Starting my first MB build

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Chainreaction

Chainreaction

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Someone gave me a free HF fluxcore mig and I had always wanted a crank forward cruiser so I chopped up a mountain bike. I had never used a mig welder before so you don't want to look too close at the welding. I had to rake the front wheel out a couple inches since this picture to not catch toes.

Then I got to thinking about a gas bike. I found a 31cc Troy Bilt for $5, it will take some work to make it work, for one I have to shorten the crankshaft and get the clutch next to flywheel. Going to be a jackshaft bike.

I love riding crank forwards. I got to fire up my old computer to get all my pictures.
cfbike.jpg
 
Ludwig II

Ludwig II

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You've got room if you want to put the engine right out of the way, like the Danes did years ago.

 
Chainreaction

Chainreaction

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If it wasn't so blasted hot here in the summer I would mount it there. Imagine though sitting at a light all that warm air wafting up. I think that since the motor I am using is so small I will mount it up towards the top and middle of the triangle area.
 
Ludwig II

Ludwig II

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Short chain and or belt runs are your friend. Apart from that, you have all the room in the world to fit it.
 
Chainreaction

Chainreaction

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True. One thing I am going to try is using 25 chain/sprockets from the weedeater motor to jackshaft. I am thinking with the high rpms and maybe 2 hp torque won't be a problem on the chain. Of course 35 from jackshaft to crank.
 
Chainreaction

Chainreaction

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I made the frame without the thought of motorizing it. I am more of a function over form type so don't expect anything pretty.

I'm making the jackshaft/motormount bracket right now, only have an hour or two a day so it's slow, I'm slow as dirt designing things as it is any way. I want to avoid tensioners if possible, and any weak point design flaws that might drive me insane. Pictures in the next week or so.

It will be interesting to see how this 31cc weed eater motor does with a pipe and bigger carb. It has reed valve intake into the crankcase so maybe a bigger reed valve too. Hopefully I don't have to do a bunch of port work for those things to make a difference.
 
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Trey

Trey

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Jan 17, 2013
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Where cattle outnumber people 3 to 1.
Chainreaction- I skip the tensioner myself. Take the time and make that chain line up, right? Keep the pics coming- nice work!

Ludwig II- Thanks for that diagram pic! That really made me think. Those crafty Danes...
 
Ludwig II

Ludwig II

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I view mounting the engine behind the tube as being a stealth concept. People will look and see a normal bicycle frame, and wonder where the noise is from. It also, like I said, shortens the chain run considerable.
 
Chainreaction

Chainreaction

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I think on my next build I will make the frame so that I can mount the engine low and by the rear tire. I haven't been able to do anything lately due to health, I am too weak to even walk, d#@*n chemo.
 
Ludwig II

Ludwig II

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I hope you have good insurance, I paid a fortune for one week in America to cover all my (minor) risks.
 
Trey

Trey

$50 Cruiser
Jan 17, 2013
1,432
5
0
Where cattle outnumber people 3 to 1.
Chemo... damn. My buddy's dealing with that now too. His wifes' got him drinking ginger tea and sucking on mint candy. He swears it helps sooth his stomach. Might be worth a try. Myself, I keep feeding him Irish dinners (Guinness Extra Stout at room temp) but he doesn't always want em. That too, might be worth a try...
 
Chainreaction

Chainreaction

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I ordered some tea someone here recommended, see it that helps at all. I have already been through 6 months of chemo, but the stuff in my lungs has been creeping back. It was a bad experience but this time is a whole nother level of bad. Have to either quit or space it out cause I think this chemo will kill me as its currently being done.

Your buddy is probably in a lot of pain and pure misery, it is really impossible to describe to someone who hasn't had it. Some is worse than others too. I hope your buddy makes it.
 
Trey

Trey

$50 Cruiser
Jan 17, 2013
1,432
5
0
Where cattle outnumber people 3 to 1.
Yup, one of those things you have to know to know, I have been told. My buddy's pretty ok overall.
Do what you feel is right brother, those choices truly are yours. Best of luck to you!
When you're up to it, get to wrenchin', that's always a good time.

{ Otero... I've gotten alot of help from that direction myself:) }
 
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Chainreaction

Chainreaction

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Dec 14, 2014
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I am feeling better and have a crazy craving for V8 juice, drank about a gallon the other day. I think I'll be on my feet within a week.

So... I think I have settled on the motor I want to work with, the 49cc pocket bike motor. You can get them on ebay for $75 and up, that is cheap. Of course they need pull starter upgraded or modified. Just going to do upgrades that won't hurt reliability. Make a pipe for it, maybe upgrade the reed valves, go through it and make sure fit and finish is up to par. Looking to build a mb that is simple and reliable. Don't know what to do about a tank yet.
 
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