Weedwacker bike weight limit?

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#1
Hey guys, I’ve got quite a question. For the people here who have built a weedwacker friction bike, I was wondering what the maximum weight limit those little 28cc motors can do? I’m a pretty hefty guy at 230 pounds and want to build one, but would it push me?

Thanks,
Andrew
 


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#2
The more weight you have the more cc you need to have, but cc is all a joke they don't make a
80 cc they do make a 49cc that is 1cc below legal limit of 50cc so if you look at a 66cc from the other side say orient its 99cc that makes up for the 1cc in reference that its legal at 49cc cuz 50cc would come under law regulations.
Me I don't care about the cc it's the horse power that's going to do the work not the cc. So is working out for your weight?
 

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#3
The more weight you have the more cc you need to have, but cc is all a joke they don't make a
80 cc they do make a 49cc that is 1cc below legal limit of 50cc so if you look at a 66cc from the other side say orient its 99cc that makes up for the 1cc in reference that its legal at 49cc cuz 50cc would come under law regulations.
Me I don't care about the cc it's the horse power that's going to do the work not the cc. So is working out for your weight?
Sometimes I think Russia hired you to trollollol the Americans. While the reptilians were injecting you with that mind control syrum did you happen to see my missing bag of popsicle sticks?
 

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#4
Hey guys, I’ve got quite a question. For the people here who have built a weedwacker friction bike, I was wondering what the maximum weight limit those little 28cc motors can do? I’m a pretty hefty guy at 230 pounds and want to build one, but would it push me?

Thanks,
Andrew
I haven't built a weed whacker bike but I thought the thread needs at least one sensible reply lol.
My first motorised vehicle was a 27cc mini scooter, and with my weight which is similar to yours it was able to accelerate reasonably and climb reasonable inclines with the gearing it had, but that gearing obviously limited top speed, around 20-25mph, above that the little engine was revving its nuts off, which quickly killed it.
Having the ability to pedal along with the engine power you should be able to get a better top speed with still reasonable acceleration and climbing, as long as the friction drum has sufficient traction on the tyre.
 

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#5
I haven't built a weed whacker bike but I thought the thread needs at least one sensible reply lol.
My first motorised vehicle was a 27cc mini scooter, and with my weight which is similar to yours it was able to accelerate reasonably and climb reasonable inclines with the gearing it had, but that gearing obviously limited top speed, around 20-25mph, above that the little engine was revving its nuts off, which quickly killed it.
Having the ability to pedal along with the engine power you should be able to get a better top speed with still reasonable acceleration and climbing, as long as the friction drum has sufficient traction on the tyre.
All true i have a Bike Machine Motor sold back in the 50's it is about 35 cc, friction drive. Pulls my 230 # around with ease. about 25 mph. ....Curt
 

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#6
I haven't built a weed whacker bike but I thought the thread needs at least one sensible reply lol.
My first motorised vehicle was a 27cc mini scooter, and with my weight which is similar to yours it was able to accelerate reasonably and climb reasonable inclines with the gearing it had, but that gearing obviously limited top speed, around 20-25mph, above that the little engine was revving its nuts off, which quickly killed it.
Having the ability to pedal along with the engine power you should be able to get a better top speed with still reasonable acceleration and climbing, as long as the friction drum has sufficient traction on the tyre.
Thanks, I think I’ll give it a try! If I can engineer a way to make the friction drum swappable, then I can adjust the gear ratio perfectly. Thanks for the reply!
 







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#13
Ya all you need is a dremel and some sandpaper. Some of those engines have a divider in the middle of the port you could delete but not all have it. They make little expansion chambers for the hpi baja and rc engines you could adapt. I actually want to that to see if it actually helps the top speed or anything. I have 3 power heads and a chainsaw but they all have carb problems. I have an old 31cc ryobi that I think needs a magneto, a 25cc homelite that runs but has a bad carb and an old hedge trimmer engine that stripped the key on the flywheel. The diaphragm carbs are a pain. If they were slide carbs it would be much better. Maybe I could adapt the stock nt carbs for one of those engines, perhaps the homelite chainsaw.
 


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#15
Ya all you need is a dremel and some sandpaper. Some of those engines have a divider in the middle of the port you could delete but not all have it. They make little expansion chambers for the hpi baja and rc engines you could adapt. I actually want to that to see if it actually helps the top speed or anything. I have 3 power heads and a chainsaw but they all have carb problems. I have an old 31cc ryobi that I think needs a magneto, a 25cc homelite that runs but has a bad carb and an old hedge trimmer engine that stripped the key on the flywheel. The diaphragm carbs are a pain. If they were slide carbs it would be much better. Maybe I could adapt the stock nt carbs for one of those engines, perhaps the homelite chainsaw.
Im not too familiar with porting, we are talking about the intake port right?
 

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#16

Frankenstein

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#17
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#18
Im not too familiar with porting, we are talking about the intake port right?
No! absolutely don't attempt to 'port' a weedeater engine!

Espcially if it's a decent model like an Echo or Tanaka. You'll either really muck up the cylinder and ruin it or cause a tuning change that ruins it's power spread. Honestly I don't know where people think you can apply China Girl engine tuning techniques to precision little weedeater engines. You'll just end up ruining what was a good running engine. The best thing you can hope for is to check the spark arrester, if so equipped, and clean the mesh screen and maybe fab a small performance aircleaner to the intake, but that will take some serious tuning skill. Weedies as a rule like RPMs and should be 'geared' conservatively. 1 and 1/8" inch diameter driver friction wheel is within the ballpark for something that might clim moderate hills with leg assist. At this engine size the engines should be bicycle assistance engines, not the primary power source.

Read this thread in MotorBicycling's DIY subforum: https://motorbicycling.com/threads/minimalist-fd.62572/

Cannonball2 builds some of the most sanitary light bike drives on any Motorized bike forum and should be an inspiration for those who want to build DIY friction drives, the engine in his thread keeps it's auto clutch working so you don't have to raise the engine off the tire at stops.

 
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#19
No! absolutely don't attempt to 'port' a weedeater engine!

Espcially if it's a decent model like an Echo or Tanaka. You'll either really muck up the cylinder and ruin it or cause a tuning change that ruins it's power spread. Honestly I don't know where people think you can apply China Girl engine tuning techniques to precision little weedeater engines. You'll just end up ruining what was a good running engine. The best thing you can hope for is to check the spark arrester, if so equipped, and clean the mesh screen and maybe fab a small performance aircleaner to the intake, but that will take some serious tuning skill. Weedies as a rule like RPMs and should be 'geared' conservatively. 1 and 1/8" inch diameter driver friction wheel is within the ballpark for something that might clim moderate hills with leg assist. At this engine size the engines should be bicycle assistance engines, not the primary power source.

Read this thread in MotorBicycling's DIY subforum: https://motorbicycling.com/threads/minimalist-fd.62572/

Cannonball2 builds some of the most sanitary light bike drives on any Motorized bike forum and should be an inspiration for those who want to build DIY friction drives, the engine in his thread keeps it's auto clutch working so you don't have to raise the engine off the tire at stops.

Thanks for the reply, that is exactly what’s I was looking for! I probably won’t port the engine just because of my inexperience, but if I install a small spindle it should give decently torque and a low speed. Thanks
 

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#20
Thanks for the reply, that is exactly what’s I was looking for! I probably won’t port the engine just because of my inexperience, but if I install a small spindle it should give decently torque and a low speed. Thanks
Hi Andrew.

Please look carefully at Cannonball2's description of his weedie conversion. He's using the twin ball bearing weedeater line head driver off of an old Echo 21 cc as the carrier for the friction drive roller. If you try to run the roller from the engine itself, if there's no bearing support off the clutch it drives, it's side loading will destroy the clutch drive in short order. Especially if it's a cheap weedeater like a Ryobi Toro, Poulan or other US domestic produced weedie. It will be worth your time to keep an eye out at small engine repair shops, Craigslists, garahe sales and other venues to find an older, quality, curved shaft weedeater You use the lower assembly that drives the line cutter advance head. it has two fair sized ball bearings that can handle the side loading a friction drive will impose on the drive roller, otherwise you have to support both sides of the friction roller which increases the complexity of your installation.

Also take into account that you will need some fabrications skills and tools to cut and drill angle iron, steel sheeting, and tubing to make this work. It will not be easy for a beginner.
 


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