hate affair from my perspective. If you've ever rocketed off the line full-throttle with a 37.5:1 reduction to a 15MPH redline, you might smile, pedaling furiously doing the "MTB-pause" with each blip of the throttle at each shift, until you stop, park, and realize your tire rotated on the rim and destroyed your tube's valve stem. Again. That's happened to me quite a few times. Not to mention mucking with 3 chains and a belt in the long term. The belt was the easy part, the tension of the outer jackshaft chain is not. Putting engine power through a bicycle drivetrain can be tricky and definitely shortens maintenance intervals. Derailleur chains are designed to be replaced roughly every 500 miles with pedal power.
At least with a 79, 97, and 99 you have about twice as much average torque all the way down to 1800 RPM. If the engine is set up to make 4HP at 5000 RPM, then it'll be making about that much torque at the same RPM (crossover always 5252), which means a very broad torque curve. The 97CC flathead is the most compact of those 3 engines, it's not much larger than a HS49/HS53 (142F/144F). That's the engine I'd replace my own 142F with, if I were to re-do the drivetrain.
regarding spokes being ripped out with rag-joint sprockets, do the CNC adapters which clamp around the hub significantly lessen
destruction? - the ones I see have three points through the spokes to attach to a sprocket. That looks pretty stressful in its own right,
on gearing I know the asymmetric belt TAV can achieve ~3:1 ratio - assuming the right motor to make it work.
I've got Walmart Schwinn "Swindler" ... spokes look very light - like 16ga or maybe even 18 -? - it'll probably get a a standard cheap 49cc 2-stoke kit rendering it usable only on fairly flat ground. That drag (?) minibike of mine with the big block motor needs some precision cutting and welding - too many broken toys.
destruction? - the ones I see have three points through the spokes to attach to a sprocket. That looks pretty stressful in its own right,
on gearing I know the asymmetric belt TAV can achieve ~3:1 ratio - assuming the right motor to make it work.
I've got Walmart Schwinn "Swindler" ... spokes look very light - like 16ga or maybe even 18 -? - it'll probably get a a standard cheap 49cc 2-stoke kit rendering it usable only on fairly flat ground. That drag (?) minibike of mine with the big block motor needs some precision cutting and welding - too many broken toys.
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JerboaJohn
Well-Known Member
Schwinn = 14ga,, like most box store bikes...
the 3 arms rest against the spokes, tho these are so much better than rag joints, but spokes do get bent as these creep into the spokes. scuff up your hub and the inner diam of the adapter.
they are the most common setup ppl are using. only way to get better is for disc brake mount with the 6 bolts to the hub. little bit involved tho if you want to keep the rear disc.
I'm looking at mine now, think it has abt 500 miles with this wheel and it has slipped 2mm into the spokes. torque the 2 bolts tight n use blue loctite you'll be ok for a long time
the 3 arms rest against the spokes, tho these are so much better than rag joints, but spokes do get bent as these creep into the spokes. scuff up your hub and the inner diam of the adapter.
they are the most common setup ppl are using. only way to get better is for disc brake mount with the 6 bolts to the hub. little bit involved tho if you want to keep the rear disc.
I'm looking at mine now, think it has abt 500 miles with this wheel and it has slipped 2mm into the spokes. torque the 2 bolts tight n use blue loctite you'll be ok for a long time
Will'smotobikes19
Well-Known Member
I've noticed it does that as well. What we need is a key or set screw to keep one or both halves in place so sudden acceleration or load doesn't make it slip.
FNTPuck
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If you sand/mill out just a fraction of a mm on the base of each side it won't creep anymore. Gotta mic your hub then mic the hole the mount makes when held together flush - some bikes have slightly larger or smaller hubs than expected. Split the difference and take that amount off each side so its still a fairly round circle. I just aim for ~.2mm smaller than hub diameter so it grabs it tight but doesn't cause a big gap between pieces or too much pressure on it. Too tight will likely crush the cheap hubs, and too loose will make it push into the spokes like above. Blue loctite on the bolts are a must as well.