This engine ruined my bike

Grongebis · May 20, 2012

I got my bike all built and adjusted and running great, and then about a mile into my trip, my chain tensioner decided that it would throw itself into my spokes, ripping about five or six of them completely out of the wheel, ruining the chain, motor mounts, wheel assembly, and tensioner. even the tire itself is wore down from having to push it home locked up.

On top of it all, I have a rediculous burn on the side of my knee from the engine.

Toadmund · May 20, 2012

That's crappy!
I could foresee that happening to me.
I made a brace for it.
Some guys even screw a self tapping screw into the chainstay to stop it from rotating.

I just could not afford something like that.

DIANY · May 20, 2012

yeah..the tensioner is a NO,NO, i think the spring loaded ones might be ok tho....

young grease monkey · May 20, 2012

That really sucks, I hope you don't get discouraged from continuing to build and ride motorized bikes. I don't use the chain tensioners, instead I put spacers in between the rear engine mount block and the engine so the engine is moved forward and the chain is tighter. Is the rim damaged? Spokes are cheap, just need to install them. The spokes may have pulled on the rim and damaged the holes. If that's the case you need a new rim. I hope it wasn't a really expensive bike.

GearNut · May 20, 2012

Those kit tensioners have ruined many, many good rear wheels and caused waaay too many cuts and scrapes on riders.
Sorry to hear that it messed up the motor mounts too.

http://motorbicycling.com/showthread.php?t=11815
In the above thread by BarelyAWake, it shows virtually the same tensioner I made for my Atlas build in the second photo down. I actually copied my tensioner idea from this picture. There is no way it can ever get thrown into the spokes.

Here are more threads relating to tensioner ideas. There are many more threads but I will stop here, you get the idea.
http://motorbicycling.com/showthread.php?t=2063
http://motorbicycling.com/showthread.php?t=890

Good luck with your repairs and I hope that you don't give up due to a poorly designed factory failure of a part.

taffyapple · May 21, 2012

i overcome this problem before it happened to me as i thought about what would happen,i used inner tube first on the frame ( 2 layers) and bolted the tensioner over it,it never failed

dragray · May 21, 2012

this is exactly why i always tell people to install the engines on these bikes correctly.
Take your time, read the posts to see what works and what doesn't.
9 times out of 10, a guy will just bolt an engine kit to a bike as quickly as possible, and incorrectly.
then when it fails, it's the engines fault, and all china engines are deemed as junk.
i'm telling you, time and patience, along with mechanical knowledge and fabrication skills is what's needed to build one of these bikes to make it work right and to last a long time.
without all 4 of those skills, the subject of the original post here is the result...9 times out of 10 ALWAYS!

Al.Fisherman · May 21, 2012

Engine didn't ruin your bike, the improper instillation did. Can't really be all your fault, the lack of proper instructions has some to blame.

rohmell · May 22, 2012

I feel that the chain tensioners come with too much 'curve' in the mounting area, then when fully tightened, they don't grip tight enough for a secure hold. I always put the tensioner in a vise and flatten out the 'curve', and use longer mounting bolts.
Never, even a failure, nor any movement of the tensioner after this procedure has been done.

Hoze513 · May 22, 2012

I put two pieces of rubber in between the frame and chain tension. And my chain tension has not move once. But Iam soon going to put a spring tension.

dragray · May 22, 2012

the stock kit chain tensioner is garbage, no matter what you do to it.
It's a horrible design, and even if you do get it to stay in place, it won't last.
there's no bearing in the roller, and the roller is cheap, hard plaztic. on top of that (in my opinion) it looks like a peice of junk that was whipped up in someones backyard, with left over barbeque grill parts.
You can make a far better chain tensioner out of a derailer, with a little inginuity and fabricating.

wayne z · May 22, 2012

I built 6 of these kits in the last 2 years. They all had a sealed bearing in the roller.
I simply bolted a piece of 1"x1" aluminum angle about 10" long to the idler bracket at the top, with the aluminum angle's ends bearing against the outside of the chain and seat stays. Use zipties on the ends to keep it from moving around.

Very easy and very reliable.

DaveC · May 22, 2012

I wrapped electricans tape around the frame to give the tensioner something to grip. I also had to twist the mount in a vice with a pipe wrench to align the tensioner with the chain or it wanted to derail the chain off the sprocket when I rolled the bike backwards.

The bike had an aluminum frame so it didn't seem to me to be a good idea to drill a hole for a screw

Acraze · May 22, 2012

so can we all agree that it was crap chain tensioner and Not the engine. makes me rethink my setup.

Grongebis · May 23, 2012

rohmell said:
I feel that the chain tensioners come with too much 'curve' in the mounting area, then when fully tightened, they don't grip tight enough for a secure hold. I always put the tensioner in a vise and flatten out the 'curve', and use longer mounting bolts.
Never, even a failure, nor any movement of the tensioner after this procedure has been done.

this is exactly what I did, too!!

another thing i did was have a radiator hose clamp running from the tensioner to the back part of the frame. it aparently did not help..

I want one of those ones that mounts from the top and bottom. or spring loaded.

maurtis · May 23, 2012

Grongebis said:
I want one of those ones that mounts from the top and bottom. or spring loaded.

Agreed, I am running a stock 4 bolt tensioner and have been meaning to make one of those simple top/bottom bar mounts. Looks like this might be my project for the weekend!

dragray · May 23, 2012

wayne z said:
I built 6 of these kits in the last 2 years. They all had a sealed bearing in the roller.
I simply bolted a piece of 1"x1" aluminum angle about 10" long to the idler bracket at the top, with the aluminum angle's ends bearing against the outside of the chain and seat stays. Use zipties on the ends to keep it from moving around.

Very easy and very reliable.

ok, that's fine and it probably works fine.
BUT, it probably looks like a crazy contraption bolted to the bike.

dragray · May 23, 2012

on one of my bikes, I made a hidden tensioner out of a delrin block shaped like a wedge..
it acts as a slider rather than a roller tensioner.
you can see sliders on some diertbikes, which are made out of plastic. these sliders, keep the chain from rubbing on the swing arm.
on this bike of mone, the chain slides across the wedge and the wedge keeps tension on the chain.
simple, effective and it's hidden out of sight.

On my other bike, i made a spring loaded chain tensioner out of a chain derailer.
simple, easy and it works excellent, plus it's made if minimal parts so it's not like there's a bunch of parts bolted to the frame with a rolle ron it (an eye-sore).
mine is actually bolted to the engine, and if you're not looking for it, you won't see it.
I'm sorry, but i like clean lines and having a big honkin chain tensioner, with added aluminum, metal , wire tires, etc, bolted to the frame just looks goofy to me,.

waistofhumanspace · May 23, 2012

I have had my chain (guide) twist into my spokes too...This is the best looking spring loaded chain tensioner I have seen

It is my experience that the need for a spring loaded chain tensioner comes from improper sprocket alignment, Rag joint sprockets dont seem to roll true, I picked up a highspeed hub with the sprocket & band brake & I have not had a problem since.

rustycase · May 23, 2012

WoW!

That IS a really good looking tensioner, W !

I think it might work better if it were closer to the rear sprocket, though.

Otherwise... IMO, using any sort of rubber product between the stock tensioner clamping bracket and the chainstay is not the best of ideas.
I feel any tensioner should be firmly attached.

Best
rc

This engine ruined my bike

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