chain tensioner keeps moving! please help

[screamthepoetry]

i just finally got the thing ready to turn over but every time i go to fire it up the tension pulls the tensioner down into my wheel and either catches a spoke or pulls the chain off the sprocket.. i dont know what to do, i have tried everything i can, its steel so i cant drill through the mount to mount it directly to the frame, i have done everything i can to fill the space securely for the tensioner so that it wouldnt move.. this is really upsetting someone please give me a quick fix

 

[F_Rod81]

Something like this should help. . . hope it works for you

Chain tensioner mod

 

[BarelyAWake]

http://motorbicycling.com/f11/chain-tensioner-suggestions-11815.html

 

[Mozenrath]

Make sure your sprocket doesn't "wobble" when the tire spins.

You can also put something like double-sided tape on the frame where the tensioner is installed.

 

[wheelbender6]

This may be inside one of those links but I couldn't open them. Drill and tap a hole in the side of the chain tensioner bracket so that you can thread in a bolt against the chain stays of the bike frame. When the bolt tightens against the frame, it prevents the tensioner from rotating or sliding aft.

 

[screamthepoetry]

see thats the problem i cant drill a hole in the tensioner, i want to so i can just mount it directly to the frame but i cant, and i have already tried the double sided tape as well as foam, and rubber to keep it from swaying, it stays snug enough so i can pedal with the clutch engaged but as soon as i disengage the clutch to fire it up it yanks the tensioner into my wheel..i have tried about everything, and dont have the tools to drill a hole in the tensioner, i know my drill wont be able to pull it off.

 

[rohmell]

Two things you can try:
1: Squeeze the curved tensioner pieces in a vise to make them flatter.
2: cut an aluminum soda or beer can into strips that can be wrapped around the stay to build up its thickness.

 

[nightcruiser]

Best way to fix your chain tensioner is to get rid of it! Shorten chain, adjust motor position and rear wheel position until you have enough tension to run without the tensioner... I had nothing but problems with mine too... Before every ride, mess with the tensioner, and every ride listen to the tensioner... Screw the tensioner! After I got rid of mine I never once had to think about my chain again....
My mountain bike frame didn't give me any room for adjustment of the rear wheel, so I had to make a steel spacer to put under the rear motor mount to move the motor ever so slightly away from the rear wheel. I just used a section of flat steel stock, drilled holes to match the motor mount and inserted it between the motor and the mount. Then when I mounted the motor, I installed the chain before I tightened down the motor, and set the motor orientation so it put enough tension on my chain to ride without the tensioner. I still have a little more slack in my chain than I did when I ran the tensioner, but it rides like a dream, never had a single problem. Since I have a tiny 16.5" frame I have very little room for adjustment on the motor position, on a bigger frame I think it should be pretty easy to get optimal chain tension without any tensioner just by adjusting your motor and rear wheel position. If the physics just wont work out you can get half links for your chain...
Trust me, if you setup your bike to roll without the tensioner you will not regret it.....

 

[Mozenrath]

I don't really understand how any of you guys can get away without the tensioner. I haven't tried in a while, but I couldn't get the chain to be taught enough on its own.

I too had trouble with the chain coming off when I first put together my MB. It turned out that the sprocket wasn't mounted entirely accurately, and it appeared to wobble a bit when the wheel spun. All I did was flipped my bike upside-down, spun the rear wheel, and held the tip of a Sharpie marker to the side of the sprocket while it spun. This drew a line on the sprocket in the shape of a circle, but since the sprocket was wobbly, the line didn't draw a perfect circle and in the area that wobbled it was more of an oval. This is a great trick because it shows exactly where on the sprocket the bolts need to be tightened.

Once I got rid of the wobble, I never had the chain come off again. I still have the stock tensioner and I have only had to readjust it once(because my chain stretched). I don't even worry about it going into the spokes.

If you really want to be sure that the tensioner won't move, many people have used bars and springs that connect from the tensioner to the frame to prevent it from moving. You can search this site or my blog for threads where people have modified their tensioners, and there are plenty of threads about that.

 

[screamthepoetry]

i dont think its wobbling, it just when the chain gets tight when going to start it, it pulls the tensioner inwards.. i can hold down the clutch and ride it around fine, rode 2 blocks on it with the clutch engaged because i wanted to make sure it wasnt just working its way off.. but then as soon as i go and disengage the clutch to start it up, it just yanks the tensioner down really hard into the spokes.. i really want to just get rid of the stupid thing, i have looked at it and i dont think i would really need to change anything if i got rid of it other then shortening the chain, my big thing would be, what if i shorten it and then it doesnt work, i gotta put the links back on or get a new chain...its just a pain

 

[2door]

I have some problems with the idea of shimming the rear engine mount to adjust chain tension. The front mount, both front and rear actually, need to sit firmly against the bike frame. That means full metal to metal contact through out the inside curvature of the mount. Shimming the rear of the engine will tilt/relocate the front mount so it cannot sit as designed. Add to that the fact that as the chain and sprockets wear the chain tension will need to be adjusted. That means adding more shim to the engine thereby increasing the misalignment of the front mounts ability to saddle the downtube correctly.

There are other options available such as building a tensioner mount that spans the chain and seat stay or drilling the mount and frame for a small bolt/screw, welding the mount to the frame or relying on the rear drop outs for chain tension adjustment and running without a tensioner if you have the frame to chain clearance to do so.

Because of the varities of frame designs out there and the necessity to sometimes fabricate special brackets, mounts, parts etc. This hobby requires that the builder owns or has access to certain tools and equipment. Except in some cases installing a successful and reliable engine installation on a bike is not a bolt-together hobby. Some skills and tools are going to be necessary. This isn't like going to the local motorcycle shop and buying a factory designed and built vehicle. Much of it is DYI and that means having the right tools. A pair of pliers and a screwdriver just ain't gonna do it. Sorry, but that's just the facts.
Tom

 

[F_Rod81]

Much of it is DYI and that means having the right tools. A pair of pliers and a screwdriver just ain't gonna do it. Sorry, but that's just the facts.
Tom

Well put my friend!

 

[screamthepoetry]

i have tools, i just dont have the right kind of drill that will get through a steel plate, i found too small plates about 2 1/2 inches long that i was able to bolt to the top of the tensioner plate with longer nuts, and then bolt them diagonally directly to the frame, seems to be solid and not going anywhere, but wont know until i get up tomorrow to test drive it

 

[nightcruiser]

i dont think its wobbling, it just when the chain gets tight when going to start it, it pulls the tensioner inwards.. i can hold down the clutch and ride it around fine, rode 2 blocks on it with the clutch engaged because i wanted to make sure it wasnt just working its way off.. but then as soon as i go and disengage the clutch to start it up, it just yanks the tensioner down really hard into the spokes.. i really want to just get rid of the stupid thing, i have looked at it and i dont think i would really need to change anything if i got rid of it other then shortening the chain, my big thing would be, what if i shorten it and then it doesnt work, i gotta put the links back on or get a new chain...its just a pain

If you're using the kit chain it is such crap that links come out like nothing.... And sooner than later, if you weigh more than 150lbs, you're probably gonna have to mend the chain anyways...
If you have upgraded your chain already to something more sturdy, then dig up the old kit chain and shorten it for a test fit, if it works out then adjust your real chain...
What is more of a pain, a tensioner in the spokes or messing with a chain a bit???

 

[nightcruiser]

I have some problems with the idea of shimming the rear engine mount to adjust chain tension. The front mount, both front and rear actually, need to sit firmly against the bike frame. That means full metal to metal contact through out the inside curvature of the mount. Shimming the rear of the engine will tilt/relocate the front mount so it cannot sit as designed. Add to that the fact that as the chain and sprockets wear the chain tension will need to be adjusted. That means adding more shim to the engine thereby increasing the misalignment of the front mounts ability to saddle the downtube correctly.

There are other options available such as building a tensioner mount that spans the chain and seat stay or drilling the mount and frame for a small bolt/screw, welding the mount to the frame or relying on the rear drop outs for chain tension adjustment and running without a tensioner if you have the frame to chain clearance to do so.

Because of the varities of frame designs out there and the necessity to sometimes fabricate special brackets, mounts, parts etc. This hobby requires that the builder owns or has access to certain tools and equipment. Except in some cases installing a successful and reliable engine installation on a bike is not a bolt-together hobby. Some skills and tools are going to be necessary. This isn't like going to the local motorcycle shop and buying a factory designed and built vehicle. Much of it is DYI and that means having the right tools. A pair of pliers and a screwdriver just ain't gonna do it. Sorry, but that's just the facts.
Tom

Perhaps you didn't read my post carefully, I put a steel shim BETWEEN THE MOTOR AND REAR MOTOR MOUNT. The mount itself seats against my bike post just as it did originally, tight around the post with nothing between the mount and post. Since all frames are a bit different, the angle needed on the front mount is rough at best for most frames, this little shim I added has not effected how the front mount contacts frame, if anything its better.
I had made two shims, tried it with two and the chain was a bit tight, backed down to one and I am golden. I run a #41 chain straight from the motor sprocket to the wheel sprocket, I don't know how much more prefect than that you can get. The radical angles I see some people running on their chains from the tensioner is what gets me wondering WTF...
Trust me, my bike is a whole lot more solid with this tiny shim and no tensioner....

 

[BarelyAWake]

There is interference issues w/some frames... and there (are) 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 at least 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.

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

...................

 

[nightcruiser]

...................

I don't know what to say, I never needed to adjust my motor (or chain tension) once it was set right. This #41 chain I have isn't gonna stretch from the force of this motor and my weight, the kit chain is another story. The ANSI chain is pre-stressed and very solid, at least mine is. Apparently my motor mounting is tight as well, cause nothing has moved to effect the chain tension since I mounted it. I put about 1000 miles on the bike this summer, about 900 with this chain and about 800 without the tensioner. (I limped along on the kit chain for about 100 miles, then tried the #41 chain with the tensioner for about 100 miles, then right away rid myself of the tensioner) Initially I had thought perhaps after things settled in I might need to add the second shim, but that never happened.
Bottom line, it seemed I was messing with the damn tensioner every ride, since I got rid of it I have NEVER had to touch my chain once. I realize some frames will not allow a direct chain route due to interference with one thing or another, but if you can get a clean shot from sprocket to sprocket I recommend you give it a try....
I was all hot to design a neat spring loaded tensioner, that all went out the window, no need to bother....

 

[Tacomancini]

If you have to use a tensioner, swap the mounting hardware with grade 8 nuts and bolts from home depot. Otherwise you can't tighten the tensioner mount enough and the bolts will likely strip. Swap that stuff, tighten it to death, knock it around with a plumbers pipe wrench to make sure it's not budging, then use the plumbers wrench to put a slight twist in the tensioner to better match the chain direction. If it holds with the leverage of the plumbers wrench, then it should be fine under the stress of the engine. But hec yeah, swap that chain with quality #41 chain.

If you can ditch the tensioner, that is by far the best method. If you decide to utilize the tensioner the upgraded mounting hardware is a must.

 

[2door]

Whenever this subject comes up there's going to be differences of opinion. The tensioner verses the no tensioner crowds are never going to agree.

I will say this; The term "chain stretch" is a misnomer. Chains don't stretch, no matter the brand or quality, they wear. As do sprockets. I too replace all kit supplied chain with a quality, industrial grade #41, but, over a period of time, regardless of your riding style, body weight, touque values, lubrication, or any one of several other factors, the chain and sprocket teeth WILL wear. As this occures the chain tension will decrease necessitating tightening, or adjusting something to get back to the proper tension.

If I'm thirty miles from home or even just around my neighborhood and I find that the chain has loosened (worn) enough to warrant adjustment I'd much prefer loosening one single nut/bolt on a tensioner and sliding it up a 1/4" than disassembling my motor mounts to achieve the same results.

Listen to the OP. He readily admits that he doesn't have access to the proper tools to make the necessary modifications to a kit tensioner bracket. He said he can't even drill into the bracket. How is he going to fabricate steel shims?

We offer help to folks but you need to keep in mind that everyone doesn't have what's needed to accomplish modifications and/or upgrades and when that fact is known why complicate his dilemma by suggesting tasks that he's not able to do? Keep it simple when it's obvious that a simple solution is called for.

As far as using or not using a tensioner....DO WHAT WORKS FOR YOU. That goes for every other aspect of this hobby. Just examine the advice you give and who that advice is going to.

Tom

 

[Mozenrath]

Couldn't he just buy a spring and used it to connect the tensioner to the frame? No drilling involved, I think.