My First Attempt

[Twisted Spokes]

So, I have started my very first build of what is sure to be a new addiction. For those who did not see my Introduction, my plan is to use a 26" Mongoose mountain bike and an antique Homelite brush cutter as the platform of my build. My plan is to use a chain drive with the engine mounted above the rear wheel as there is no room inside the frame for an engine. The engine will be attached to the swing arm so chain tension will remain the same. I planned on getting much further than I did today, but some interruptions slowed me down.

I got the brush cutter running, and it does run well. I'm gonna love the noise of that 2 stroke as I am putting down the road. I tried everywhere to find the displacement and horsepower rating of the engine, but Google failed me. Hopefully it will be powerful enough for my project because there will be quite a bit of work involved and I don't want to be too disappointed.

I also removed the chain and derailleur from the mountain bike. The chain is quite rusty and will need replacing. The derailleur was in the way for now so it had to come off.

I hi jacked my sons 20" Mongoose for some parts. I cut the "swing arm" off, which may serve as the legs for my engine mount. I fit them up and I think they will work nicely. I will probably put the BMX style bars on the motorized bicycle as I like the higher stance they provide.

Unfortunately, my engine turns clockwise, so I am going to have to mount it backwards and run a jack shaft to change the direction of rotation. Not a huge deal, but another hurdle.

Some questions I have...Should I run a 41 chain for the engine? What is the best way to mount a sprocket to the right side of the rear wheel? What sprocket size engine and wheel might work best for me to get the most bang for my buck?

I will post some more pics as I progress, but so far things are sketchy.

 

[mat_man]

Hi Twisted Spokes

"The Homelite XLBC has the same power head as the XL-12 or Super XL. This is
a great unit for large brush cutting."

http://www.forestryforum.com/board/index.php?topic=11365.0;wap

Homelite XL-12 54.2cc

http://www.acresinternet.com/cscc.n...6af40002b8f7/a17d735d551f0f1e88256b78005f6a7b

I think it would be a great motor for a friction drive, if you are going to keep the pedals.

I would gear for a top speed at about 7000 to 8000 rpm.

How much do you weigh?

If you need to go chain, you will like this:

Vintage Chainsaw Bicycle
http://www.youtube.com/user/ChainsawBicycle/videos

Homemade Motorcycle
http://www.youtube.com/watch?v=TVdFyIqyIK0

Not my motorized bicycle

 

[Twisted Spokes]

Thanks Mat_Man. I really would prefer to go chain drive, but I know little about the gearing involved. I am pushing 200 lbs and have some hills around here. I would prefer to keep the pedals because I'm not sure yet exactly how much power one of these little engines has.

As of now, I am thinking 10 teeth on the engine and a 41 tooth on the rear, for now probably with an inexpensive sprocket/adapter for the right side. I am wondering how well the cheap (because this is my first attempt) spoke clamping sprockets work. If things work out the way I hope they will, this would be one of the first things I upgrade. I will also need a jack shaft to reverse the rotation from the engine, but I think any size sprocket will be OK for these as long as they match.

Thanks for the links to the vids, I gotta say I love the sound of these 2 strokes on a bicycle. Please feel free to correct any of my thoughts as I would like to avoid as many mistakes as I can along the way. I will be the first to admit that this is a new venture for me and I have a ton of things to learn, but I am finding a lot of great information here.

 

[mat_man]

This should help with jackshaft gearing calculation:

Rawge's Mini Chopper Information Site
http://rawge.bravepages.com/minichoppers/jack.htm

I would gear for something like 35 mph at 7000 rpm.

It would help to get reduction to use the largest rag joint sprocket (56T ?) with the 20" wheel.
But it would be a very good chance it would not work with a 48 spoke wheel because of
interference between the spokes and bolts.

 

[maniac57]

You can get great service from a cheap rag joint sprocket adapter as long as you install it properly. I use them on all my builds and have no issues at all with broken spokes or loosening. Just be sure it runs true and centered on your hub by shimming the center hole if needed and taking your time. Sprockets are cheap too.
Can't beat it for under $15 bucks.

 

[Twisted Spokes]

I cant wait now, I just ordered my sprockets and chain and parts for the jack shaft. Hoping to get in some good build time this coming weekend. I am starting out with 41T rear sprocket and 10T drive sprocket. My jack shaft will have 15T sprockets on both ends for now, after I get it going and see what power I have, I will use the Jack shaft to change gearing as I see fit.