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Motorized Mountain Bikes and Road Bikes Motorize a full suspension mountain bike to get a smother ride or for a little more speed try motorized road bicycles. This section is for sharing ideas on motorizing your mountain and road bikes.

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  #1  
Old 12-09-2016, 09:00 AM
bigwave bigwave is offline
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Join Date: Dec 2016
Location: South Central Illinois
Posts: 12
Default First build

Howdy all, first build here, found an old MT bike at local bike shop for 20$ in good shape, a "free spirit", it's old enough that it has good bearings that are in holders (don't fall all over when repacking) and bike is pretty solid. My question is this, how critical is chain alignment? By the eyeball method it appears to me that my front engine sprocket and my rear sprocket are off by 1/8 to 3/16" (3-5mm) front to back. Can the chain length and chain tensioner handle that or am I asking for trouble? I can torque the engine a little to "point" the sprockets at each other, is that enough?

Installing a "Flying horse" 66/80cc 2 stroke, silver (a few bearings or something) kit. I'm a shade tree mechanic that will work on anything, and pretty good at it, I service and fix all my own ATV's, work on Jeeps, etc. I'm no pro but understand most things mechanical.
Thanks
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  #2  
Old 12-09-2016, 01:16 PM
TheNecromancer13 TheNecromancer13 is offline
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Join Date: Jan 2015
Location: Portland, Oregon
Posts: 556
Default Re: First build

Chain alignment is important. I found out the hard way that even if the chain alignment isn't off by enough to cause derailments, it will cause the chain to wear down your sprocket very fast. Are you using the stock sprocket adapter? If you use a hub or disc mounting sprocket adapter you can usually get perfect chain alignment with a bit of tinkering. Your spokes will also last a lot longer. Personally I like the disc sprocket adapters better, as they will fit any disc brake mount, whereas the hub ones only fit certain diameter hubs. Also with the disc adapters you can get longer bolts at the hardware store and use washers to space the sprocket out till you get good chain alignment. If that doesn't make sense tell me and I'll take a picture of one of my bikes so you can see what I mean.
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125cc lifan build 79cc predator series
There's no replacement for displacement. Bigger is better, and too much is never enough.
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  #3  
Old 12-09-2016, 01:26 PM
bigwave bigwave is offline
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Join Date: Dec 2016
Location: South Central Illinois
Posts: 12
Default Re: First build

Kind of what I figured, thanks for the replay. Are you saying do not use the cheapo sandwich method that came with the kit? I'm having a bit of a hard time getting it to my satisfaction, I have flipped the sprocket around both ways and still not just right. One way it looks like the chain might hit the outer nubs on the tire and the other way it looks a little out of alignment from front driver sprocket to rear driven sprocket. I'll do a little search, what part are you saying to get, an upgraded sprocket hub of some type?
Thanks
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  #4  
Old 12-09-2016, 01:29 PM
TheNecromancer13 TheNecromancer13 is offline
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Default Re: First build

Yes, I'm saying don't use the one that comes with the kit, it will usually rip your spokes out and is very hard to get proper alignment.

Here are disc adapters: http://custommotoredbicycles.com/spr...rocket_adapter
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125cc lifan build 79cc predator series
There's no replacement for displacement. Bigger is better, and too much is never enough.
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  #5  
Old 12-09-2016, 01:34 PM
bigwave bigwave is offline
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Join Date: Dec 2016
Location: South Central Illinois
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Default Re: First build

Also, where is best place to buy from, and which one do you recommend? Does this allow adjustment on the sprocket? I found a few and looked at them, it looks like you could use some spacers (washers) or ??? With this setup I assume you can just adjust the sprocket in or out by where you place it on rear wheel hub??
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  #6  
Old 12-09-2016, 01:39 PM
bigwave bigwave is offline
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Location: South Central Illinois
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Default Re: First build

I see what you sent, does this have the center split part that goes on the inside of the wheel over the hub? With out seeing how it attaches I'm a bit confused.


Quote:
Originally Posted by TheNecromancer13 View Post
Yes, I'm saying don't use the one that comes with the kit, it will usually rip your spokes out and is very hard to get proper alignment.

I see what you sent, does this have the center split part that goes on the inside of the wheel over the hub? With out seeing how it attaches I'm a bit confused.

Here are disc adapters: http://custommotoredbicycles.com/spr...rocket_adapter
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  #7  
Old 12-09-2016, 01:43 PM
bigwave bigwave is offline
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Join Date: Dec 2016
Location: South Central Illinois
Posts: 12
Default Re: First build

I do not have a disk brake hub. I do not believe this model would work for me, what about one that goes over the center hub of rear wheel, one that is a 2 piece inner? Is there a universal one that would work with my existing sprocket, I don't want to dump a ton of $$$ in this until I know I like and enjoy.
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  #8  
Old 12-09-2016, 08:32 PM
TheNecromancer13 TheNecromancer13 is offline
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Default Re: First build

If you want to use a hub adapter you will need to measure your hub diameter and get one that fits it. You will also need a wheel with 36 spokes. I would recommend getting a better sprocket to go along with the hub adapter. Many adapters will come with a sprocket. Here is an example of the type of thing you want: https://www.amazon.com/Manic-Mechani.../dp/B00LGXTOVG

Again you will need to measure your hub with a set of calipers to get an accurate enough measurement. Some hubs won't work with any of them.

BTW, did you replace any of the parts that came with the kit, or is everything still stock? I ask because there are a few parts that you can replace for a few bucks that will make your ride much less likely to break down.
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125cc lifan build 79cc predator series
There's no replacement for displacement. Bigger is better, and too much is never enough.
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  #9  
Old 12-12-2016, 08:30 AM
bigwave bigwave is offline
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Join Date: Dec 2016
Location: South Central Illinois
Posts: 12
Default Re: First build

First the parts, yes we did put in a "bolt" kit that had harder bolts, studs, etc. What else do you recommend. Please advise and give me a lists would be GREAT. I've fabricated a spring loaded chain tensioner, still work in progress but feeling much better than the "fixed one that came with it".

As for the wheel hub, I may be hosed with this bike, it is conical on the outer edges, it's the same diameter in the center but only for about 30mm (1.2") or so. Yes it is a 36 spoke wheel and appears pretty true and solid. The rag adaptor went right on, I just don't care for that setup, but may give it a try.

The rear wheel hub is kind of like this, but not that much, but you get the idea.
\___/
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  #10  
Old 12-12-2016, 11:03 AM
TheNecromancer13 TheNecromancer13 is offline
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Location: Portland, Oregon
Posts: 556
Default Re: First build

In terms of cheap parts to replace, the fuel line is very low quality. Orchard or home depot have better fuel line. You already replaced all the bolts and studs, that is good, otherwise that would have been the first thing to do, cheap bolts caused me more problems with my first kit than anything else. The spark plug and spark plug boot usually fall apart pretty fast (my spark plug failed on the first test ride). A good replacement spark plug is the NGK B6HS. Any decent carbon core spark plug boot from the auto parts store will do. Chop one end of the boot off and unscrew the old one from the CDI, then screw on the new one in it's place. The fuel filter is made of cheap plastic and will crack easily and spill fuel everywhere. Use an in-line fuel filter meant for a lawnmower or the like. Throw away the fuel petcock, it is useless and doesn't actually do anything. Go to the hardware store with your gas tank and buy a barbed brass nipple to replace it with. You may have to re-tap the hole, as they usually have metric threads. Depending on what kit you ordered and what upgrades you plan to do, you might also consider replacing the chain. The chain quality varies wildly from kit to kit, I had a chain that broke pretty quickly. #420 chain is good. On some bikes it is possible to get rid of the chain tensioner entirely. If this is the case with your bike, you should do it. You may be able to use half links if the chain isn't the right length. On hub adapters, it sounds like your hub won't work, but I can't say for sure unless we get a picture and accurate measurement of the diameter. If you choose to try the rag joint, the wheel should last long enough for you to decide whether you like riding, but it probably won't last more than a hundred miles or so. If you replace the wheel, you can get a rear wheel with double walled rims, 36 triple laced spokes, and a disc hub for about a hundred bucks at performance bicycle. Then for another hundred or so you can get a nice disc adapter and a custom sprocket for 420 chain from rebelgears. I would recommend upgrading the sprocket because the stock one is cheap and I could literally bend mine with my hands, so I don't trust them. If you have a drill press (or if you're really patient and careful, you could probably get away with a handheld drill), you could also make your own disc adapter for a lot less, I can walk you through it if you want to go that route. In terms of more complex (expensive) upgrades, the first one is that your engine will probably 4 stroke from running too rich even at the leanest setting on the carb. To fix this you will need a smaller carb jet. The air filter is also rather ****ty and restrictive, a cone air filter would be a lot better. Also, if you want more power and speed, make yourself a good expansion chamber. A good one can easily double the torque of these engines, as the stock exhaust pipe is a piece of garbage which has the engine way choked down. If you want to see what I mean, try removing the end of the muffler and pulling out all the junk inside, then ride it around the block. It will be loud as ****, but you'll see a noticeable difference in power. Don't ride it this way though, you'll annoy people. A good expansion chamber will provide even more power than just removing the end of the pipe, and it will not be nearly as loud. You can also port the engine with a dremel without too much trouble. Hope this wall of text helps give you some good ideas.
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125cc lifan build 79cc predator series
There's no replacement for displacement. Bigger is better, and too much is never enough.
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