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trouble with motorbike Answered

so I have purchased a 25cc 2 cycle homelite brand trimlite weedeater, and have decided to put it on a bike.  my drive system of choice is friction drive. i have a 1 in diamater alluminum knurled roller that is held on by set screws. my question is, it doesent work. i have no cintrifigul clutch, so i must first pedal to start the bike. then i throttle on the motor and stop peadaling. the motor turns on, but quickly bogs down and dies, and i don't know why. am i doing something wrong? please help. this is very close to the system that i have. https://www.instructables.com/id/How-to-Strap-a-Leaf-Blower-Engine-to-a-Bike-and-Go/



3 years ago

it may be the screen in the carb. Take the plate off the side and check the screen. Clean all other holes with small wire ( bread tie). I have 25 tb grass trimmer had the that problem.

What size is your bike tire? Im in the process of building a chainsaw powerd bike. And your gear ratio is Very important. These small engines are designed to run anywhere between 10,000 and 12,000 RPM, Some as high as 14k ! This is where the most power is being made, and to use it right you need to be geared LOW. I have a 12/1 laying around im thinking about using and I think this is even way to high. You can also richen up the high end circuit of the carb to get more tq, but you lose some rpm. Good luck.

The weedeater wants to spin at a high RPM in order to keep running. The bike is starting from a stop will be sitting at zero rpm. So the weedeater stops. If you try running the weedeater while the bike is in motion and it still stops, then it is because the gear ratio is still off by too much. Think of how hard it would be to PEDAL a bike if you started off in FIFTEENTH gear from a stop. So now you add some gear reduction so the weed eater turns 100 turns but the bicycle wheel only turns ONE turn. That might work... but you are still going to have problems starting the bicycle from a dead stop. That is where you need the clutch. That is just a disk that SLIPS untill the bike is up to full speed, then it stops slipping. One man i read about solved all of these problems of construction by building a bicycle powered by a small motor connected to a large model airplane propeller. No gearing and no clutch needed. Since he lived in an area with NO HILLS.. he could drive around on the bike pretty fast. I saw the story in a book. The guy lives in southern missouri, USA.

yes, i understand that gearing could be the problem, accept that im using a friction drive system, one that doesn't use gears. I'm also using a 1in roller and a 25cc engine, a gearing combonation that i have seen numerous places so that i know it is feasible. although i do like the propeller idea, that seems kinda cool. but i think my problem lies somewhere else, like the motor or mount or something.

No clutch, no gearing either.
Have you considered a chain-drive?
You want high revs, but you're not getting enough speed: bigger diameter drive wheel or gearing.


ive tried 2 different drive wheels: a 2in steel roller and a 1 in allluminum roller, both with the same result: it starts out at almost full rpm when i kick in the motor, then bogs down and dies. also i have tried chain drive before with no succeess. i currently have an electric friction drive bike that works just fine so i know that my mount is good, i just cant figure out why it dies.