The beast.

[joeranton]

Okay. I am at it again. I have a chinese 80 cc with a 33 tooth rear sprocket. I am still not happy with the acceleration and top speed. I am obsessed with making fast motor BICYCLES. I don't want a dirtbike, moped, or motorcycle. I want to build a bicycle with a motor from a small dirtbike since they have gears attatched to them. The power will still be on the left side of the bicycle so it is still possible to mount the sprocke with no problem. The bike will still have a manuel clutch. It will still be able to ride like a bicycle if the engine is not too big. I dought it will be. Anyway this project will occur in the near future. Please tell me what u think.

 

[Guest]

Be careful- bike frames are not designed to carry the power or weight of an engine. The engines that we put on these frames are only around 2 hp and very light.

 

[joeranton]

Are they really only 2 hp. It feels like a lot more. How much hp does the average 80 dirtbike have? 100? I want an engine that will fit and give me the pull I want. I know I am going to have to reinforce the frame. I am definitely going to put shocks on the front. If I die riding this thing, I will surely die happy.

 

[cheezis]

If I die riding this thing, I will surely die happy.

(No need for reasoning on the reiterance of this quote)

 

[uncle_punk13]

I understand...
Working on a 65-70 M.P.H. Whizzer engine mounted in a modified 1950 Schwinn DX frame with post war (late 1940's -early 1950's) Shockmaster spring fork. If I had a camera I'd post pic.s of the progress for ya'.
Since my first tire scrubber engine, i've been on a quest for motor/bicycle speed. Many don't get it. That's alright, I'm used to that; I have small motorcycles, but my biggest kicks come from fast motored bicycles.
We are few in numbers, but we are out there...
I'd say go for it, but use moped or worksman wheels, a heavy quality frame modified with gusset plates, and definately use a heavy duty fork. Whizzer has a beauty of a hydraulic ubit, but you could possibly score a toasted moped to use for parts...
Keep us (or at least me) posted on this one, I'm interested in your project's progress!

 

[Guest]

I'm not saying don't go for it...we are all hot rodders at heart here (I think). Just take care in doing so.

To answer your q Joe, the average 100cc dirtbike engine is closer to 8-12 hp.

 

[joeranton]

That type of Hp with built in gears instead of single speed! I'm gonna be extra careful when putting this together. I only hope the rear sprocket can handle that kind of torque without messing up the rear spokes. I'm gonna be careful at first. I just need to find a way to mount the engine onto the frame. I am not really worried about whether the engine will fit or not because I know that I probably am going to have to modify the tube that goes from the front of the frame to the sprocket housing regardless. Doing this will probably make it much easier to mount the engine. This will be easier to figure out once I have the motor and bike frame in front of me.

 

[uncle_punk13]

this fella (Kenny Roberts) used a mountain bike fork with straight legs to modify his frame for his 'double-whiz' project. So this is something you might consider as far as stretching your frame and setting up for the engine/ gearbox unit motor...

Notice how he uses this for mounting. My chopper (which has the honda 90 based 'snout foward' type engine) frame also has two down tubes kinda like this, for engine mounting. So a good bending, and welding job would allow you to stretch the frame, create space for mounting, and strengthen the frame for this type of application...
Also, if you use moped wheels, the chain sprocket is bolted to the hub, and will be strong enough to handle the added power. You'll have to modify the rear dropouts of the bike frame, and possubly widen it (unless you use worksman wheels laced to a rear moped hub, then you coud modify the drop outs and just heat and lightly bent out the rear stays to accept the wier hub, but the rim would be standard size.
I'm just thinking out loud along with ya' here, as I find it to be extremely fun, hope i'm not being too overbearing here...

 

[JosephGarcia]

The 80cc doesn't have enough power for you? I have a 44 tooth sprocket and it pulls me over any hill without trouble, and goes about 45 MPH top speed. Acceleration is awesome, I pull away from all the cars at green lights, and keep up with them on straightaways.

Maybe you broke in the engine wrong?

 

[joeranton]

Engine seems to be running finel. I never heard of a stock 80cc with a 44 tooth sprocket being able to go 45 mph without a bigger drive sprocket. It shouldn't have the rpms to be able to do this.