Motorized Bicycle Chain Tensioner

i was searching on here today and found a spring loaded chain tensioner post. let me see if i can find it again, brb

Comrade Alfonzo said:

I have one of the stock tensioners with 4 bolts and it enjoys playing in my spokes. Does anyone sell a tensioner that has 2 brackets for mounting. I really don't want to drill thhe frame. 10months of work ends with an eighth mile of run time and a ruined wheel.

Click to expand...

It does not have 2 brackets but it looks good, I bought mine today.


Here are the part numbers from Baja Motorsports, that will make it easier to find on the TSC website.

Baja Motorsports Chain Tensioner Assembly
SKU 551023899 $9.98

Baja Motorsports Spring Tensioner
SKU 551025499 $2.98

I've been using that setup on my 4 stroke, It's been working great!

I think (and that could be dangerous)
If you set up the tentioner so that it is hinged to pivit,,, yet have a stop built into the botton so that it cannot spring down past normal setting ,,and a safty bar that is attatched to the pivet bar/wheel that extends below the chain stay and above the seat stay on the out-side ,and can move w/the tentioner wheel,,,,add a spring from the tention wheel piviting bar to the seat stay,,,,,,It looks good in my idea note book,and solves the chain allowing too much slack when starting the motor ,and keeps the tention wheel out of the spokes w/the safty bar ,while keeping spring tention against the lower chain playing while moving foward !!!

corgi1 said:

I think (and that could be dangerous)
If you set up the tentioner so that it is hinged to pivit,,, yet have a stop built into the botton so that it cannot spring down past normal setting ,,and a safty bar that is attatched to the pivet bar/wheel that extends below the chain stay and above the seat stay on the out-side ,and can move w/the tentioner wheel,,,,add a spring from the tention wheel piviting bar to the seat stay,,,,,,It looks good in my idea note book,and solves the chain allowing too much slack when starting the motor ,and keeps the tention wheel out of the spokes w/the safty bar ,while keeping spring tention against the lower chain playing while moving foward !!!

Click to expand...

ive tried adjustable ones my advice dont bother even with a stopthe forces involved would cause problems use a solid mount.. theres no real solid way to garan tee other than drilla hole though tthe stock one though your frame or to weld a tab with a sliding hole..

a bold on one is dangerouse i found that out mine went into my spokes luckily i was only doing 5 mph if i was at 25 i would be dead...

im also looking at a shimaro derailer spinner thingie it has plastic teeth maybe that would be better who knows i got a free one from a bike shop today im going to see how it works

has anyone tried putting rubber around the chainstay tube. my tensioner used to move around too. i wrapped the tube with rubber and now no more moving.

dan1150 said:

has anyone tried putting rubber around the chainstay tube. my tensioner used to move around too. i wrapped the tube with rubber and now no more moving.

Click to expand...

i woulndt i tired it and mine went into the spokes rubber even though tightend down will move.. but your best bet even though it will mar your frame is use the thing like stock and drill a hole though the center though your frame that way it will never ever go into your spokes.. these tensioners are pieces of you know what ive seen other methods like sprokets used etc i just cant find the thread where a guy did it

anybody tried this?

Seriously, I've gotten rid of the tensioner all together amd just shortened the chain to a perfect length and it works WAY better than the cheap tensioner that came with my kit.

seriously! i'm not sure why people are so adamant about keeping something that keeps tearing apart their bike.
the only benefit i see for using one is so they don't have to take the time to mount & shim the engine to get the proper tension.

keeping an idler pulley that keeps trashing your bike is like being in an abusive relationship.

decoherence said:

seriously! i'm not sure why people are so adamant about keeping something that keeps tearing apart their bike.
the only benefit i see for using one is so they don't have to take the time to mount & shim the engine to get the proper tension.

keeping an idler pulley that keeps trashing your bike is like being in an abusive relationship.

Click to expand...

I agree except there is some bike frames that simply do not offer chain clearance at the rear stays with out the use of the teinsoner.

There is interference issues w/some frames as Goat mentioned, there is also those that ride so constantly that "to take the time to mount & shim the engine to get the proper tension" simply isn't a feasible or even reasonable option.

For example I just replaced the #41 chain on my beater, which means ofc that for the next week or more I'll need to readjust the tension frequently as the chain and the sprockets wear into each other ("chain stretch" as it's otherwise known) and even after things settle in and despite the fact it's a heavy duty industrial chain, I ride constantly - enough that a minor chain adjustment/tension is required roughly once a month.

So, as potentially problematic as a tensioner/idler may be, honestly I simply can't imagine how messing around with shims to remount the engine & all that entails (critical stuff like chain/engine/frame/tube alignment, fastener torque & safety etc) just for frequent yet minor chain maintenance is in any way practical - TBH I can only see that as a solution for bikes that just don't get ridden very often and one that has it's own hazards as well.

In fact one of the few things that's irritating with my other build, one w/a shift kit & 3sp hub is the lack of such easy chain adjustment an idler provides - while it has 1/2 links and horizontal dropouts so chain adjustment is still pretty simple (don't hafta mess w/engine mounting), I still need to reposition the rear wheel to adjust, which means I hafta double check wheel/frame alignment and axle nut torque (safety issue again) and might even need to add/remove a 1/2 link - all of which is obv more involved than simply loosening one nut, moving it up a hair & retightening it.

So, while obviously this is a personal preference and whatever works for you is defo good enough - stuff like chain routing and idlers is so specific to individual frames and the rider's usage there simply isn't only one "correct" answer, wondering - even telling people to not run an idler based only on your experience with your bike is hazardous, you simply can't know what's best for them.

In fact I think there's a thread about such lol http://motorbicycling.com/f11/chain-tensioner-suggestions-11815.html

BarelyAWake said:

.
- even telling people to not run an idler based only on your experience with your bike is hazardous, you simply can't know what's best for them.

Click to expand...

with all due respect he has had the idler go into the pulley @ least twice.
there have been many people that have made a thread with the same problem.
i have yet to see someone make a thread about that they got an idler pulley in their spokes that wasn't running one.
so from just history of the OP or the forum, it is more dangerous to run an idler than take advice to not run one.

the thread you linked has good information.
it could be helpful to a lot of people.

it just that it makes me sad to read about all the many spokes broken from the pulley.

decoherence said:

with all due respect he has had the idler go into the pulley @ least twice.
there have been many people that have made a thread with the same problem.
i have yet to see someone make a thread about that they got an idler pulley in their spokes that wasn't running one.
so from just history of the OP or the forum, it is more dangerous to run an idler than take advice to not run one.

the thread you linked has good information.
it could be helpful to a lot of people.

it just that it makes me sad to read about all the many spokes broken from the pulley.

Click to expand...

not if you put a bolt right though it though your frame or weld it it wont go no where now tensioners with springs just as bad

decoherence said:

with all due respect he has had the idler go into the pulley @ least twice.
there have been many people that have made a thread with the same problem...

Click to expand...

...and no offense to anyone, but I hafta wonder about the repercussions of an inexperienced builder constantly messing with their motor mounts & engine positioning in lieu of what could be a far simpler solution.

Granted, the stock, kit supplied tensioner can be a hazard if not installed securely as it's a questionable design at best - yet there's such a plethora of easy options and alternatives that it's really not an "all or nothing" thing (as depicted in http://motorbicycling.com/f11/chain-tensioner-suggestions-11815.html )... I'm prolly gonna jinx myself here lol - but I've been running the stock tensioner (four bolt) for about 10,000 miles w/o a problem, the only thing I've done save adjust it is replace the roller w/one that has bearings in it *shrug*

It's just that every time someone mentions idlers of any sort, there's those that immediately state they're simply not necessary... which honestly is debatable, even unknowable... and the consequences might be even worse.

If someone is having repeated problems with their idler, odds are there's a problem with it's installation & figuring out what that problem might be is far more helpful than just saying they're useless - even if they end up choosing to run w/o one. Chain too tight? Off center sprocket? Idler out of alignment? Incorrectly torqued/low quality fasteners? These are some of the causes of idler failure, interestingly they're the exact same hazards involved with engine mounting - if left unaddressed with a tensioner suggestion, it's likely they'll be problematic with engine mount/adjustment as well...

BarelyAWake said:

...and no offense to anyone, but I hafta wonder about the repercussions of an inexperienced builder constantly messing with their motor mounts & engine positioning in lieu of what could be a far simpler solution.

Click to expand...

well the repercussions of running an idler pulley already happened twice to him.
if the poor guy shot himself in the foot twice i would advise him to give up guns.
instead of trying other guns till he doesn't shoot himself.
i rather an inexperienced builder take their time mounting their engine & adjust both chains.
it is the simpler way than having them try to hodge podge an idler stay. like they are doing on the first page of this thread.

Comrade Alfonzo said:

I have one of the stock tensioners with 4 bolts and it enjoys playing in my spokes. Does anyone sell a tensioner that has 2 brackets for mounting. I really don't want to drill thhe frame. 10months of work ends with an eighth mile of run time and a ruined wheel.

Click to expand...

I never use any chain tensioner. They always want to play in the spokes..
I use an aluminum tee shirt..
A spacer made of aluminum plastic or anything else that wiispace the back of the engine one half chain link forward.

Look at post number sixteen by MotorbikeMike.

http://motorbicycling.com/f3/chain-tension-help-99-2.html

The ceapest and easyest solution is to use an old handlebar grip that you had to remove to put the kit grips on. Cut the end off then split it to fit the bar that your tensioner is on. Put your tensioner over this and tighten. I don't know what these grips are made of but they really stick to metal. Once done the tensiner would bend before it would move. Cost .....ten minutes work.