Need ideas to convert my Harley electric to gas

AGrayson84

Hey everyone I picked up a '79-'81 model Harley Davidson four-wheel electric cart the other day, with intent to fabricate a gas motor in it. The current electric motor is angle perpendicular to the axles, so this is going make the project a little more difficulat if I plan on using the current differential. Here are some pics of what I have to work with:










I decided that I want an electric-start motor with a reverse gear, and came across this type setup:


This is a 150cc 4stroke, 8.72 hp motor. I plan on putting slightly larger tires on the cart and want to make it a toy for the woods. Definitely want it to have a little more low-end power/torque than a stock cart motor, but also would like a few more MPH on the top end. I'm not sure if this motor will give that, and if the smaller CVT transmission will even hold up the weight and driveline of the cart.

What do you guys think? Will I want a bigger engine and/or CVT system? If this won't be the best idea for my use, can you guys give some ideas on how I can fabricate something to this current differential?

BGW

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AGrayson84

By the way, if the above motor would work, I would flip the axle so that the pumpkin was on the driver's side of the cart, then face the output shaft of the transmission toward the output shaft of the differential, and have a small driveshaft placed in-between to connect it all up, if that would be possible.

I definitely don't want to try to put a big driven CVT unit directly on this differential because it could easily get damaged if a rode over something... not to mention it would get wet really easily when going through mud and such.

I also realize that I'll likely have to re-fabricate the rear so that the center frame support can be cut out to make more room for an engine, or I might have to do a whole different rear all-together... but I'd rather just cut out the center frame and support the current rear with a revised structure.

kab69440

If you are dead set on using that body, by far the easiest and cheapest way to get it done is to buy a running gas cart and drop the body over it. The conversion from one drive to another is going to be a huge expense and waste of time. For the life of me, I cannot grasp why so many people buy any given cart and then spend five times its resale value to conert it from one drive system to another. I love a good project as much as the next guy, but the logic of the drivetrain coversions escapes me completely.

You can probably pick up a running 2 stroke Marathon for $500. You'd then have your Harley body and gas driveline to start with. Way cheaper than trying to scavenge all the most expensive pieces one at a time.

People that build those hotrod style carts love the perpendicular motor/axle setup you have now. Selling that will probably pay for most of a donor gas cart. Good luck with your build, and keep us posted, whatever you do. I hope I don't come off as mean or condescending, I really am trying to be helpful.

And yeah, something will need to be done with the chassis, that huge pipe is going to be a pain in the rear...

AGrayson84

Hey kab... no, your advice is very much respected. I didn't know anything about the drive system on golf carts when I picked this thing up... I got it for $25 and just assumed all rear axles were very similar. It was until after I picked it up, examined the situation, then looked at the drive systems on gas carts that I started to realize what I got myself into. For $500, you may be right about being better-off with a Marathon. I'll have to read up on Marathons... I've seen the name tossed around but have no idea what they are.

Any idea what the hotrod style cart builders are running for engine and/or trans? Or what they are using to connect the power to this type of differential? If a small driveshaft is all that they use then this may not be as horrible as it sounds. I just have to put a motor in it side-ways instead of facing front-to-rear. Any input you can provide on how that can be accomplished would be awesome.

I know I must sound like just another guy who thinks he's going to be able to pick up a welder and do it all himself, but I do plan on picking up a welder and trying to do most of it myself :) I'm very mechanically-inclined and love working with metal, just never have had my hands on a welder to do things that I want. My friend used to weld up baja cars from scratch so I'll be able to get a huge hand from her. I don't think cutting out the center tube support and re-bracing the rear will be much of a task, so it's just fabricating a motor into place once I figure out how I'm going to connect the differential up.

Thanks again for your input... practicality will play a huge role in this.

kab69440

When I say "hot rod" cart, I am referring to carts with old roadster bodies on them. The motor in front of the axle is needed because the typical motor over axle is too tall. I can't say I have ever seen anyone attempt to put a gas engine on one of these axles. Might be a huge waste of time as the differential ratio is usually on the order of 12.4/1. If you're running a 3,000rpm motor, do the math. If you also have to add a further reducer to adapt the engine (chain sprockets, belt pulleys or whatever) you could end up with $3,000 in a cart that has a top speed of 4mph. And that just ain't right, hahaha!

I seriously would advise a donor cart for chassis/ running gear purposes. Running an old Harley body on something you can get parts for would be about the best of both worlds. Oh, and a Marathon is an old EZGO cart. They are as rare as belly buttons, and they don't seem to have a large following(I can't figure why? I dig them!) that's why you can usually get a deal on one.

carolinasled

First thing I would do it strip down all the electronics that your not gonna use to determine which way the axle spins in forward motion(just determines which way you need to mount your motor). When You remove the motor, Will there be a male shaft exiting the axle? If so weld on a hub that fits the shaft and then weld on a sprocket to the hub. the shaft exiting my 93 ezgo was 21mm in diameter, I bought this 13/16 hub from surpluscenter.com and had to manually force it on with the help of a hammer. The splined shaft seated in the hub and made new grooves.

http://www.surpluscenter.com/item.as...ame=powerTrans

If it turns the opposite way of the easiest way to mount the motor, You could run a jackshaft to make it work.

I'm using a small block 6.5hp honda clone engine with a tav2 torq converter. my stock axle is 12.44:1 with a top speed of 15mph. I just ordered a new sprockets for my axle and tav2, I'm hoping to be around the upper 20s. I have about $425 in my build so far.

Looks like a fun project tho

AGrayson84

Thanks for all of the very helpful info guys! Sorry about the delay in response on my end-- t'was a busy weekend!

Carolina... the TAV2 is 30 series, I'm really surprised/glad to hear that it works on something this heavy. You haven't been wearing that belt down pretty quickly? I would expect that trying to get something this heavy going would wear out such a small belt pretty quickly. Think I might be better off going with a 40 series or something if I were to try to make this axle work?

The only thing that I'm afraid of is putting much of a sprocket on the differential spline... if it is hanging down low at all, all it will take is for me to run over a log, rock, etc. and bend up the sprocket or break it, or the shaft that it rides on. Anything smaller in diameter, then I might end up with almost no torque.

Carolina, you cart sounds like a pretty reasonable setup. Any pics of your drivetrain/driveline???

AGrayson84

This might be a stupid question, but I saw on some of the gas carts that the driven clutch is attached directly to the differential. I wouldn't want my driven clutch that low to the ground because of my different axle and differential location... but if I were to use a jackshaft with a small sprocket, the same size as one that I would directly slap on the diff, if that gave me a 1:1 ratio that would be the same thing gearing-wise as if I were to attach the driven directly to the diff, right??

carolinasled

Not been wearing that much at all. The throttle did lock up on wide open during a trial and error testing and started to wear but is fine. There is a pic in my build of the drive train. I just installed a custom 23t sprocket to the tav2 and there is fresh pics in the build thread. Since the axle is 12.44:1 I installed a little sprocket on the axle and bigger one on the tav2 and it has put it in the upper 20s.

AGrayson84

Saw the new videos you posted... your progress is very inspiring! So with that 23t up front, you have more than enough top speed for me at around the upper 20 MPH range. How does the cart feel at low RPM? Think you'd be able to get up a bit of a hill off-road? Or do you think that would require a little more gearing down low?

The reason I ask is because I have a 6.5 hp, running Subaru Robin engine that fires up on the first pull. I probably won't be able to have the electric start that I would prefer, but I can get a Comet gearbox w/reverse and make that work somehow.

Another option is an air-cooled 500cc twin-cylinder, two-stroke snowmobile engine that I have. That engine runs great too and has a much larger CVT system on it... I'm just not sure how good of an idea it is to use an air-cooled snowmobile engine. I suppose I can always install an electric fan or two, to blow against it, but I've heard someone mention before that those engines should not be run anything below freezing temperatures or you can melt the pistons. Not sure how true that is...