mangosmoothie

Mango's mad project

Recommended Posts

started as this, an unloved bicycle with a cheap ebay engine kit. School wouldn't let me park my motorcycle in the garage without a parking pass. So I carefully read the student handbook and basically a motorized bicycle is allowed because it isn't classified as a motorized vehicle per MoDOT definitions. Why not pedal? Because I have to wear professional dress and getting hot/sweaty and grease marks all over my pants from chainrings isn't ideal. So I made this.

 

EORbO4B.jpg

 

It's fun to ride around the neighborhood and commute to school on. Easy enough to do, goes ~30 mph flat out. Cruises low 20's. 

I was having fun and acquired a rolling frame with built in tank. See all you having fun on groms and wanted to make something a little more sporty than what I had. Some guy and Florida had hundreds of these roller frames and was blowing them out before Irma hit. He thought his warehouse was going to be washed away. Also got a cheap mildly souped up chinese engine. I dunno how much these engines make. They say ~5 hp, but I don't know if I believe that.. And to go any faster than 30, I have to gear it to the point I pedal to 15 mph or so before I engage the engine. There's no transmission, just a clutch disc and whatever gear ratio you set with sprockets. And I was having way too many issues with the second chinese motor. 

 

EegsRCg.jpg

 


Then an idea @crash put into my head started taking over. After browsing craigslist for cheap small dirt bikes, I lowballed on a KX60 and the dude let me have it. 60cc (obviously de-stroked to 50cc for legal purposes to ride it on the road ;) ) 2 stroke, 6 speed. This motor makes 14 horse according to google. The transmission is nice because now I can gear it to do 40's (or more) and still be able to take off from a stop. There's a whole motorized bike community that races and all kinds of stuff for this. It's actually a huge thing in St. Louis. People spend $800 on 10 horse engines, and another 250 on kits that allow you to use a bike's derailleur. The entire KX60 dirtbike was a fraction of that. And there isn't really a rule book for the series soooooooo......... :)  

And for fun

 

Ninja 250 with a rider -   ~475 lbs and 30 hp

Grom with a rider - ~400 lbs and 10 hp

Mango's bike with mango on it -  ~ 200 lbs and 15 hp. 

 

So...... should be pretty quick :) 

The motor fits in the frame fine. @ZRX4ME helped me cut some brackets among other things with this project. The hiccup now is getting the exhaust to fit. Might have to go to a muffler shop. Or the other idea I had was just use a small section of exhaust flexible tubing between the outlet and expansion chamber just to get the pipe routed around the frame. and I gotta get the pedal cranks to clear the right side engine case. 

 

QpKl0iK.jpg

 

 

Sm7o3bD.jpg

 

 

  • Like 3
  • Upvote 1

Share this post


Link to post
Share on other sites

Holy moly! Nice! :) Destroked to 50cc... right. :)

Share this post


Link to post
Share on other sites

'Obviously destroked'

Share this post


Link to post
Share on other sites

Pro tip. Don't get your pant leg or shoe strings wrapped up in the chain! :)

Share this post


Link to post
Share on other sites

I need to make the exhaust fit. Flex tube is the easiest answer. Just cut out the stock u bend and use flex tube to make a new U bend. 

Could also cut the kx flange off the stock pipe and have it welded to the pipe made for that frame. But the expansion chamber for the pipe for that frame is smaller than the kx expansion. 

Share this post


Link to post
Share on other sites

A properly tuned pipe and that 60 will be hard to hang onto! I would go with an FMF Gnarly or a Pro Circuit. :)

Share this post


Link to post
Share on other sites
9 hours ago, mangosmoothie said:

 

Ninja 250 with a rider -   ~475 lbs and 30 hp

Grom with a rider - ~400 lbs and 10 hp

Mango's bike with mango on it -  ~ 200 lbs and 15 hp. 

Tire size, as in height, of your project might have a negative impact on your comparison there.  But, good luck!

Share this post


Link to post
Share on other sites

Very nice.  I cant wait to see how it comes along.

Share this post


Link to post
Share on other sites

According to the motorized bike community I'm going to 

 

1. Break the frame because too much power (don't think I will. This engine isn't torquier than the chinese motors. Probably less torquey. Just more hp because it revs higher)

2. Break the pedestal engine mount (possible I guess)

3. Rip my spokes out of the wheel (the keen observer will note I have no spokes)

4. Need a one off rear sprocket to accommodate a 420 chain (420 chain fits fine around the 415 sprockets I have. Spacing is the same. 420 just a tad wider. So no issues there)

 

According to the dirt bike community I need to

 

1. Cut the downtube of my bike frame and fabricate another to accommodate the stock kx60 exhaust pipe (not going to happen)

2. Use the bottom half of the kx frame (not going to happen)

3. Move the engine down because it's too top heavy (it's not)

4. make supports to hold the engine since it's super heavy (it's not. Weighs almost the same as the chinese motors)

  • Upvote 1

Share this post


Link to post
Share on other sites

Sounds like you're blazing new territory so it's just a case of engineering the best you can, try it out, if something doesn't work, mod it until it works, or maybe in the end you figure out it's not the best solution. But, maybe it will be a kick ass solution! :)

Share this post


Link to post
Share on other sites

P.S. How do you plan to start the engine? I assume kick starter will not work or be in a convenient location, or is it not an issue?

Share this post


Link to post
Share on other sites

Yeah, it is uncharted territory. I hope I don't break the frame. 

From an engineering standpoint, I think torque is what would break items. 8 ft lbs doesn't seem like much. Humans peddling make more tq than that. Hp is torque over time and this engine just revs to 12k rpm instead of 8k rpms like the chinese engines. And the rear wheel shouldn't be spinning any faster........ because I don't plan on going for a top speed much over 40.... 

Guess the "easy" way to figure it out is to just gear up and ride it when I get it all mounted.

I plan to start it with the kick starter. It's not in the way of anything. I can put left foot on ground and still reach the kick with my right foot. If I can get the crank on the right side to clear the engine case, I could also try bump starting it in a higher gear while peddling. 

 

and for now, going to make a U pipe to the expansion chamber with flex pipe, exhaust tape, and putty. Lol. Just to see proof of concept. Then I'll see about having a real pipe welded. 

Share this post


Link to post
Share on other sites

So are you going to rig up a clutch lever and shifter?

Share this post


Link to post
Share on other sites

yeah. the clutch lever is already in place. the Chinese motors used a clutch like a motorcycle too, just direct drive with no trans. So neutral on the chinese motor powered bike was just pulling the clutch lever which disengaged the engine so you can pedal (and there's a little button that keeps the lever in so you don't have to hold it constantly).

 

Should be able to move the shift lever out of the way of the pedal.

Share this post


Link to post
Share on other sites

But it would be cool to have a shifter bike. :)

Share this post


Link to post
Share on other sites

test ride was a success. This thing is pretty stupid fast for what it is. I was running an open exhaust, not an expansion chamber like I should be, so it'll be a lot faster with a proper exhaust. Banging through 6 gears is pretty fun :)

 

Rigged this up last night. Might be better than open dump, but still not idea. 6-8" of header tube before the expansion chamber is more ideal. I'll work on a better solution later.

 

22219722_10209200262193017_6734164154455

 

The clutch is sticking, it won't disengage completely. I knew about this but ignored it. Now that the bike runs, time to fix it. Hopefully just sticking plates. A new aftermarket clutch with friction plates, discs, springs, and gasket is $30 so I'll go that route if needed.

  • Like 1
  • Upvote 1

Share this post


Link to post
Share on other sites

got a stock exhaust to fit. Took it for a rip and OH MY GOD. This is stuuuuuuuuupid fast. Once it comes on the pipe it's hard to hold on. These 2 strokes pull HARD
 

  • Haha 1

Share this post


Link to post
Share on other sites

Are you going to be drifting it? :)

If you need to weld a pipe, buy the parts and we can get it done. 

Share this post


Link to post
Share on other sites
14 hours ago, Speed said:

Are you going to be drifting it? :)

If you need to weld a pipe, buy the parts and we can get it done. 

 

can you weld aluminum? 

Share this post


Link to post
Share on other sites

We know he can make aluminum shavings.

Share this post


Link to post
Share on other sites
38 minutes ago, mangosmoothie said:

 

can you weld aluminum? 

I will be when I pick up the TIG welder that I won in the auction... I would need to practice first though.

28 minutes ago, crash said:

We know he can make aluminum shavings.

Yes, JJ admires the shavings every time he goes in that garage :)

  • Upvote 1

Share this post


Link to post
Share on other sites

Found where he stole the idea from (Moto Europa museum)

 

 

20171006_130638_Film4.jpg

  • Like 1
  • Upvote 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now