HELP !!!!!Frame is too thin for chain tensioner mount

M

Motorbikenewb

New Member
Greetings fellow motorbicyclists,

I'm 100% sure this question has already been asked, but I can't seem to find a thread dealing with this, so I'll create a new one.

I installed a Flying horse 66/80cc kit (from bikeberry), on a cruiser bike I bought from walmart. I had no issues with the build except for installing the chain tensioner.

The bar that runs between the rear wheel sprocket and the main center sprocket is a bit too thin. I tried to tighten it so that there is no play, but i won't tighten any more and there's still a ton of play.

I've heard horror stories about the chain tensioner going into the spoke while the bike is being ridden, so I'm aware of the risk, and I want to do this thing right.

This is my 3rd build. Any advise would be greatly appreciated.

:-||
 
I'd start looking into shimming it.

I think I've seen advise to not use, for instance, cut strips of old inner tube. But I don't remember just why that's a bad idea.

You might try leather shims. An old belt would work.

Or perhaps weldable steel strips like you'd get at a home improvement store. Lay it across the jaws of a vise and place a socket (or something cylindrical) on top and pound on it with a hammer to get the curve you want.

My ideas are starting to run out. With a little time I could probably come up with more. But I'll bet you get the idea. I'm sure you can come up with something.

Best of luck.
 
I tried a strip of rubber and duct tape over it. DIdn't work. Still wasn't stable. I'll try the leather shim if anyone can confirm it works. I thought of drilling a hole through the tensioner mount and thru the frame and securing it with the appropriate sized bolt and nut. But I'm not sure how it would affect the frames integrity at that point.

Keep em coming, and thanks....
 
Don't drill the chain stay (the bar that runs between the front and rear sprocket) the bike will crumple.

Try the leather, it's better than rubber.

Or better yet, make a bar that runs between the chain stay and the seat stay from hardware store parts and be safe.

Do not drill holes in that weak frame.
 
I'm with sioux on this.
Beat some of the curve out of the tensioner plates until they fit tightly on your frame. Shimming with rubber or leather is asking for disaster. Even better, have it tack welded once it's installed for better security. Most muffler shops will do this for a few bucks if you don't have access to a welder.
 
I have a friend his moter mounts ws as tight as it could get you could move his moter with eas so we took his mounts to a place that welds exhaust pipes and had them weld a few beeds in the curved parts and it worked out great on his might work on the tentioner
 
The safer tensioners have a strap going from the upper seat stay to the lower chain stay.
Look at the first and second photo examples in this thread:


The cleanest looking are these ones, http://www.jnmotorsbikes.com/product_p/jnm1233.htm

Just be sure that the chain will not rub on the chain stay. Sometimes a tensioner must be mounted on the chain stay, right near the rear wheel sprocket to keep the chain from rubbing on the frame. It depends on how your frame is made and the size of the rear sprocket.
 
OK your third build. Trust me this is not beyond you, if your patient and take your time you will be pleased. I'm starting # 14. I have not, nor ever will I use kit supplied tensioners. The very 1st thing I do after Engine prep is to Mount the sprocket Rag Joint or clamshell on rear wheel and mount the wheel.

If your bike is a beach cruiser with a slide in rear wheel, mount your wheel straight centered and happy with your pedal side chain. Just snub it in place.
Keep in mind ideally you want your wheel axle at least midway in your frame tangs. I have found that if you replace the 22 tooth wheel sprocket with a 19 tooth (or smaller) that will gain you chain length as well as/or a half link (connecting link) on pedal side. Adding more than 1 link always seems to be too much and you don't know if you need to do this yet. As for now don't change a thing. But keep all this in mind as they are your only pedal side adjustment options. I have had good luck with a 44 chainring and a 19 tooth wheel sprocket. Once again -As for now don't change a thing. Just snub your wheel in place,then MOCK in the engine. Loosely bolt it in and check its fit in the frame level.

Now Motor side. You will need to "fit" this chain at this point and will more than likely need a chain breaker.
Loosen Engine mounts front and rear. just loosen them for now. Thread your motor drive chain thru the sm sprckt on the engine to the rear drive sprocket on the wheel with both loose ends meeting in the middle of said drive sprocket. With luck ?? your current set-up will allow you to find a breaking point in the motor chain which will be a loose fit only requiring an engine mount adjustment (shim). If you find the ideal place to join your chain ends will be too tight you have 3 options.

1. a half link or a connecting link (properly called) to lengthen the chain or
2. a shorter rear motor mount. or...
3. both of the above.

Kit supplied 415 chain is good but, I can't find half links locally so I use #41 machine chain. 20 bucks a box at Tractor supply, enough to do 2 bikes. This chain is wide and will give good lateral alignment forgiveness you may need. Also you get 1 Master link with the chain and and connecting links at
the same store. Actually I have found Lowe's and Home depot carry #41 chain, links and pieces.

So here is my assortment of modded rear motor mounts and shims which have kept me safely mounting and motoring. Remember if you mod your rear mount you will have to re-do your front mount too! I hope I have shed a little light on this subject If only to assure this can be safely done with patience. All questions, comments and contributions are of course welcome.
 
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Thanks for all the feedback. I made a leather shim from a belt and used it on one plate and its on good now. No play whatsoever. To be safe, I replace the nuts, bolts, washer and locking nuts with grade 8 replacements. Here is a pic of the build. Not gonna start it today though :-).... don't wanna burn up all my fun in one day.

dance1
 

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You should attempt to pull the tensioner out of line AS HARD AS YOU CAN.
If it moves AT ALL, you are asking for a ruined wheel and possible hospital time.
This part needs to be bulletproof for reliability. A leather shim will NOT keep it as tight as it needs to be.
Be VERY careful on your first ride.
 
Might want to check out Turbobuick1's tensioner.......it would safely solve your issues.

Good luck!
 
The kit supplied chain tensioner and the spark plug boot are the two weakest links in the 2 stroke engine kits.

The only real safe way to use the kit tensioner is to weld it to the chain stay or build a bridge type bracket that spans the seat and chain stay. Relying on clamping only is a recipe for disaster. Most newcomers to this hobby do not realize or anticipate the force that is applied to the tensioner wheel and bracket when under load by engine power.

There is another school of thought that says to drill through the bracket and chain stay and bolt the two together. Although I've yet to see evidence of structural failure using this method I no longer recommend it due to the possibility of a novice drilling a much too large hole that could compromise frame integrity. Weld it, or span the two main frame members.

Better yet, try to get away without using a tensioner if at all possible. But as many of us know that will rely on frame design.

Tom
 
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