**important Questions**

bowlersp

New Member
Jun 29, 2008
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So, i have been riding my motor bike to work monday and tuesday. but on the way home on yesterday the chain slipped of the pulley system and pulled the pulley lever and chain into the spokes of my back wheel and doing so broke 3 spokes, which destroyed the back wheel by bending the crap out of it.

now, the chain was a little loose, which may have caused this to happen. i fixed the problem by getting a different back wheel that i had from another bike that i had.

my question to you guys is do they make a better pulley's than the one i got with my thatsdax engine kit? maybe one that is made out of some kind of metal and that has higher sidings to prevent the chain from slipping off?

thanks for your help!!
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
The reason the chain falls off can be several reasons- One the chain is too tight, pulling the tensioner over sideways. Also, improper chain alignment will not help.

You can drill a small hole through the tensioner and chainstay and put a small sheet metal screw through it.

The Dax tensioner with the bearing in it is a pretty good one, once set up properly.
 

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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There are ways to get rid of that evil chain and tensioner altogether. How many broken engine/bike/spokes/wheel stories are out there due to the lousy stretch-o-matic chain and plastic tensioner? OK I sound like a commercial but this was my driving force for MONTHS......sorry. Check it out, lose the chain, gain the gears.
 

bowlersp

New Member
Jun 29, 2008
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The reason the chain falls off can be several reasons- One the chain is too tight, pulling the tensioner over sideways. Also, improper chain alignment will not help.

You can drill a small hole through the tensioner and chainstay and put a small sheet metal screw through it.

The Dax tensioner with the bearing in it is a pretty good one, once set up properly.

got any pictures of these suggestions? i'm not good with mechanical terms. i'm more of a picture guy. thanks for your help!!
 

jasonh

New Member
Jun 23, 2008
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The chainstay is the bar the tensioner is mounted to. Basically drill a hole through the bracket and into that bar and put a screw in there. That should keep it from rotating on the bar.

You could also try something like this:

http://motorbicycling.com/f30/motorized-bicycle-spring-loaded-chain-tensioner-1128.html

Or if you've got the money, go with Pablo's kit and you'll get rid of the tensioner, the extra sprocket, and the stretchy chain.
 

bowlersp

New Member
Jun 29, 2008
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ahhh, i see what you mean. drill a hole through the the tensioner that has the two bolts tightened around it to keep it from falling off the bike frame and then put a bolt through it to keep it from moving. would you drill the hole through it while it is installed on the bike or take the pieces off the bike?

also, i saw on the daxs webpage that they have a stronger pulley. would you recommend it or a different pulley? can i pick up just any pulley like at lowes or home depot? thanks for your help.
 

jasonh

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Jun 23, 2008
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you don't want to drill all the way through the chainstay. Just one side of the tube, and use a sheetmetal screw. I would just do it on the bike so everything lines up.

For a new one, I've heard nothing but good things about the spring-loaded TSC one I linked to.
 

Dave31

Active Member
Mar 1, 2008
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Aztlán, Arizona
I've been using the stock tensioner and roller for 5 years and over 4,000 miles?? I have had no problems what so ever. I do have a roller off a MC chain roller for one the times comes but that day has not come yet.

Pic from Norm
 

bowlersp

New Member
Jun 29, 2008
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so you drilled two holes in the tensioner, indicated by the red circles. i just would like a pulley that has bigger sides so i know for sure that the chain won't slip off. anybody know where to buy some?
 

Dave31

Active Member
Mar 1, 2008
11,204
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Aztlán, Arizona
so you drilled two holes in the tensioner, indicated by the red circles. i just would like a pulley that has bigger sides so i know for sure that the chain won't slip off. anybody know where to buy some?
I only have one sheet metal screw in mine....the pic above is Norman's and he used a bolt and a screw.

I have not changed it yet but I did make one out of a MC chain roller and took the bench grinder so the chain would sit in better. So far my stock is working fine but I always make extra parts so when I need them.
 

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jasonh

New Member
Jun 23, 2008
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Well you said that the chain and the tensioner went into the spokes. Adding a screw would've kept the tensioner from going into the spokes. Are you sure the chain slid off is what caused it? The tensioner could've just rotated and taken everything with it.
 

Fosscati

New Member
Jul 3, 2008
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Ocean Shores, NSW
you don't want to drill all the way through the chainstay. Just one side of the tube, and use a sheetmetal screw. I would just do it on the bike so everything lines up.

For a new one, I've heard nothing but good things about the spring-loaded TSC one I linked to.
I would never recommending drilling through the chainstay one side or not - this is a tube (not a bar) and it's structural integrity will be seriously compromised by doing this. We've already compromised the integrity by attaching engines and drive trains to a pedal cycle that was not designed for it to begin with. I very much doubt that the screw idea would provide any defence against the turning moment exerted by a badly aligned chain or a badly attached chain tensioner bracket. The screw would just be pulled up cutting through the tube and destroying the bike frame. Some of those Walmart Schwinns have thinner chainstays than their more expensive cousins in the cycle shops and not only is the chain stay probably inferior but the tube diameter is too small for the tensioner bracket to be properly clamped. A poorly clamped bracket probably caused the accident to happen in the first place. Yes spring loaded tensioners are better but much depends on how the whole thing is set up and how good you are at getting it to the best possible alingnment.
If you stick with the stock tensiners that come with the kits I recommend always having the nylon chain guide at its lowest setting because the bolt is a stepped bolt and hard to replace with a non chinese-made one. We all know that the threads on these chinese bolts can strip and are really made from very mild steel. If you take enough care in getting it right you can tension the chain by sliding the bracket back along the chainstay. When you get too close to the rear sprocket you need to shorten the chain and move the tensiner further out along the chainstay. Usually you can stretch the chain in the first 300 kms and it won't stretch much more after that.
The spring loaded tensioner is best but the stock item can be made to work OK if you have the experience to follow the above guidelines. And yes it is a total piece of crud and a death trap because on the HT if the chain goes too slack it can get sucked into the chaindrive sprocket chamber where it kinks against the first corner and locks the back wheel totally (where the left hand top bolt goes) and send you on a trajectory towards the road in front. Beware of a slack chain on the HT and also of a too tight chain if you want to avoid serious injury.
 
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old motorbike

New Member
Sep 21, 2008
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When I first built mine I didn't like the tensioner so I got a piece of band iron and made a full length one that can't fail. I could have made it nicer, but I went with SBPs shift kit.
 

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Ghost0

New Member
Mar 7, 2008
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Bellingham, WA
I too had used the stock set up and never had a problem. Here are two tips above what had been mentioned. Your chain stay is typically not parallel to the chain. This would suggest that you need to twist the roller so it runs in line with the chain and not sideways. The other tip is to have the chain run on the bottom instead of the top side of the roller. That way if it slips it will slip to the outside of the bike and not into your spokes.
 

toytime

New Member
Mar 20, 2008
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Ontario
I had the same thing happen to me the very first time I tried to start mine. It happened three times in a row until the wheel was shot. I ended up removing links and eliminating the tensioner as well and would just slide the wheel backwards to adjust the chain. On the other hand, when I put the kit onto another bike, I went the other way, with the tensioner and drilled that hole in the chainstay and never had a problem.
Having thought about it a lot, I think this issue may arise when the top chain is too tight by one tooth on the sprocket, if that makes any sense.
 

DOC BOLM

New Member
Aug 21, 2008
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Mississippi
I drilled a hole in the tensioner,ran a 1/4x24 tap in it and used a set screw to lock it in place to the frame,you can get the set screw that is sharp on the end.HD
 

Fosscati

New Member
Jul 3, 2008
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Ocean Shores, NSW
I too had used the stock set up and never had a problem. Here are two tips above what had been mentioned. Your chain stay is typically not parallel to the chain. This would suggest that you need to twist the roller so it runs in line with the chain and not sideways. The other tip is to have the chain run on the bottom instead of the top side of the roller. That way if it slips it will slip to the outside of the bike and not into your spokes.
The only way you could achieve this is by reversing the bracket so it is on the inside of the chain between the chain & wheel with the roller on the outside but that would mean putting the bracket at an angle and inviting serious trouble. If the chain wants to jump off the tensioner then something is seriously wrong with your drive chain alignment, your chain itself, the sprockets or the tensioner or a combination of the above. On the HTs the drive sprockets are engineered by rice farmers and are notoriously uneven. It pays to work on them with a file to try and get the teeth evened up a bit before installing the motor. On all the kits the rear sprockets are not perfectly round and will always cause a bit of horizontal deviance in chain tension as they revolve. Sideways distortions can be corrected when mounting the rear sprocket by adjusting the bolt tensons but the up & down distortion can't really be corrected.
 

tyrslider

New Member
Sep 26, 2008
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RainCity
The stock chain is scrap don't use it, there are many quality chains in the right size. The "rubber donut" sprocket mount is a practical joke. It can and does work but it is such a poor design. The chain tensioner can be omitted if you can get your pedal and drive chains to tension at the same axle adjustment.

Good chain doesn't stretch much (I've never removed links from any chain after it's been mounted).

Rigid/mechanically mounted (not sandwiched) sprockets are the way to go; they spread the load over all the spokes instead of one side.

Chain tensioners as ghosto said need to be in line w/ the chain, sprung or not. And really aren't necessary w/ quality chain and maybe 1/2 links!

There are many solutions!
 
Sep 20, 2008
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web.tampabay.rr.com
The stock chain is scrap don't use it, there are many quality chains in the right size. The "rubber donut" sprocket mount is a practical joke. It can and does work but it is such a poor design. The chain tensioner can be omitted if you can get your pedal and drive chains to tension at the same axle adjustment.

Good chain doesn't stretch much (I've never removed links from any chain after it's been mounted).

Rigid/mechanically mounted (not sandwiched) sprockets are the way to go; they spread the load over all the spokes instead of one side.

Chain tensioners as ghosto said need to be in line w/ the chain, sprung or not. And really aren't necessary w/ quality chain and maybe 1/2 links!

There are many solutions!
I agree 100%...

These kits are inexpensive, spend a little more to upgrade the things that need to be upgraded, from the beginning, and save yourself a ton of grief!

Jim