Transplanting motor to new bike, derailer issues

smokinbenrage

New Member
May 18, 2008
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Ok, so I have purchased a new bike from the local thrift store. It is a Huffy Havannah or Savannah (Don't have the bike here with me right now while I am typing this thread). I installed everything and when it was time to mount the engine, the derailer is in the way. I mounted the engine above the derailer and now there is a 2-3" gap between the front tube and the front engine mount. Does anyone know of an adjustable bracket I can use or do I have to fab one my self?

Thanks,

Ben
 

smokinbenrage

New Member
May 18, 2008
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Well, I have finished transplanting my engine kit onto my new bike, it looks absolutly awesome! I decided to remove the front derailer so that the engine mounts properly... thanks for the tip! I still have a few problems. First thing first. I mounted the chain tensioner on the bike and found that the bottom tube is too small, I decided to add some metal shims under the bracket to see if it would make up for the difference, it seems to work... kinda. The problem is that when I fired up the engine the chain pulled the tensioner and bracket into the wheel and seriously bent 4 of my spokes. I have a few ideas of why this may have happened:

1. Chain tensioner wheel is worn out and sliding around too much.
2. I noticed that the bottom bars are at quite a bit of an angle which caused the chain to grab the edge of the tensioner wheel and throw the tensioner assembly into the wheel.
3. The main engine sprocket and the wheel sprocket do not line up, it seems that the wheel sprocket sticks out farther than the engine sprocket.
4. Although I have added the metal shims to the mounting bracket and I can barely move the assembly with my hand, the engine has so much torque that the chain just pushes down on the tensioner wheel and flips it into the bicycle wheel.

My second question is... what do I do about my bent spokes? I would rather not bring it into the bicycle shop to get fixed because I want to learn how to do it myself.

I am at a loss on how to fix these issues, maybe someone can point me in the right direction as how to fix these.

Thanks,

Ben
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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First- the spokes, buy new ones, pull off the wheel and tire and replace them one at a time tightening them before you go onto the next.

Tensioner_ there are several fixes for that- one is to use cupped washers (do a search here) or drill a hole through it and the frame and use a small self tapping sheet metal screw to secure it. Also, you will need to take it off, put it in a vise and twist it a bit so it runs in-line with the chain.

Now, about that sprocket problem....I'd have to see what you have going on there, I haven't had a problem with things lining up. Is everything in the right place and order?
 

deacon

minor bike philosopher
Jan 15, 2008
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north carolina
I ride cruisers so I'm not sure how you tension a mountain bike rear wheel, but I adjust the wheel for the motor chain, then use the tensioner on the bike chain. Might have to take a link out of the motor chain to do that, The bike chain had a heck of a lot less torque.

Joe's spoke idea was how I did it. I used duck tape instead of a rim tape to cover the spoke ends inside the wheel but do use something there.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
63
up north now
Bottom side, or the "return side".

I originally mounted my first build to the top and it worked O.K., but worked much better on the bottom. Smoother and less wear and tear on the tensioner.
 

cityevader

New Member
May 11, 2008
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Santa Cruiz, CA
Tensioners are designed to NOT be on the drive side of the chain.

How far off is the sprocket alignment?
If you were looking from behind, and eyeballed the vertical line through the rear sprocket, and did the same with the front with the chain attached...are they way off? Mine was,both vertically and horizontally, and I manage to tilt the engine to the left enough to line them mostly up. THEN I tightened up the tensioner to be in-line with these. If it's inline the only load would be up/down, not side to side, and wouldn't pull it into spokes.