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Mounting Techniques for Bicycle Motors Every frame is different. Share and ask questions about mounting your motorized bicycle engine kit to your bicycle frame or bicycle rack


Chain tensioners

Every frame is different. Share and ask questions about mounting your motorized bicycle engine kit to your bicycle frame or bicycle rack


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  #1  
Old 07-12-2008, 12:20 PM
Bikeman08 Bikeman08 is offline
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Unhappy Chain tensioners

Hello world, I really flustered, i need another design for the chain tensioner that one that came with the kit really sucks, get to close to the sprokets gets kinda scary. any ideas. I looked on the site and saw some mods, but i dont know where to get the stuff.
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Old 09-02-2008, 01:35 PM
raptor50 raptor50 is offline
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Default Re: Chain tensioners

bikeman o8
hi i,m raptor50 you are in luck i have the perfect chain tenioner .just finished testing it .an now i,m going to start making them .i also gained about 4 mph with it.e-mail me at snjfrost@sbcglobal.net
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Old 09-02-2008, 02:51 PM
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mralaska mralaska is offline
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Default Re: Chain tensioners

The best thing I have done on my bike so far is remove the chain tensioner. One link is about 1 inch so you only need a half inch of engine movement to fully adjust the chain. I made three shims out of 1/8 in flat aluminum stock which gives me all the adjustment I will ever need. I cannot remember who I got the idea from, but he called the inserts 'T Shirts' because of their resemblance. Just loosen up the engine and drop them in place. If the chain gets too long just remove a link and start over again. The chain runs much smoother now and no more messing with the tensioner or worrying about it rolling into the spokes again.

Edit: I forgot to mention that you may need to lengthen your rear engine mount studs. I made mine longer when I replaced all the studs but I do not remember how much longer I went. I made the longer studs out of m6x1 8.8 threaded rod from mcmaster.com. The shim stock I got from the bin in a hardware store. I think it was an Ace but most hardware stores have it. With a sharp hacksaw blade and a vice to hold it in place you can whip them out in less than a minute each.
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Last edited by mralaska; 09-02-2008 at 04:02 PM.
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Old 09-02-2008, 04:11 PM
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Bikeguy Joe Bikeguy Joe is offline
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Default Re: Chain tensioners

Here's a tip I discovered....put the tensioner wheel on facing outward, that way if the 'chain pulls the tensioner" it pulls it AWAY from the wheel.

That's usually caused by the chain being too tight.
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Old 09-02-2008, 04:16 PM
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ebmvegan ebmvegan is offline
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Default Re: Chain tensioners

Live Fast Motors has a spring chain tensioner. They don't have a pic of it but We had installed it on 2 bikes and they work great.

Livefast Motors: Bike Motors - Accessories

It doesn't look pretty but with the chain guard, you don't even notice it.
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Last edited by ebmvegan; 09-02-2008 at 04:17 PM. Reason: misspelled
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Old 09-02-2008, 07:14 PM
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Saddletramp1200 Saddletramp1200 is offline
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Default Re: Chain tensioners

I mounted my stock tensioner on the bathroom wall, adds that "homey" touch! My Huffy don't need one, and chains are plentyfull and the chain DAX supplies is a better chain anyway. My frame rails are tiny so it won't hold any how without some welding. It has not streched enough to worry about. (C)
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Old 04-02-2009, 12:59 PM
Jimigunne Jimigunne is offline
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Default Re: Chain tensioners

I have have a cruisier with the 80cc 2-stroke gas engine mod. (the kit that is sold by many dealers on ebay). Am struggling trying to find a workable chain tensioner. Gave up on that stupid nylon roller. I like Saddletramps' idea of just dispensing with the tensioner altogether! But if the cheap Chinese chain is going to be stretching a lot, then one would have to constantly put in thicker shims.
Question is, how much slack do you want on the chain, when pushed in the middle of the longest span, for best performance? 1/2 inch? I am real paranoid about the chain coming up/off from the engine sprocket.... there is no clearance, and I have heard of this breaking the engine shaft keyway. With the stock unworkable nylon roller, and with it set for quite a lot of tension, this was happening. I was only rolling the bike forward with sparkplug removed, clutch pinned disengaged, so it didn't do any damage..... but after moving the bike forward a few feet, the chain started to come off engine sprocket a little bit. It sure jams it up totally! I don't really know why a high amount of tension was causing the chain to start coming off the engine sprocket...but it was. So it seems you can have too much tension, or too little.
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Old 04-02-2009, 01:28 PM
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Default Re: Chain tensioners

Jimigunn,
You are correct. The chain can be too tight or too loose. You want to shoot for 1/2" to 3/4" slack measured at the center of the chain span. As for your tensioner problems do a little research here and you'll find plenty of discussion regarding tensioners. I happen to be a firm believer in them even when using upgraded chain such as #41 industrial chain. Two things you need to watch is proper alignment of the tensioner to the rear sprocket and rear sprocket to engine drive sprocket. I don't like to see much more than 1/4" out of alignment between the engine and rear sprocket but in a pinch 3/8" will work. Most of the clamp-on tensioner brackets will need a slight twist put in them to give you good alignment to the rear sprocket. They are typically straight and the chainstays will have a slight taper so if the tensioner is not aligned you will be guiding the chain off to one side or the other. Many of us have also secured that ugly tensioner bracket to the bike frame with a self tapping screw or a small bolt and nut through a hole drilled completely through the bracket and chain stay. You only need for that bracket to come loose once to appreciate the amount of damage it can do to your rear wheel and spokes. Another good suggestion is to replace the plastic pully with a skate board wheel. You'll need to find a method to cut a groove in the wheel wide and deep enough to allow the chain to pass around it smoothly. Most of the skateboard wheels have bearings instead of those cheezy bushings, they're made of polyurathane instead of plastic and run much quieter. One other thought about your chain coming off; Are you sure your rear sprocket is running true to the rear wheel hub. Lift the bike, clutch disengaged and spin the rear wheel. Watch for wobbles either side to side or vertically and correct any problems there. The sprocket must run concentric to the hub or it can cause the chain to wrap and that can cause all kinds of problems. Get back to us if none of this has cured your ills.
Tom
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Last edited by 2door; 04-02-2009 at 01:30 PM.
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  #9  
Old 12-13-2011, 09:15 PM
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abikerider abikerider is offline
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Default Re: Chain tensioners

Here's the tensioner I just made. Very simple and guaranteed not to twist into the spokes.


Also, it's lighter than the stock chain tensioner!

Last edited by abikerider; 12-13-2011 at 09:24 PM.
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Old 12-13-2011, 09:21 PM
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Default Re: Chain tensioners

Your link is dead. Try again.
Tom
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