80 MPH mobility scooter: Sold

[the german]

I have had an itch for this ridiculous (...ly unsafe?) project ever since I first saw this video:

[youtube]https://www.youtube.com/watch?v=zy5rkw4SeP4[/youtube]

Haha!! Completely nuts!! That one has a CR125 (~25 HP) motor and tops out at just over 80 MPH. I of course have to go bigger, so I plan to use a two-stroke 250 (~40 HP).

I have had my eye out watching for a cheap four wheel scooter to pop up on CL for almost a year, and it finally happened about 3 weeks ago. Behold- a $120, functional mobility scooter, in super classy gold spray paint:



The goal is to make this thing awesome, while spending as little money as reasonable/possible. As a result, all the raw materials used to make new parts have been scrounged from the scrap bin at my work. All other parts will be found on CL or bought for super cheap ($1-$16 shipped) on Ebay.

First order of business: solid rear axle conversion. Made a solid rear axle from some 1 1/8" round bar (free from scrap bin). Took the opportunity to widen the rear track by 2".



A little bit of poke...



Welded extensions onto the rear frame w/ scrap 1" square tube (it's made to come appart so you can fit it in the trunk of a car!)



Milled slots in the frame rails to allow for chain tension adjustment, and mounted up the rear axle using some self-aligning pillow block bearings:

[Dutchbroracer]

Haha badass. Love projects like this.

[the german]

Looking into brakes, the natural/easy thing to do would be a single rotor/caliper on the rear axle like most every go-kart. This was the route taken by Colin, the guy who inspired this whole thing. But sitting in the garage looking at it, I spotted my old mountain bike hanging on the wall and got a crazy idea: FRONT DISC BRAKES!! YESSS!!

This will allow for power braking = SMOKEY BURNOUT TIME!!

So I robbed the cheap cable disc brake setup off my old bike and started exploring what was needed to make it work.

The concept:



This posed some problems though..

Problem:
no provision for mounting brake disc to wheels

Solution:
Custom aluminum adapter hub

Problem caused by solution:
The spindles were not long enough to accommodate a hub to mount the disk on the back of wheel.

Solution:
longer spindles... duh!

Problem caused by solution:
wheels are now further from the pivot, and hit the frame/body work when turned even slightly

Solution:
completely new front frame, moving the front axle forward 1.75" and improving the steering geometry over the stock scooter (which was designed to drive 5.5 MPH...) and a bit of trimming to the fenders

So just a little bit of scope creep there

scrounged some more 1" square tube and got to work on the frame.

Stock frame... which was quite the flexy flyer, and in no way square!



New frame, which is quite stiff and actually square!







Body work fits pretty nicely:



Next up, brake adaptation parts. I spent yesterday machining these at a friends shop, using his manual mill and lathe.

Disc mounting hubs: these bolt to the back of the wheels using the bolts that also hold the two halves of the wheels together, and locate on the spokes







Came out nice and seems to work quite well



Now to make the longer spindles-





Here is a comparison of old vs. new spindles. Another thing I changed was retaining the wheels with a nut instead of a snap-ring. I'm not about to trust a tiny little snap ring to hold @ speed...

[the german]

Haha badass. Love projects like this.

haha thanks!

[the german]

OK, now it's engine time. I started watching CL for a cheap, water cooled two-stroke in the 125-300 cc range as soon as I bought the scooter. Last weekend I drove three hours and took two ferry rides to pick up small pile of 1984 Suzuki RM 250 parts for $100: frame, swing arm, gas tank, motor (in pieces, in a box), carburetor (w/ no jets.. useless), rear wheel, and radiators. The only thing I cared about was the motor, carb, and radiators.

In looking at the motor, the cylinder and piston looked to be in good shape, so I cleaned them up and bolted the motor together to see how it turned over.

Cylinder wall - looks pretty good:



Motor turned over nice and smooth, built compression like it should. Awesome.

The rear swing-arm bolt was rusted-in to the motor, and had been cut off by the previous owner so he could get it off the frame. I don't need it, so I just lopped it off to shorten up the motor.

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Now to find a carburetor. The stock carb is a 36mm flat slide Mikuni. A few model years later, Suzuki upgraded to a 38mm which reportedly improved throttle response and made 40.6 HP (according to an old dirtbike magazine review I found online). The problem is that everything I was finding on eBay and elsewhere online was ~ $150-$250; well outside the budget for this project.

Well, this last week I found a guy selling a 38 mm flat slide Mikuni for a 1980's KX250... brand-spanking-new, $75. He spent $300 on it for an outlaw go-kart, then decided to swap in a 450 four-stroke. I love Craigslist.

Yesterday evening I threw the carb on the motor, made a kicker pedal to start it with, and threw in a new spark plug and coil. Gave it a few kicks, and guess what?!!? IT RUNS!!! WOOOHOO!!

[youtube]https://www.youtube.com/watch?v=lJjhXujt85Y[/youtube]

[scubagli]

Nuts

[the german]

One last little addition for the day-

With the motor running I swapped on a smaller drive sprocket. The stock one was a 13T, and I found a new 12T on eBay for $9 shipped. Every bit helps. I'm trying to gear this as short as possible to get the most out of the low end and allow for better drifting, so I'm planning to use a 22T sprocket on the axle which is about the biggest I think I can reasonably fit. According to my gearing calculations, this will put me topping out at about 67 MPH in 1st gear.

[elaw]

The fact it's not Audi isn't the problem... it's that it's not quattro.

[the german]

Better for drifting that way ;-)

[lorge1989]

Needs more quattro, this is awesome. You should keep a little table going on total investment so far.

[the german]

Needs more quattro, this is awesome. You should keep a little table going on total investment so far.

Lol I have a spreadsheet cost-tracker going... so far total investment is $503, but that will go down a bit in two days when the eBay auctions selling the stock drive motor and controller end. I will post a copy of it tonight.

[elaw]

The only thing better than a cool project is a cool *cheap* project!

[20VAvant]

Needs more quattro, this is awesome. You should keep a little table going on total investment so far.

Lol I have a spreadsheet cost-tracker going... so far total investment is $503, but that will go down a bit in two days when the eBay auctions selling the stock drive motor and controller end. I will post a copy of it tonight.

So you are saying that this should be an affordable venture and that all of us here will have to arrange a meet and race our 40HP scooters?

[the german]

HAHA! We definitely need to start a scooter drag racing league!

[ringbearer]

Holy crap!

You're not messing around, or wait, maybe you are

[alxdgr8]

This is awesome! I'll definitely need a ride when it's done!

[themagellan]

[the german]

This is awesome! I'll definitely need a ride when it's done!

Lol there have been two reactions I have gotten: that one, and "you're going to die" come on over when it's done and give it a spin!

[the german]

First off, here is a rundown of the total cost for the project so far:

Scooter..........................................$100
Engine, bike parts.............................$100
4 new front wheel bearing.......................$8
keyed, weldable drive hub......................$12
expansion pipe, muffler, spark plug..........$90
Cutting & sanding disks........................$20
carburetor........................................$74
new ignition coil.................................$11
12T sprocket.....................................$13
22T sprocket.....................................$15
520 chain.........................................$17
pod air filter.......................................$5
top-end gasket kit...............................$15
Pier 1 wall basket................................$10 (you will see why later...)
ATV throttle........................................$8

Total.............................................$498



**my wife corrected me, apparently I only spent $100 on the scooter because I told the guy he could keep the batteries

[the german]

Ok, now an update for the night-

Started off with making the tie-rod arms for the spindles:



welded them on:



Then while those were cooling, I worked on some other little things. I sandblasted the exhaust flange at work today, so I decided to make the tube that slips into which the expansion pipe will be welded to. I didn't have tube the right size (again, working from the scrap bin here...) but I did have some stainless that was just a little bit to big..



Fits like a glove!



By that time the spindles were cool so I started looking at brake caliper placement and what I needed to do for mounting brackets. Here is what the placement looks like:

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And finally, the ATV throttle I ordered came in the mail today, so I test-fit it on the handlebars. There will be some trimming of plastic needed to get it inset on the handlebars far enough

[gregdell1121]

I am locked in! I saw the video of the original scooter guy and could not stop laughing at how awesome the idea and execution was. I love it! Great work so far!

[dana]

this is going to be horrifying. I've driven a 250cc shifter cart and I almost lost my mind, and that thing actually hooks up, handles and brakes very well. This thing is going to be the absolutely terrifying in every way.
Awesome.

[the german]

I am locked in! I saw the video of the original scooter guy and could not stop laughing at how awesome the idea and execution was. I love it! Great work so far!

Thanks!

[the german]

this is going to be horrifying. I've driven a 250cc shifter cart and I almost lost my mind, and that thing actually hooks up, handles and brakes very well. This thing is going to be the absolutely terrifying in every way.
Awesome.

hahaha yeah, when thinking of names for the project I keep coming back to "Unsafe at Any Speed". Looks like shifter kart tires would fit on these wheels.......

[dana]

you might be better off with less traction, with such a high center of gravity shifter cart tires might make it flip instead of drift. You probably just need several sets of tires depending on the track event you are running

Oh, and very nice work BTW. I love seeing projects that are TERRIBLE ideas executed so well