power only (no pedals) setup...?

Probably the wrong forum, but has anyone ever mounted an engine on a mountain bike, so that the sproket on the engine drives one of the 2 front sprokets on the bike that are normally used for high and low range selection?

My thought was to remove the pedals, hook it up in this fashion and add a set of foot pegs to the bike to rest my feet on, this would allow the rear gear selector to still be utilized increasing the range of speeds, and decrease the engine power needed (being that I"m 6'3 and 275lbs, this is somewhat important, and where I live there's alot of hills)

If this can be done, I am very intrested in how it was set up. I have a machinist available if I would have to make parts that's not a problem.

 

[jl ws-6]

That's pretty much what CT's law is. I was originally gonna cut/chop a 3hp leaf blower motor in a bike, but the CC's and HP were over the limit, which got me to this.

I probably could get away with the 3 hp motor if I kept the speeds down, but the noise was my concern. Alot bigger muffler then standard would definately be needed.

 

[duivendyk]

Yes,it would be.I have read about sprockets as small as 8/9t they are hard on chains,20" wheels will help too.With larger displacement engine you'd be in better shape all around.The 49 cc DAX Titan (Honda clone) comes to mind,it has a 5:1 power takeoff & centrifugal clutch, you could get rid of the jack shaft then.Users seem quite pleased with it.It would have to be mounted on the left.Do you have to contend with hills?,that favors higher reduction.If you can get rid of the intermediate chain wheel(if you have one) the chain leads an much easier life.My calculations pertained of course to my Raleigh example,if as seems likely yours is different, you could easily rework the numbers.It's not a lost cause,you could not pedal the thing though, at 5k rpm the cranks are doing 200 ! rpm

 

[jl ws-6]

I'm not overly concerned with not being able to pedal, because honestly they're not even gonna be there.

I haven't bought a bike yet, so if one is better then another for the project please by all means tell me, I'm trying to keep the cost under 1200 for the whole thing including the bike, which I think is more then reasonable.

The 4 stroke does seem like a good choice because of available power, a 2 stroke would work too if I could get a decent expansion pipe for it to help it out too though. I don't know what size engines are really out there, I read alot about some claiming to be bigger then they really are, etc.etc.

My thoughts are a 50 to 70 cc would be more then adequate, and with the use of the rear sprokets providing I go with a jackshaft type setup I think the speed capabilities won't be an issue.

It's just a matter of getting the reduction needed so it has the low speed from a stop accelleration

 

[relaxxx]

I was actually thinking about doing this to a 80CC HT kit. I was going to remove the pedals, grinding off the right one to leave the normal sprockets. and on the left side adding another sprocket where the pedal arm was. Then the small chain sprocket on the left of the engine goes to the new left gear where the pedal arm was. The HT engine would need to go a bit more forward with custom mounts and the back end of the motor lowered about 20 Degrees. Sawing off the angle on the carb manifold would make it level again, thats about the angle I was looking at. I've already made sure this all fit when I was thinking about it about a month ago. It would only cost me about $180 for kit + $100 for bike and maybe $40 for extra parts

 

[jl ws-6]

Sounds like a plan. I think the jackshaft might get a little more reduction, but if you can get what's needed this way then I'd do it. The other thought, is that if you could get a really big sproket on the left side and run a small enough motor sproket you may be able to utilize all 3 sprokets on the right and the rear 7 for different speed gearing.

If the reduction is enough to get the bike moving good from a stop with the smallest front and largest rear sproket in use, you'd have 20 more gears to go for top speed.

I wonder if you could find a big sproket, like an 80 or so to put on the left side for reduction purposes. An 80 on the crank and a 10 on the motor would probably be a really good start


Does anyone sell a bike with the motor already on it ready to go (I'll assemble it that's not a problem) I just don't have time to be hunting down parts, conversion stuff, etc. If I could just buy one that's reliable in one shot, I'd do it today.

 

[Devdev21]

I have a 80 cc motorbike kit that I put together I immobilized the pedals and put them foward as foot pegs and I got the motor to idle I was wondering if there’s any other way to get the engine to start other then buying a pull start and having someone give me a push first to get the engine running I have picture of how I got it looking

 

[Chainlube]

You don't ask for much, I'd say mobilize the pedals.

 

[Frogslayer]

If you're not using the pedals a pull start should fit fine anyway. You could make some kind of custom cover to turn the engine with a drill or something but pull start sounds like your easiest way besides roll start