Harbor Freight 99cc friction build

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MaxPower

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Jul 1, 2009
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Sierra Vista AZ
I just placed an order for one. I'm going to have to wait around for a week before I can continue my project :(. Did you have to cut the key down a little to make it fit?

I still haven't got a phone call from AGK. I meet the owner of AGK at one of the death races and he was a really nice guy. I doubt he intentionally miss lead people into thinking that the clutch would fit without modification. It kind of sucks that a $40 ($10 shipping) clutch is now costing $62 (+labor).
 

MaxPower

New Member
Jul 1, 2009
551
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Sierra Vista AZ
I thought I'd share what the project has cost so far. I haven't bought a bike yet and I'm still looking at yard sales and second hand stores. I'm thinking I may just go with a $90 walmart bike untill I find a better one.

HF Engine 90
friction kit 185
clutch 50
sprocket 5
shaft 13
throttle 10
reamer 12
chain 5
rear brake 12
bike 100

total 482
 
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cannonball2

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Oct 28, 2010
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Colonial Coast USA.
FDs are pretty easy on the bike as the tire is catching all the grief, so a cheaper bike should be fine. Just be sure the front fork is pretty beefy as it is the mount point. A rigid front would be best.
 

wayne z

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Dec 5, 2010
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Actualy the Cranbrook is a pretty good bike to start with for the price. Just need to do your own quality control and make sure all the bearings are greased and adjudted.

The wheels are steel with 11 guage spokes, which are sorta loose from the factory. After tightening the spokes and truing the wheels some I find them quite serviceable on my latest 99cc build.
 

MaxPower

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Jul 1, 2009
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Sierra Vista AZ
This is what AGK suggested I do.

We did it garage mechanic style. We mounted the engine in our bike (without
the clutch). We started the engine and let it idle. Then we took a strip
of emory cloth the same width as the output shaft and pulled it over the
output shaft in a shoe shine buffing motion. The shaft was about .001"
larger than the clutch bore. We would shut the engine down and test fit the
clutch. We did this back and forth a few times until the clutch fit. It
didn't take too long and the clutch slides on and off very nicely now.
Thanks
 

MaxPower

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Jul 1, 2009
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Sierra Vista AZ
AGK also said this:

We will be adding an article to the site soon which explains the clutch fitment and so many other details. We hope to have that article posted very soon! Thanks
 

MaxPower

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Jul 1, 2009
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Sierra Vista AZ
I finished the bike but of course there are problems.

I did not ream the sprocket out square and there is a lot of run out. It's not so much that it doesn't work but it's too much for my liking. I'm going to have to do it again.

I revved the engine on accident and the roller cut a huge gash in my tire. This motor has a crazy amount of torque. I'm going to have to get a new tire.

The muffler is very loud being up in front of the rider. It's very annoying

The bike will not say up on the center stand on it's own and i have to either lean it against something or carry a stick around the prop up the engine. I can't think of a way to overcome this and I may have to put the engine in the rear.

On the good side the bike is pretty quick and doesn't have too much vibration. Lots of torque to take me from a stop.
 

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cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Looks great MP! If you like the way the bike works/rides just tweek it. I had to build a stand for mine(check the link earlier in this thread), it wasnt difficult and it worked great. The muffler can be tamed with probably a simple turn down pipe. It will require a good deal of down load on the tire to make the smaller roller grip. I find the best grip around 30psi. You have a ton of power to pull lower pressures unlike a smaller engine. Ride it some, if you like it, refine it until its where you want it. Most of my bikes are in a constant state of refinement, and eventually wind up to be very nice rides.
 

wayne z

Active Member
Dec 5, 2010
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I finished the bike but of course there are problems.

I did not ream the sprocket out square and there is a lot of run out. It's not so much that it doesn't work but it's too much for my liking. I'm going to have to do it again.

I revved the engine on accident and the roller cut a huge gash in my tire. This motor has a crazy amount of torque. I'm going to have to get a new tire.

The muffler is very loud being up in front of the rider. It's very annoying

The bike will not say up on the center stand on it's own and i have to either lean it against something or carry a stick around the prop up the engine. I can't think of a way to overcome this and I may have to put the engine in the rear.

On the good side the bike is pretty quick and doesn't have too much vibration. Lots of torque to take me from a stop.

I used a axle mounted kickstand on my Hongdu fronr mount. It works great along with the regular frame mount kickstand. Might work with a centerstand too.
 

wayne z

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Dec 5, 2010
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If you would change to a much larger roller, you will be very suprised how much better the traction is, and how much less the rolling resistance is.

The only reason most FD rollers are small is because they normaly have to run at crankshaft speed and they need small dia. to get the ratio right.
With the jackshaft, you can run a large roller and change sprocket to get good ratio.

I used a 3.5" roller on my in-frame preddy FD, and it WAY out performs the smallish rollers that all other FD's I'm famillar with.
DSC_1541.JPG
 

MaxPower

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Jul 1, 2009
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Sierra Vista AZ
If you would change to a much larger roller, you will be very suprised how much better the traction is, and how much less the rolling resistance is.

The only reason most FD rollers are small is because they normaly have to run at crankshaft speed and they need small dia. to get the ratio right.
With the jackshaft, you can run a large roller and change sprocket to get good ratio.

I used a 3.5" roller on my in-frame preddy FD, and it WAY out performs the smallish rollers that all other FD's I'm famillar with.
View attachment 45746
That's awesome. where did you get that roller. I'm currrently using a 1.5" roller and the ratio could be a little higher
 

wayne z

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Dec 5, 2010
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Hey Max, I fabbed this roller myself from a steel pully and a short piece of 3 1/2" pipe. I am lucky enough to have a small machine shop in my basement.
 

wayne z

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Dec 5, 2010
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Man, That turned out great! I am impressed with how clean and uncluttered it is..That motor don't look too big or out of place on there.

I use an axle mounted kickstand on the
front wheel on my solex clone bike. It, along with the regular sidestand, it is very stable when parked.
Doncha love the way these lil motors run?


For future mods,you could improve noise ,efficency and maintenance a lot by switching to a much larger roller(21/2-3 1/2") and driven sprocket.
 

MaxPower

New Member
Jul 1, 2009
551
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Sierra Vista AZ
Way Cool! How does it ride? And only 49cc too(hehe).
It rides very well. I thought there was going to be much more vibration than there is. I think I'm going to make a custom exhaust for it to quite it down a little. I kind of wish it was geared a little higher but this ratio will pull me from a stop. I really like wayne z's vari speed tranny and considering retrofitting mine. Night riding is great with the two 55 watt headlights I'm using. Braking power could be better. I wanted to put the caliper brake on the front but it would not fit with the kit. I know it's just a matter to time until the walmart bike blows up.
 

cannonball2

Well-Known Member
Oct 28, 2010
3,682
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Colonial Coast USA.
Do like Wayne suggested with a bigger roller. I dont know how much clearance you have in the channel but if you can squeeze a 2" in the top speed will be around 30mph and it will pull from a stop. Will be queiter too. My Schwinn bobber with the Preadator runs a 2.6" roller via a belt at a 1:1 ratio, has a top speed around 40 and pulls easily from a stop. If you can use a 5/8 shaft with what you have now, making the roller would be no problem.
 

wayne z

Active Member
Dec 5, 2010
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It rides very well. I thought there was going to be much more vibration than there is. I think I'm going to make a custom exhaust for it to quite it down a little. I kind of wish it was geared a little higher but this ratio will pull me from a stop. I really like wayne z's vari speed tranny and considering retrofitting mine. Night riding is great with the two 55 watt headlights I'm using. Braking power could be better. I wanted to put the caliper brake on the front but it would not fit with the kit. I know it's just a matter to time until the walmart bike blows up.

Can you bolt on a caliper to the back of the steer tube for rim brakes?