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2 Stroke Bicycle Engines & Kits 2 stroke engine kits need careful installation and setup, find out how from our professionals here!


chain falls off

2 stroke engine kits need careful installation and setup, find out how from our professionals here!


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  #1  
Old 07-01-2010, 02:47 PM
remnant remnant is offline
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Default chain falls off

ok my 12 yr old son has a new sky hawk motor on a new bike cant keep the chain on it , seems to have proper tension also cant kick start it with peddle like mine he must peddle off and develop speed . engine acts like it has the compression of a 500 cc 1 lunger , that's why its not capable of kick starting with peddle. chain alignment seems good also, has only run it about 10 min. and 100 yrds between chain pop offs. thanks for any help. ready to crush the ---- thing nearly, bike is a 99.00 delmar schwinn 26"
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Old 07-01-2010, 03:06 PM
freewheeling frank freewheeling frank is offline
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Default Re: chain falls off

sounds like maybe the chain is too tight and binding,hope this helps,frank
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Old 07-01-2010, 03:22 PM
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Default Re: chain falls off

Look down the chain to be sure the run is straight. About 3/4" of free play at the middle of the top run.

Also, on some bikes, you have to twist the tensioner slightly so it runs true with the chain.
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Old 07-02-2010, 12:42 AM
remnant remnant is offline
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Default Re: chain falls off

He finally got it right; thanks so much. It was the tensioner that just needed adjusting and it took a lot of different tries to get it right! He did get it and spent about three hours riding his new bike in the field by our house.
Thanks again
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Old 07-02-2010, 02:26 AM
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bairdco bairdco is offline
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Default Re: chain falls off

as far as "kick starting" it goes, i haven't had a bike that does that yet. i have three of the same motors, and all of them require a different starting method. one you can just roll it out into the street and it fires right up, one takes 20 feet of pedaling, and one takes a half a block.

they all run great, they're just different.
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Old 07-02-2010, 06:29 AM
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Default Re: chain falls off

Welcome the the forum Remnant. This might be an interesting read for you. Cheers
http://motorbicycling.com/f11/chain-...ons-11815.html
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Old 07-02-2010, 10:09 AM
KCvale KCvale is offline
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Default Re: chain falls off

I never use a tensioner on the motor chain.

The reason everyone does is because the kit comes with one and suggests you use it on the chain that came with the kit as that is what you are already working on.

But think about it.
A tensioner is not some crucial part that needs to be on, it is a fix for a simple chain length mismatch problem.

Fix the actual problem and you don't need a fix for the symptom.

This is the Grubee GT1 bike and GT2B motor bike I am almost done with.



I used a 1/2 link on the drive chain and got to only about 8mm to long.



Then I put a flat shim between the motor and the seat post mounting block to take out the motor chain slack.



For shims I just use what I have plenty of, the slot covers on computer cases. After 27 years of building computers I have a box full.



I just fold it in half and put some thin packaging cardboard pieces in between until I have the thickness I want and put in it. As a bonus the little lip on it keeps it from falling through;-}

But even if you don't want to mess with that, at least consider putting the tensioner on the pedal side.



You don't need to use a big ugly heavy duty bolt on tensioner either.
Your pedal chain hardly gets any use and simple little bicycle tensioner will work fine.

If tensioners were a good thing on a motor driven chain, all motorcycles would have them right?

It is a little more work, but in my book worth every minute of it to avoid an un-needed moving part in the main drive so I do that on everything I build.
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Old 07-02-2010, 10:29 AM
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Default Re: chain falls off

I defo respect yer ingenuity & agree with what you've said with only some small additions...

Unfortunately some frames require the use of a chain tensioner to redirect the drive chain because of chainstay clearance issues, there's also some frames that have near vertical dropouts & even with 1/2 links it's not always feasible to try and get a "perfect" length due to "stretch".

But I wholeheartedly agree that if you can manage w/o one - it's far better
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Old 07-02-2010, 06:24 PM
KCvale KCvale is offline
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Default Re: chain falls off

Quote:
Originally Posted by BarelyAWake View Post
I defo respect yer ingenuity...
Thanks ;-}
It is nice to have a new second business with plenty of room for improvement with a little thought.
And of course experimentation, I think I like that best ;-}
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Old 07-02-2010, 08:46 PM
Creative Engineering Creative Engineering is offline
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Default Re: chain falls off

I'm done!!!

I did this over a year ago, (and posted the "how to"), and no one responded.

KC...I wish you the best in your business endeavor!

Jim
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