Weed eater mountian bike

Ranger · #1 08-07-2008, 10:02 AM

I have a ryobi 31cc 2 stroke weed eater engine (I actually have 2) and want to put one on my 21 speed mountian bike. I would like the have a idler pulley chain drive but am probably going to go with a friction drive.

I just have a few questions about friction drive.

I'm planning to use a bike peg for the roller, does it need to be covered in rubber?

Could I bump start the engine ? (push bike until starts) It has quite a bit of compression.

Where do I get small pulleys and sprockets? the ryobi has about a 3/8" shaft, where could I get a pulley. Autozone, O'reilly?

Here is an interesting idea that I thought of.
Have a geared bike, use the existing 21 speed gears to get more speed (if I us a chain drive) Just take of the pedals and add a sprocket to the engine.

The bike has suspension so I doubt that I can fit the engine in the frame to make it look "cool".

I hope that most of you can answer my question about the pulleys and sprockets. Thats the one I need.

deacon · #2 08-07-2008, 10:16 AM

I can't help you with the sprocket stuff.

They make an axle peg that is textured you don't need a cover see the weed whacker tips it is has tips about friction drive with the ryobi engine.

Ranger · #3 08-07-2008, 10:32 AM

Where is the weed whacker tips? Who is they?

deacon · #4 08-07-2008, 10:38 AM

its a thread just under this one

deacon · #5 08-07-2008, 10:43 AM

You might also try the all things mtb thread just below that. I did a mountain bike 31cc conversion it is still in progress actually. If you read my mistakes you might be able to avoid the same ones.

**Ilikeabikea** · #6 08-07-2008, 03:15 PM

Check this one out http://motorbicycling.com/f14/hi-all-2687.html I bet he can tell you exactly how much reduction you will need. Bicycle tires are much larger diameter than scooter tires so you need considerably more reduction......................

Ranger · #7 08-11-2008, 04:14 PM

I'm still going with a friction drive.

Deacon: How did you attach a drive roller to your engine shaft. You keep talking about a pip nipple? How did you use a canteen as a gas tank? I siphon system?

What should I use as a gas tank? I have the one from the engine but I took it off and need a different one.

deacon · #8 08-11-2008, 06:32 PM

today I discovered that the gas tank from my bolins 31cc engine is just too small. I used it on the chain saw bike and I ran the engine out of gas and that is dangerous on a two stroke. No gas no lube you have to get them off the wheel quick so the engine stops turning.

How long is your shaft and what is the thread like. That will determine what you need to do. The last engine I mounted came from a leaf blower so it had a long shaft with a 5/16 fine thread on the shaft. If you have that shaft combo, I would go to the bike shop and buy a bmx axle peg.. but get one about an inch in diameter and textured like a file. Try to avoid the larger one that is chrome. Mine is made of alum and is 3/8 in threaded on both ends. So It fits down over the long shaft and I ran a few washers and put a 5/16 fine thread nut on it. It seems to work great.

If you have the short shaft best thing you can do is to get you a pipe nipple 3/4 inch diameter and the end cap to fit. You can drill a hole in the end cap dead center then weld a nut onto the end cap over the hold. Make sure the hole is big enough for the drive shaft to fit through.

Try to get some kind of texture on the nipple. I am trying to find something that works now. I am about to try jb weld and sand on the chainsaw bike again. It has the pipe nipple drive wheel. I am going to let it cure two or three days this time.

I was about to ask anyone if they had any suggestions for a gas tank that I could buy. I have used coke bottles, and the canteen. I am going to be looking for something I can standardize this time. You know buy five at one time.

I have discovered something interesting along the way. If you go to the auto parts store you can get some small white vacuum line connectors. Then you can use that to splice gas lines together and ever change the size of the lines. For instance I use 1/8 in lines in my tank for both lines. Using the connectors I can attach them to the different size lines for the gas and the return from the engine.

Next I plan to epoxy them to the new gas tank with the hose and filter inside so that I can just press the gas line from the engine onto them. It will allow me to change the tank on a bike without cutting out the filter each time.

The short answer is I am looking for something myself to use. The canteen holds two quarts of gas. I probably put a quart and half in it. It's important not to over fill a home made tank. Need to leave some room to pump the air into it from the return line.

Ranger · #9 08-11-2008, 07:22 PM

My shaft is 3" long with about 2 1/2" from the flywheel. It's just threaded on the tip of the shaft for the clutch. I think my best bet is to use your idea. I'll just get 2 endcaps, one for threading and the other to keep it balanced.

As for the grip I'm going to go with a flat bike tire innertube. Rubber against rubber, less wear and wont wear away the tire.

I'm still clueless about the gas tank, maybe a small propane tank? Jb a hose connection on the bottom and drill a hole where you screw on a propane accessory.

deacon · #10 08-11-2008, 07:42 PM

I'm considering this for a gas tank...
Canteen..Red (5 of them) - eBay (item 320284171163 end time Aug-14-08 12:12:43 PDT)

Sounds like my ending last time. Not sure the 2nd end cap is necessary but probably cant hurt. If you can get the nut welded onto the end cap you will be better off I think. I tried to just drill, insert the cap and tighten it down with an inside nut. that is the one that shook my engine apart. If you get heavy vibrations rethink your wheel.

I really like the long shaft with the bmx peg. but that wont work and you cant weld the ones I have they are aluminum. If you could they would be ideal in every case. If you find some steel ones on ebay about an inch od that would be the way to go. Just weld to them.