80cc Motorized Bicycle Engine

[Timmahhhhh]

Has anyone used a motorized bicycle 2-stroke 80cc engine on a mini bike? I have one just sitting around my garage and can't seem to control my curiosity. Mine came from KingsMotorBikes. How many hp do these things make? They are rather persnickety things to keep running-is there a secret to reliable operation?

 

[TOTAL CARNAGE]

WOW!!! Something I can help with. I may be new to mini bikes but I've been building bikes for years. Between my wife and I we have 8. All but one are gas and of them all but one are antiques. oldest two are 1940's and the newest is a 58'.
While I like the "motorcycle" look of the happy time motors and they work great on a bike I would not recommend them for a mini. They claim 2hp but ?? maybe.....maxed out. I have 2 with over 1000 miles on them. The only secret I have is build it right to begin with and then don't hammer the heck out of it. The little China engines just won't last if you ride them wide open, they won't take the high rpm's. We just putt ours around town with a normal speed between 12 and 15mph and I have no doubt they will be around a long time.
On a mini, with little wheels it would be screaming and only going about 10mph.....jack shaft.....cvt......gears.....to much work and all that gearing would eat up all the hp.
Use it to build a nice bike and put your time and money into a H.F. engine for the mini. :thumbsup:

 

[SimpleTom]

Now this one is cool!!

 

[trailbronc]

that is AMAZING... :scared:

 

[TOTAL CARNAGE]

Thank's guys!
Funny, That is the only one that's NOT an antique! That was built from a $89 Wal-mart Cranbrook :laugh:
this is the way it looked when I got it.

 

[Oldsalt]

Total Carnage

That yellow Wal-Mart bike is beautiful! I have an old Murray 3 spd, 26" bike with a 66cc motor but it is an ugly duckling in comparison to that machine! Can't wait to see what you build for a minibike! Tell us about the Salt Flat wheel covers...Bet I'm not the only one that is wondering how you did that.

 

[TOTAL CARNAGE]

Great call Oldsalt! That is exactly what I was going for, an early salt flat racer. From the moment I saw it in my mind it had disk wheels.
My first try was plastic wheel covers they sell but they looked like....well, plastic. Real spun aluminum disks made by Moon....$300!!! I tried many things from trash can lids to pizza pans and could not make anything work. Couldn't get the cone shape to fit the spokes. Tried using a press but always wrinkled the aluminum. I ended up using aluminum sheet used on the roof of trailer truck boxes. I had to put a seam in it to cup it but it turned out well. A nice bead of Goop glue around the rim is all it took to attach them. That Goop is amazing stuff!!! I hope I never have to get to the spokes, I don't think the disks will come off without damage!
Thanks again. Always happy when people like the "toys" i build.

 

[Oldsalt]

Great call Oldsalt! That is exactly what I was going for, an early salt flat racer. From the moment I saw it in my mind it had disk wheels.
My first try was plastic wheel covers they sell but they looked like....well, plastic. Real spun aluminum disks made by Moon....$300!!! I tried many things from trash can lids to pizza pans and could not make anything work. Couldn't get the cone shape to fit the spokes. Tried using a press but always wrinkled the aluminum. I ended up using aluminum sheet used on the roof of trailer truck boxes. I had to put a seam in it to cup it but it turned out well. A nice bead of Goop glue around the rim is all it took to attach them. That Goop is amazing stuff!!! I hope I never have to get to the spokes, I don't think the disks will come off without damage!
Thanks again. Always happy when people like the "toys" i build.

Did you know that the really early [50s or so] wheel covers used on salt cars were the aluminum lids off old wringer type washing machines? Good tip about the Goop. The pic is of my ugly ducking 66cc Murray. Very dirty...it has been ran hard and put away wet repeatedly. Never have had any problem with the China engine. But you might be able to see the 'tin' clips, provided in the kit that are suppose to clamp the engine and tank in place, have been replaced with shaped aluminum blocks. The next one I build, and there will be a next one, will have fat tires. 20 mph on them skinny 26inchers can become tedious because I have to be vigilant about potholes.

Would a motorized Tandem bike be allowed to posses two engines and still be in the 'Moped' class? I intend to find out the hard way.

I know there are folks on this forum that are wondering what minibike type item your talents will produce.

 

[bigrob]

Oh man I need to keep my eyes open for one of these engines , as for if one would work on a minibike , if the frame was small and light like say a replica of an early GoKart Cycle or a similar vintage frame then it certainly would look cool.
Rob

I was looking thru the photo gallery and think one of those bike engines would look cool in a Keystone replica build.
Could even use the tank under the frame tubes to help with the illusion

 

[Timmahhhhh]

I was thinking of a Lil'Indian or something little like that. I have a Bird Sprite,but that's getting a 99cc Predator when I finish it. I figure the 80cc 2 stroke bike could go 20 mph on flat ground with the proper gearing-which would be good enough for me. I agree with the person who said that the Chinese motors don't like full throttle all the time-they start to "four stroke" very easily. Vibration is also an issue. But you have to admit,they do look retro cool.

 

[Timmahhhhh]

This is my motorized bicycle-called "Buzz Bomb #5". It consists of a 26"Schwinn cruiser frame,MTB forks,and 20" wheels. I tried to give it an old-fashioned flat track look (similar to a Bultaco Astro). I put a SickBikeParts expansion chamber on it and a carb from a pocket bike. She goes real good!!!

 

[TOTAL CARNAGE]

The Murry looks good for a rider. Cables and wires tied up, speedo, lights.
Nice...I have seen some real..well, not so nice builds. All my bikes are on Fat Tires. Like big tires :thumbsup: Still, like Timmahhhhh said, 20mph is good enough for me. That's plenty fast on a bicycle.
About washing machine lids :doah: I didn't know they used them but in my search for disks one of the things I found was a washing machine lid.....just one. Now, just down the road is a guy I ran buggies with years ago but haven't talked to in a while. I noticed he had some old washers sitting behind his shop so I stopped in to see if he had any lids. Turns out he is into restoring old Maytag engines. Rather than just mounting them on fancy engine stands, He also restores the machine to mount them in!! Offered me $40 for the lid I had! So I just gave him my lid and continued the search :laugh:
Here is my first mini bike. 1970 Roper Big Wheel.

That's as far as it gets before I can afford the clutch, throttle, brakes.........Guess where I got the tank?
This is the next

This was going to be a HIGH power electric bike but is now going to be a mini that will push the limits of the law for Pa. In Pa. Under 50cc(the so-called 80's are really 66cc and what I run anyways), less than 25mph and the pedals still work it is a motor assisted bicycle. It's allowed anywhere a bike is "bike lanes, ect" and needs no registration, license or insurance.
Anything over and it's a moped and needs plates and insurance. Now this one will be a bit over at 97cc but I'll ride slow.....Honest! I'm working on the pedals now. Normaly they will be locked back and down for foot pegs but by pulling a pin, one will rotate 180deg. and work like a bike. I'll see how long I get away with it!

I'm also thinking of the third....never have to many projects!! If I can just figure out how to stuff this gx390 into the other Roper.

Maybe a jr.daragster slick in back, StageIII engine kit .....:devil2:

 

[Timmahhhhh]

I'm thinkin' maybe someday I'll stuff a Predator in the Schwinn frame.......Brakes are the weak point. I'll keep y'all posted.

 

[Oldsalt]

I'm thinkin' maybe someday I'll stuff a Predator in the Schwinn frame.......Brakes are the weak point. I'll keep y'all posted.

A 'lawn mower' type motor that we use in minibikes will generally produce too much torque for the spokes in the rear tire. That is generally the case but a guy could maybe get by with a really good strong laced rear wheel and didn't jump the throttle to hard.

 

[Neck]

Something on the salt, a bit larger than 80cc's though.

There's another one just like this one (all the guys you can see are standing around it) behind it in the impound area that had just ran a record run of 69 MPH! One of those guys is Shane from AGK.

 

[Oldsalt]

I was thinking of a Lil'Indian or something little like that. I have a Bird Sprite,but that's getting a 99cc Predator when I finish it. I figure the 80cc 2 stroke bike could go 20 mph on flat ground with the proper gearing-which would be good enough for me. I agree with the person who said that the Chinese motors don't like full throttle all the time-they start to "four stroke" very easily. Vibration is also an issue. But you have to admit,they do look retro cool.

The 4-stroking at full throttle means it is running rich. The easiest way to lean the China bike motor out, a little bit, is to gut out a lot of the baffles in the muffler. The exhaust will then tend to 'over scavage' which will make it run leaner. The noise does not increase much.

I believe they jet them super rich so that they are a lot harder, or impossible, to seize-up due to running lean which would cause them warranty problems. To get smaller jets might be possible but I could not find any. The other road is to solder up the hole in the jet and drill it out with a slightly smaller drill. But the drill sizes needed are close to #80 which is a special set of number drills. A standard set has a smallest of #60 which is way too large.

My Murray will run a true 22 MPH on level blacktop...if I put my nose on the handlebar clamp!. Yes! 20 is fast enough. If I leaned her out a little more, so that there is absolutely no 4-stroking at full throttle she'd go a lot faster....but would probably dramatically shorten it's life.

 

[Oldsalt]

Neck

Beautiful bikes! You sure them aren't 50cc machines?

 

[Neck]

The 2 stroke may be a 50, the 4 stroke is a 99cc predator motor I believe.

 

[Salvage Bikes]

Howdy from member of Motorbicycling.com

I found the picture of the 20" wheel beach cruiser on Google, and liked the thread, so I joined. ThatsDax has upgrade carbs for the china-kits, and jets and so on for the stock NT carbs they often come with. (They usually come with a CNS adjustable carb, or an NT barrel slide carb with a screw-in jet and a notched needle for adjustment).

There is a lot of advice on these engines and a section of the forum called "wild in the streets" for home-builts and mower/tiller engine conversions.

Here is a Bultaco Astro photograph, since you mentioned this bike in your thread topic post. http://www.midamericaauctions.com/wp-content/uploads/2011/11/bultaco-astro-4-1-2350.jpg

The 4-stroking at full throttle means it is running rich. The easiest way to lean the China bike motor out, a little bit, is to gut out a lot of the baffles in the muffler. The exhaust will then tend to 'over scavage' which will make it run leaner. The noise does not increase much.

I believe they jet them super rich so that they are a lot harder, or impossible, to seize-up due to running lean which would cause them warranty problems. To get smaller jets might be possible but I could not find any. The other road is to solder up the hole in the jet and drill it out with a slightly smaller drill. But the drill sizes needed are close to #80 which is a special set of number drills. A standard set has a smallest of #60 which is way too large.

My Murray will run a true 22 MPH on level blacktop...if I put my nose on the handlebar clamp!. Yes! 20 is fast enough. If I leaned her out a little more, so that there is absolutely no 4-stroking at full throttle she'd go a lot faster....but would probably dramatically shorten it's life.