(Motorized Bike Kit) Good Chain Tension Setting rear sproket

Discussion in 'Motorized Bicycle General Discussion' started by Lewis, Jun 24, 2014.

  1. Lewis

    Lewis New Member

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    Hello Everyone! My name is Lewis and I'm fairly new to motorized bikes and I hope to help the community in anyway I can!

    Anyway... On to my questions. What would be considered good chain tension?

    I seem to need to true my sprocket at the moment because, I seem to have issues with my chain tightening up then becoming too loose.
    My problem is that I can't seem to get the rear sprocket centered. Any tips or pointers? :-||

    Also I made my own spring loaded chain tensioner which, only works sometimes...
    It has crazy amount of tension but, when I go to dump the clutch the chain gets stuck in the engine sprocket box and I end up burning my tire up and I have to take the clutch arm off and fix the bind chain. .bf.

    I plan on using this bike to go to my job site but, I'm greatly discouraged right now.

    I hope I posted this in the right area. :p
    Thanks for reading!
     
    #1 Lewis, Jun 24, 2014
    Last edited: Jun 24, 2014
  2. 2door

    2door Moderator
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    1/2" to 3/4" of slack. The rear sprocket must be centered on the hub or proper chain tension can never be achieved. I'm not a fan of spring loaded tensioners. They allow slack in the chain when you least want it.

    Make a pointer that is attached to the bike frame. Suspend the rear wheel so it can be spun freely. Aim the end of your pointer at the outer ends of the sprocket teeth, spin the wheel and you'll quickly see which direction the sprocket needs to go to get the teeth concentric with the rear hub.

    I use a plastic head hammer to tap the sprocket, hitting on the teeth to move it. If you don't have a plastic hammer try a piece of hardwood or something similar to protect the teeth from damage while tapping it into position. Or, as will be suggested, purchase a sprocket adapter in place of the kit 'rag joint'. Good luck.

    Tom
     
  3. Lewis

    Lewis New Member

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    Thank you Tom. That was exactly the info I was looking for.
    I'll be sure to upload some pics of the bike in the near future.

    Happy biking! dance1
     
  4. CTripps

    CTripps Active Member

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    Centering the sprocket is a sometimes tricky job. Loosen all 9 bolts before you have a go at it. Tom's technique is a good one... I do something similar, but instead of a wood block I put a left over bit of drive chain in the sprocket teeth, and use a rubber or nylon mallet to tap it to try and move it.

    Toothpicks, matchsticks, or even finishing nails can help when used as spacers to center the sprocket.

    With all 9 bolts and hardware in place, tighten the 'middle' bolts (based on the three backing plates) first. Go evenly, and watch the gap between hub and sprocket. If it gets too small on one edge, loosen that bolt a little and tighten the other two a bit and you should be able to pull it together pretty evenly.
     
  5. Lewis

    Lewis New Member

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    Thanks, you guys are great!

    I never thought of tightening the middle bolts on the plates I think that will help a lot.

    I think I'll try match sticks also. I have a fairly large gap on the shaft and sprocket hole.

    Wish me luck!
     
  6. 2door

    2door Moderator
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    CT's input is appreciated. I forgot to mention that you'd need to loosen the bolts, Duh.

    The reason I use the pointer method instead of trying to center the sprocket hole to the hub is that I've had sprockets that were made poorly and the center hole wasn't exactly centered. You could center the hole to the hub but the outer diameter, the sprocket teeth, weren't concentric to the hub. Naturally those bad sprockets could have been a fluke and most are made better. I just stuck to the pointer method to assure myself that the sprocket was centered.

    Like everything else about this hobby there is usually more than one way to achieve the right results. We just like for a new builder to explore all the options. Good luck.

    Tom
     
  7. Davezilla

    Davezilla New Member

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    I used the spacer method when I put mine on for the first time, but mine was so close to the same size it would have been centered anyway just by eyeballing it... but using a pointer is a really good idea on these in case the hole isn't perfectly centered.
    One other thing I do after I get it bolted down is to check the side to side wobble and adjust it straight by tightening and loosening the 9 bolts until straight, then tighten them all down as evenly as possible once the runout is as minimal as possible. You can fine tune it even more by using a dial indicator, but as long as it's under about 1/16" it won't pop off the chain.
     
  8. 2door

    2door Moderator
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    More good advice. Lewis is getting great help here from you guys. Thanks.

    Tom
     
  9. Lewis

    Lewis New Member

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    It's raining cats and dogs here so I can't ride but, I think I got it. Absolutely no tightening up and then becoming loose! I got as much wobble out that I could (the wheel is not very true). It appears very stable at the moment. I'll let you guys know how it goes when the weather is nice. I don't think the electrical would like the rain. :p

    Yet again. Thanks you guys, you're life savers!

    brnot
     
  10. Davezilla

    Davezilla New Member

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    Same here with the rain... Do you live in Texas by any chance? It's been crazy over here lately, bone dry one day, then pouring the next, then it's dry again a few hours later...

    Now for your chain coming loose, these cheap chains don't come pre stretched so in most cases you'll install one and it'll be loose after a few miles, you tighten it up and 5 miles later it's loose again... and all your adjustment hardware is still nice and tight. I usually set a new chain a little on the tight side because of this and sometimes it'll stretch to where I intend it to be but other times it'll be way loose and I still need to go back in and re tighten it to get the right amount of deflection. Most the time after you adjust it 2 or 3 times it'll stop stretching and keep it's adjustment.
    Most new high quality motorcycle chains come pre stretched so tehy can be installed, set, and they stay that way so this is hardly ever a problem but a new chain that's never been run or pre stretched will need repeated readjustments, think of it like the chain breaking in.
     
  11. Lewis

    Lewis New Member

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    I don't live in Texas unfortunately. I live in New Hampshire. The land of motorized bicycle at least, the part where I live that is. People ride them everywhere here. That's how I learned about them.
    Yeah, the rain comes and goes just like you described it. I think it's the mountainous nature. I'm very surprised how well the carburetor works out here since I'm above sea level quite a ways.

    Anyway...

    I tested my bike out today and it seems to work OKAY. I get a slight tugging from the chain. I rolled the bike and the tension is very consistent. I think I may need to knock out a few chain links? With that being said.
    Where would be a good place to have the chain tensioner on my frame? Like, how should my chain look?
    Should the path from the motor sprocket to the rear sprocket be as linear as possible with little tensioner interference?
    I believe the chain tensioner is WAY to close to the rear sprocket which, gives it the shakes when you're biking at low speeds. It goes away when your biking at a higher rate of speed. I feel that it's so close but, it needs some tinkering still.
    .xx.
     
  12. 2door

    2door Moderator
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    Chain/sprocket alignment as well as chain tension is essential for a smooth running chain drive.

    The tensioner wheel, if you must use one, must be aligned with the chain path. It can not pull the chain off to either side. Most, if not all kit tensioner brackets must be bent, or twisted to achieve this. The bracket as it comes in the kit does not allow for any taper in the chain stay and the tensioner wheel will be angled, not aligned with the chain.

    The other big issue is securing the tensioner bracket so it can not rotate into the spokes. That has caused a lot of problems, both expensive and potentially dangerous for new builders. There are pages of discussion here on chain tensioners. Try the search feature and type in 'tensioner'. You''l have lots to read. Just make sure the bracket can't move. The best option is a bracket that bridges the seat and chain stay.


    You'll want to maintain 1/2" to 3/4" of slack. To measure slack, engage the clutch, roll the bike forward gently until the piston comes up against a compression stroke. At that point the top chain run will go slack. That's the slack to be measured. Too tight or too loose will cause you problems.
    Good luck

    Tom
     

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