JDH: CB750 Conversion - Let the Fun Begin!

With the battery tray that wide, will it be scraping the ground when you go into turns?

Yeah, I'm thinking the same thing John. If it were me I'd think about shortening that seat and maybe puting a box behind it like the scooter folks sometimes do...for a battery back there. Or, I think "saddlebags" and I think why not have a couple of battery boxes made to fit the sides of the rear bolted on and down each side like saddlebags? I know you don't want to get into welding, etc. but since you're spending a fair amount of bucks here anyway...I'd make the battery placement a priority and put my money as well there. Otherwise I'm afraid that you'll end up with something impractical to ride. I'd also look into building or having built some fiberglass boxes...for weight limitation. Also, what about moving that tank and re-positioning the frame bars there so at least one battery can sit in that space perhaps covered by just the top half of the tank enclosure...insulated from the battery of course. Also, what about turning those batts up on end in some cases...as I understand you can do that with sealed batteries? Might save some space. And, there's no rule that says the batteries can't be placed laterally along each side of the frame all the way down to the rear. I know the motor has to go in there somehwere but seems to me that might be workable....figure out how to use the space along the length rather than creating this perhaps unacceptable width. You may also be creating a side to side center of gravity which will be a problem in keeping balance easily.

Not knocking your work here John...just trying to provide some constructive comments!

Gushar

John you've probably already been looking at this and made the decision on total voltage with this consideration...but you know it seems to me that you reach a point with these type batteries because of weight that you loose all or much of the increased power with higher total voltage because of the weight of the batteries to power that size motor/system. Might you rethink that and make sure that you can't go down in voltage...say from your (if I'm correct) 84 volt string to something like 60 volts or max 72? I mean with one or two more batts to get to 84 volts are you gonna get that much more bang in power? I guess it also depends upon what you're looking for in speed, range, etc. I would as well look at some things like the weight of wheels, etc. and see if you might trim off a few pounds there by replacing the stock wheels (not tires) with lighter ones....and anything like that which might lighten the total weight and maybe somewhat lessen the power requirements. I just believe I'd settle for lower speed and less batteries (total voltage)...or perhaps find a really good motor that would give me the best power at a lower total voltage. Anything to lessen the number of batteries. I mean you really are limited by the number of batteries (especially SLA) you can reasonably carry on a frame of that size.

I guess it all depends too on what you're looking for. As for me I'd rather have a practical and reasonable looking machine with less power and a shorter range than a more powerful one, greater range that looks really odd and takes every second of your attention just to keep it balanced as your going down the road.

Gushar

So If I'm getting this right then you plan

4 Batteries in the front section
1 Battery over the motor
2 Batteries as saddlebags

If that is the case then why not have the 4 batteries that are up front in a square? See pic.

This will take care of the width problem and make a nice neat looking package.

Looking good John.

I took my project for a ride last night. (Back and forth in the length of the garage. (We were getting pounded by the snow storm last night.)
Everything is woking well. I was dissapointed, as the motor does not seem to be making any torque. I am hoping to be able to play with the programing tonight and make some improvements. I don't know any of the controller settings sent from the factory, as I have not hooked it to the computer since it arrived.
Hopefully I can change some parameters to increase motor torque.

I'll post some pics soon.

Mike K.

Hey John.
My conversion was pretty simple in comparison. It was amazing how well the Kawasaki 110 4- wheeler accomodated the conversion. The frame was perfect for mounting the batteries and the motor.
FYI I was stressing over finding a sprocket for my motor. A friend of mine told me the #40 chain was compatible with the #428 chain. I was able to order the correct sprocket from McMaster-Carr ready to use for $13.20.
A little research revealed the #50 Chain will work on the #520 chain.

The smallest sprocket I could find in either chain (from McMaster-Carr) was a 9 tooth with limited bore sizes available. As soon as you get to 10 or 11 teeth, the available bore size jumps up to 1" dia shaft. The price was about $12. My stuff was delivered next day regular ground UPS.

I didn't know if you knew that already. But I went from being a couple of weeks to 2 days in solving the sprocket issue.

Mike K.

well I rode the 4 wheeler up the street and back yesterday. It wants to go 30+ MPH. I think the "no torque" problem is a function of the gearing, and small battery pack. I think if I had a large enough AH battery pack, it would go about 45 MPH. The speed just keeps climbing untill the battery pack drains. I tried some changes in the controller programing, but I did not realize much change. My plan now is to add a jack shaft to change the gearing. A quick list of parts required to add the jack shaft is about $110. I am also going to experiment with bigger AH batteries. I have the room, I just need to see if I can find some at a reasonable price. The jack shaft will provide many options as far as gearing, and for about $15 bucks, and a master link or two, I can change the gearing in about 15 minutes. Over all, I like the set up. I went up the street yesterday, and it was whisper quiet except for the tires humming. A car went buy in the other direction, and they were staring because "there is no motor". All as you can see is the square battery pack where the motor used to be. When I came driveway and jumped off a snow bank. It was a short ride, but it was fun and inspiring.

Hey John. I meant to comment on your battery placement. The front veiw reminds me of a BMW with the cylinders hanging out. As odd as it may look, the protrutions have been proven to be ok for years by BMW. The low CG will be helpful as well.

Mike K.

Hey John
I was able to complete the installation of the jack shaft and the new gearing today. We rode it up and down the street a few times. What a nice package this is turning out to be. We found a bad battery in the string, and I think that was causing the "no torque" problem. I pulled out the battery and hooked up the pack so it is now 36V. Without the bad battery, it has more power and acceleration than the 48V with the bad cell. Very encouraging! I am looking forward to a healthy 48V ride!

John, the way I read the kelly controls diagram.. reverse is just a switch you connect to that spade connector marked REV. It's extremely simpler than reverse on other controllers which rely on different external switches or reversing contactor to reverse connections to the motor. You can simply ignore stuff you don't need - such as the reverse mode, since that's rather unnecessary for a motorcycle.

I haven't done anything approaching a final wiring - what I set up the other day was a quick test that skipped over a few of the safety steps, like there are no fuses, no precharge resistor (because there's no contactor), etc. I don't remember the wiring diagram right now and I'm 2,500 miles from home so it'll have to wait a couple days.

Hey Guys.

Looks like you answered the reverse question amongst yourselves. I did hook up reverse (just a simple switch) as it comes in handy with a 4-wheeler. I also like the 1/2 speed option in reverse.

I mounted the motor the same way it was mounted in the Elec-Trak. It sits in a "V" cradle, and is through bolted to the motor housing.

I added (4) 12V-24AH batteries today, and changed the gearing. I love this thing! I can't wait to let others ride it.!

I was just sitting here thinking, and I may try to use reverse as a second speed in forward, to slow the thing down while in the woods, or towing a trailer around the yard. If I swap the motor leads, I can give it a try. It could be a two speed controller type thing. If I am thinking correctly, I may even be able to do it with switching and contactor.

The pictures are of the latest gearing nad battery set up.

Hey John, the gearing hub and sprocket came from Tractor supply. Another good place to go "to engineer on thy fly"

fOR THE LOVE OF GOD! why on earth did you destroy a perfect cb 750? for this experiment? why not a peice of crap suzuki or a yamaha? DUDE!