carguy123 SuperDork
7/31/10 3:45 p.m.

Seeing all those posts on the F500 and F600 thread made me start thinking about the CVT tranny & diffs needed to run an engine like a snowmobile or motorcycle engine in a car.

Are they readily available at reasonable prices?

I love CVTs for autocross and am attempting to find a way to attach a motorcycle engine that fell into my lap into a bare bones, nothing but a driver and motor autocross fun car. IT'S EXPENSIVE TO ADAPT A BELT DRIVE MOTORCYCLE ENGINE TO ANY TYPE OF DIFFERENTIAL!

MadScientistMatt Dork
7/31/10 3:49 p.m.

If it's a small race car that has no need of reverse, you could just use the motorcycle's transmission, usually a sequential six-speed, run a chain and sprocket to the axle, and not use a differential at all. The motorcycle transmission is usually in the same casting as the engine block on a sport bike motor.

carguy123 SuperDork
7/31/10 3:57 p.m.

I forgot to mention I'm not worried about classifications as this is just for fun. I have plenty of fun venues close to me.

Mad Scientist - No diff? My off road go karts don't have a diff, but their track is pretty narrow. Can you get by with no diff and sticky tires on asphalt and concrete?

And yes, reverse will be my feet. I'm probably going to leave a spot thru the floorboard for footwork. The places I'll be able to run it aren't covered over in rocks or other debris and I'll probably never run it in the rain. If I go off, usually I could loop around and not have to use reverse.

This particular engine has the transmission separate from the engine so a CVT could probably be hooked up. I have the motorcycle tranny but never considered no diff.

grimmelshanks Reader
7/31/10 4:03 p.m.

i know a dude that runs autocrosses all the time in a bluebird with a welded diff and very sticky rubber. particularly if this creation of yours has a fairly narrow track, you could totally do it.

racerfink Reader
7/31/10 4:20 p.m.

Plenty of cars in road racing run a "Lincoln" locker. That is, a welded diff. It never hurt the ITC Toyota Corolla my dad and I ran.

Most safety stewards would probably not let you run with a hole in the floorboard.

carguy123 SuperDork
7/31/10 4:52 p.m.

Boy that certainly simplifies things! I never dreamed you could run a straight axle on concrete. So what size/kind of axle would I need? I've seen many of the off road go kart things with the straight axle and a single disc brake on it, but nothing that I thought would stop a car going 60ish.

I liked the CVT from the standpoint of one less thing to worry about in a run. Just plant it, turn left, turn right and go, go go!

This isn't a high revving jap bike but a 2 cylinder Harley engine, but the price was right, dang near free!

I hadn't thought about the safety stewards, I was just thinking of how to make it work with no reverse.

The car will be as small as I can make it and still fit me, the engine and about 2 gallons of gas. I won't need headlights, tail lights or anything but brakes.

Now I have to figure out wheel uprights and that axle. Oh yea, it needs brakes. The go kart world isn't hauling down that much weight so where's a good place to look for the brakes and uprights? I'm presuming that will lead me to axles.

I was thinking something more car like but as I type this I'm seeing big kart like in my head.

MrJoshua SuperDork
7/31/10 5:00 p.m.

There is a sub $100 adapter that attaches where the motorcycle sprocket usually comes off of the trans. The adapter allows you to turn the bike motor sideways and run a driveshaft. Of course this doesn't help you with your lack of a transmission.

MadScientistMatt Dork
7/31/10 6:44 p.m.

Figured it was a Harley engine when you said it didn't have a transmission. You might just get the separate Harley transmission, remove the belt cogwheel, and replace it with a sprocket. Might need the sprocket machined a little but nothing too fancy.

carguy123 SuperDork
7/31/10 9:42 p.m.

I'm back! Seconds after my last post we got a phone call and our son-in-law was headed into the hospital for an emergency appendectomy. He's due out of surgery any minute now.

There's something about posting. While I was making this post the doctor came out and said his appendix had ruptured, but only very in the last very short time prior to the operation and they think he'll be OK. They have to keep him in the hospital for a day or so due to that. Funny thing is that he wasn't in enough pain for anyone to think he had an inflamed appendix, much less a ruptured one.

As we were waiting for the Doctor I was thinking about the "locker" rear end (does that make be BAD?), wouldn't that make the car push quite a bit? I know the Elise rotates better without a LSD and a locker would seem to cause it to push even more. There's not an overabundance of HP, although quite a bit of torque, to be able to use the throttle to rotate it at will I don't believe.

I do have the transmission, a 6 speed. But because it was a 2 piece affair I thought I might be able to find a way to attach it to a CVT.

Mr. Joshua where can I find info on this sub $100 adapter you mentioned?

The engine is FI so I don't have to worry about floats in a carb if I turn the engine sideways and I'm sure I can rig up some baffles and a change in oil pick up to be able to turn the engine sideways.

I'm going to try to google the F500 cars and see how that CVT attaches and see if I can find out how expensive they are. That really sounds like fun, but sub $100 adapter to allow me to use a Suzuki or other small rear end sounds like it would be more up my pocketbook alley.

MrJoshua SuperDork
7/31/10 10:43 p.m.

In reply to carguy123:

Yeah, I thought you might ask. I used to have it bookmarked-on my old computer! I will dig around a bit and see what I can find.

MrJoshua SuperDork
7/31/10 10:49 p.m.

The BEC (bike engined car) threads mentioned Hawk Machine as a source. Enjoy!

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