Badger 100 Plastic Chain Tensioner

#1
I bought this cheap old Yukon Trail Badger mini-bike a couple Christmases ago for my son and have kept it running despite the fact it is really a cheap poorly manufactured mini-bike. I have finally reached the limit of my mechanical ability (which isn't much) with an issue with the chain continually falling off. There are two plastic chain tensioners as shown in the photo that are fairly worn, but i don't know if that is the issue with the chain not staying on. I have had to lossen the enging mount bolts a number of time and move the engine forward to tighten the chain because the top chain tensioner has worn and due to other issues that have caused the chain to continually come loose. I know the bike is a POS but with a little TLC I've kept it up and running and my boy has had a lot of fun on it. The issue with the chain popping off has got me stumped and my first guess is that the plastic chain tensioners are the problem. There appears to be an issue with the chain lining up properly from the front to rear sprocket through the plastic chaing tensioners. It looks to me like the chain tensioners are causing the chain to bend slightly between the front and rear sprocket.

POS-MiniBike Chain-FullPhoto.jpg

I would really appreciate any advice on how I can get this cheap old mini bike chain to stay on. Does anyone know a good place to buy these types of plastic chain tensioners? Another question I have is if there are any known modifications I could make to this type of chain assembly that would reduce the frequency of the chain coming off of the rear sprocket. The teeth on the rear sprocket seem quite small and I am also wondering if a better chain and rear sprocket might help keep the chain from coming off all the time.

I would greatly appreciate any advice on how to repair and fix once and for all the continual issues we ahve had with the chain staying on this cheap kids mini bike. Other than that the bike runs great. I hope I can get it running again because my son has had a blast on it when the chain has stayed on.

Thanks for any help.

Brian
 

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capguncowboy

Well-Known Member
#2
The bottom tensioner goes below the chain. That should take a lot of slack out of the chain so the top tensioner isn't doing all the work. If that doesn't take all the slack out, you could try removing a link or two.
 
#4
Capguncowboy are you saying that the bottom tensioner shown in the photo if incorrectly positioned above the chain? I'll try to move the chain to being on top of the tensioner, but its hard to imagine how the lower tensioner then would apply any tension to the chain. The top tensioner is above the chain as well currently, but does that need to be under the chain as well?

Does anyone know where I could purchase replacement chain tensioners of this type? The top tensioner is chewed up pretty good. I tried searching around for replacement tensioners, but it was tough to determine from the ones I found online if they were correct or would work for this bike. Appreciate any help with getting some better parts on this to keep the chain on.
 

capguncowboy

Well-Known Member
#5
Yes, that's what I'm saying. The one on top should be on top of the chain, and the one on the bottom should be below the chain -- I can't see the bike in front of me, I'm just telling you what I know from my experience with most tensioners.
 
#6
OK, thanks for the help. That is what I thought you meant. This cheapo mini-bike doesn't have an adjustable bottom tensioner and the one on top wouldn't have the adjustment length to be placed on top of the chain. What I am thinking about doing is something like this photo where a bracket has been used for the bottom tensioner so that the tensioner can be adjusted from the bottom. There is no other way that I can get the tensioner on the bottom to exert upward tension on the chain, because as I mentioned before, the bottom tensioner is not adjustable.

ChainTensionerMod.jpg

Does anyone else have any tips on chain guides, different chains/sprocket sizes, other modifications to the tensioner or otherwise? There seems to be some scattered information on alternative modifications, other more mechanical people than myself have made to similar mini-bikes with these types of plastic chain tensioners to keep the chain from falling off every time it is ridden. Any advice on modifications to the tensioner, chain, sprocket, etc. would be greatly appreciated.

Here is another roller to sprocket modification I came across that seems interesting -

IMG_20121028_114631.jpg
 
#7
The chain shouldn't fall off. You must have something else going on. Make sure the rear wheel is centered in the swing arm and that the motor is straight. Some times the motor bolts come loose and the engine will shift. My badger only came with the top chain adjuster and I haven't had any problems. Use a long stick or yard stick and lay it on the rear sprocket and the clutch to make sure you are straight.
 
#8
Thanks manchester1. I've checked and rechecked the engine alignment, but will double check the rear wheel. I have a feeling that the tensioner configuration on this cheap Chinese POS needs a little modification. I have seen some spring loaded chain tensioner posts on here that look interesting, but need to learn a lot more about them before I would be able to put one together on my own. Most of the spring loaded tensioners on similar mini bikes that I have read about are custom built. Are there any spring loaded tensioners on the market that would work for this bike?

Another question I have is the type of rear sprocket and chain that is on this bike. I know very little about mini bikes and would appreciate any help with identifying the type of rear sprocket and chain that is on this bike. If a better chain and sprocket would help I would consider replacing the ones on this bike. Most of the doodlebug chain tensioner setups I have seen on this forum have one bottom tensioner under the chain that apply upward tension on the chain.

If anyone has any tips on how I could modify the bottom tensioner, which is not adjustable on this bike, with an adjustable and/or spring loaded tensioner I would appreciate the advice.
 

george3

Active Member
#9
If a straight edge from rear sprocket to clutch shows it lined up, then check for ware in the swing arm pivot, see if there is slop, also the bearings in the rear wheel. Pull the chain off and look for kinked chain. If you adjusted it 2 times throw that pos chain away and replace it. While the chain is off spin the wheel and check if the sprocket is bent. 1/8 off is prob too much. Check the teeth on the sprocket for bent teeth. 2 roller guides? bad design. swing arm bikes need jack shafts.
 
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#10
Thanks manchester1. I've checked and rechecked the engine alignment, but will double check the rear wheel. I have a feeling that the tensioner configuration on this cheap Chinese POS needs a little modification. I have seen some spring loaded chain tensioner posts on here that look interesting, but need to learn a lot more about them before I would be able to put one together on my own. Most of the spring loaded tensioners on similar mini bikes that I have read about are custom built. Are there any spring loaded tensioners on the market that would work for this bike?

Another question I have is the type of rear sprocket and chain that is on this bike. I know very little about mini bikes and would appreciate any help with identifying the type of rear sprocket and chain that is on this bike. If a better chain and sprocket would help I would consider replacing the ones on this bike. Most of the doodlebug chain tensioner setups I have seen on this forum have one bottom tensioner under the chain that apply upward tension on the chain.

If anyone has any tips on how I could modify the bottom tensioner, which is not adjustable on this bike, with an adjustable and/or spring loaded tensioner I would appreciate the advice.
FMJ, I am completely new to this forum. I bought a doodle bug about two weeks ago, and the chain kept popping off too. I have never owned a mini bike, and know next to NOTHING about mechanic work. BUT! For about $10, I've already started building my own chain tensioner. It is VERY easy. I did a build thread with photos in it that I'll link right below, so you can see how I'm doing mine.

The steel cost me $5. The only tools I used were a jig saw, metal file, a wrench, and a drill. Very, very simple. Don't be intimidated by the "custom" idea. I'm am totally new to this stuff and I've already built one with about an hour's work. If you have more questions about it, I can definitely try to help, but I'm very new to this stuff, fyi.

http://www.oldminibikes.com/forum/d...hain-tensioner-scratch-pictures-included.html

I'm going out of town today, but if you wanted me to, I could build one for you when I get back if you want to cover the cost of materials and shipping. It would probably be less than $15 for everything. But that's totally up to you.

Hope this helps.
 
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