1979 Yamaha XS750 conversion.

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biothundernxt   1 mW

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1979 Yamaha XS750 conversion.

Post by biothundernxt » Jun 30 2020 12:59am

Alright, lets get this thread started.
I recently acquired the aforementioned XS750
I will add pictures later this week.

I have ordered the following parts:
17" by 6" 12kw rear hub motor from qsmotor (configured for 145kph)
300a ANT bms with screen.
Kelly KLS96601-8080I
A 220v charger for 96v lithium at 20A

I already have lying around:
A pile of matched nissan leaf batteries to make my battery
The bike itself

Things I still need to get:
A replacement swingarm that will accept the new wheel (stock XS750 is shaft drive)
Brakes for the rear wheel
J1772 adapter to feed the charger
throttle (considering a domino pot throttle if i can find one)
Dcdc converter (suggestions welcome)
Main power contactor


I did some looking about but I could not find any mention of anyone using this motor. I plan to document my entire build process thoroughly with lots of pictures and data.
There is a local place that is willing to let me use their dyno too when I get it put together.

I don't expect this to be a drag strip monster, but having some actual data out there should be informative.

Does anyone have any experience fitting brake rotors to these motors? I am trying to find a suitable brake rotor/caliper setup that will fit onto the existing mount holes for the motor.

Any other suggestions are welcome too.

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amberwolf   100 GW

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Re: 1979 Yamaha XS750 conversion.

Post by amberwolf » Jun 30 2020 6:41am

biothundernxt wrote:
Jun 30 2020 12:59am
throttle (considering a domino pot throttle if i can find one)
You may wish to consider a cable-operated-throttle (COT), using whatever cable-type grip you like, or that it already has, and simply run the cable to a COT module inside the housing with your other wiring and electronics. Then there's no weatherproofing worries, etc., for electronics on the handlebar control.

LIke the one used here:
viewtopic.php?f=2&t=100859&p=1475133&hi ... e#p1475133
(see MJSfoto1956's build thread for pics of it in use on the bike)
or here, where I use one operated by a brake lever for proportional regen,
viewtopic.php?f=2&t=67833&p=1562688&hilit=atv#p1542626
or here, where I use one operated by an ATV thumb throttle as the actual system throttle
viewtopic.php?f=2&t=67833&p=1562688&hilit=atv#p1562688
I did some looking about but I could not find any mention of anyone using this motor.
Which specific motor model is it? You only give this info:
17" by 6" 12kw rear hub motor from qsmotor (configured for 145kph)
Does anyone have any experience fitting brake rotors to these motors? I am trying to find a suitable brake rotor/caliper setup that will fit onto the existing mount holes for the motor.
A number of the Chinese hubmotors use various Chinese rotor "standards", and some are even company and motor-model specific, with no source for them anywhere else (I have a bicycle motor from Fusin like this, and the company is long gone).

So your best bet for a rotor is to get it with the motor, if the rotor mount on the motor doesn't match standard motorcycle rotors you can just go out and buy. It should still work with any caliper that can accomodate it's thickness, mounted so it works with the diameter of whatever rotor it is.

biothundernxt   1 mW

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Re: 1979 Yamaha XS750 conversion.

Post by biothundernxt » Jun 30 2020 10:12pm

I had considered using a throttle setup like that, but I have (possibly unfounded?) reliability concerns because the stock throttle is not dual cable.

This is the motor:
https://www.qsmotor.com/product/17-inch-12kw-hub-motor/
I don't have a model number.

For variable regen, I plan to use some kind of strain gauge on the rear foot brake. I havent figured out the details yet, but I am sure emulating the potentiometer input for that with a microcontroller based on the output of the strain gauge should not be too hard.

Thanks for the info on the rotor. That does not bode well for down the line when I need a new rotor...
I plan to keep this bike for a very long time.

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Dui, ni shuo de dui   1 kW

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Re: 1979 Yamaha XS750 conversion.

Post by Dui, ni shuo de dui » Jun 30 2020 11:08pm

biothundernxt wrote:
Jun 30 2020 10:12pm
I had considered using a throttle setup like that, but I have (possibly unfounded?) reliability concerns because the stock throttle is not dual cable.
These cable throttles are real nice, never had any issue with them, you can go for it. Feeling is great too.

I suggest you to use one for the variable regen too, you can actuate it with a cable lever on the left handlebar since you won't have a clutch to actuate anymore. That's how we did it on a friend's bike, it's real nice to use and you keep the mechanical brake on the foot for safety in case something goes wrong with the electrics.
biothundernxt wrote:
Jun 30 2020 10:12pm
This is the motor:
https://www.qsmotor.com/product/17-inch-12kw-hub-motor/
I don't have a model number.

I don't know anyone using a 12KW motor, but I know people using a 8KW motor and I'm myself using a 3KW motor. There's not much difference aside from the power they can tolerate, so finding someone who has exactly the same doesn't really matter.
You can expect some serious power with that, I tried the 8KW and coupled with a good controller it isn't weak at all.

Fitting brake rotors is pretty easy, just bolt it on there, the holes are already in place. You can find some kits on aliexpress for cheap. You don't need a powerful setup on the rear brake anyways, you'll have the regen so that's mostly dead weight. Just need it for safety and at very low speeds.
biothundernxt wrote:
Jun 30 2020 10:12pm
I plan to keep this bike for a very long time.
Yeah QS motors are quite reliable usually.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

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amberwolf   100 GW

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Re: 1979 Yamaha XS750 conversion.

Post by amberwolf » Jul 01 2020 10:28am

biothundernxt wrote:
Jun 30 2020 10:12pm
I had considered using a throttle setup like that, but I have (possibly unfounded?) reliability concerns because the stock throttle is not dual cable.
None of these COTs are dual cable either, becuause they have an internal spring return.

A dual cable pulls boht directions, which with a mechanical ICE throttle might be a necessary thing so a spring can't fail and leave the throttle stuck open with gas pouring thru. Not an issue with electric motors--you just turn off the power. ;)

For variable regen, I plan to use some kind of strain gauge on the rear foot brake. I havent figured out the details yet, but I am sure emulating the potentiometer input for that with a microcontroller based on the output of the strain gauge should not be too hard.
You could use a COT for that, too, adding a cable pull to the foot brake, and a cablestop above it on the frame. Much simpler, and a proven electrical design. ;)

Alternately, since you won't need a clutch anymore, then if it has a clutch lever on the left side, you can use the clutch lever and cable to control the ebrake.

Looks like it uses a 3-bolt rotor design, so you would need to find a rotor with that many bolts in the right BCD (bolt circle diameter). I don't know what that is, because the page doesn't say. It just sayd "11) Brake: disc brake (220mm)" which is the outer edge of the rotor, not the BCD.

A simple search for 3 bolt brake rotor turns up a fair bit, don't know if any of them are the one you want
https://www.google.com/search?q=3+bolt+brake+rotor

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Re: 1979 Yamaha XS750 conversion.

Post by biothundernxt » Jul 06 2020 1:37pm

I have been contacting a few suppliers from china about getting brake parts that will fit.
I will post here with some more info when I have confirmed a fit.

But now for those other photos I promised earlier!
Here is a picture from the day I picked it up:
TuojwY2-min.jpeg
TuojwY2-min.jpeg (494.09 KiB) Viewed 117 times
I fitted one leaf module various ways to see how it might fit:
vq8MmKo-min.jpeg
vq8MmKo-min.jpeg (415.21 KiB) Viewed 117 times
nU6zliE-min.jpeg
nU6zliE-min.jpeg (475.47 KiB) Viewed 117 times
And here is my progress so far disassembling the bike down to the frame.
TK7q3Uj-min.jpeg
TK7q3Uj-min.jpeg (481.71 KiB) Viewed 117 times
HFs203d-min.jpeg
HFs203d-min.jpeg (417.09 KiB) Viewed 117 times
I finished up the battery the other day:
puJreUw-min.jpeg
puJreUw-min.jpeg (485.92 KiB) Viewed 117 times
I have a lot of restorative work to do.
I have a 3d printer and scanner, soI plan to scan in models of most of the parts as they are, and then sell the tank/plastic pieces to someone who wants to restore a stock XS750, and then print out replicas of the plastic parts and a shell of the tank for looks (I will likely put the charger inside the tank.
I'll post the models I scan if anyone is interested.

Today though, I am off to find a new swingarm so I can mount that monster 12KW motor.
Attachments
g0fvaV4-min.jpeg
g0fvaV4-min.jpeg (454.45 KiB) Viewed 117 times
Last edited by biothundernxt on Jul 06 2020 9:48pm, edited 1 time in total.

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amberwolf   100 GW

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Re: 1979 Yamaha XS750 conversion.

Post by amberwolf » Jul 06 2020 3:30pm

I don't see any pics; presumably you're using some external site to host them that isn't visible to everyone. (a common problem).

I'd recommend attaching all images directly to your post using the attachments tab, since if they're uploaded to the forum they'll be visble to anyone that can see your post, and wont' disappear whenever the external hosting site goes down or changes their mind about who gets to access the content the users posted there. :/

biothundernxt   1 mW

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Re: 1979 Yamaha XS750 conversion.

Post by biothundernxt » Jul 06 2020 9:23pm

Interesting. I used imgur. I will edit my post and try to change that.
Edit:
Completed

biothundernxt   1 mW

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Re: 1979 Yamaha XS750 conversion.

Post by biothundernxt » Jul 07 2020 12:20am

Nobody local had anything available, so i ordered a Yamaha fazer swingarm.
$_57.jpeg
$_57.jpeg (193.55 KiB) Viewed 107 times
I hope it fits. Some other conversions from shaft to chain for the xs750 used this swingarm, so fingers crossed that it will not require much modification.
We'll see. It should get here pretty quick, it is only going across town.

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Re: 1979 Yamaha XS750 conversion.

Post by biothundernxt » Jul 07 2020 12:31am

Also, here are some pictures showing a cardboard mockup that is the size of my battery floating around in my frame.
I'll need to make a box for this to sit in, but this looks promising so far.
IMG_20200706_153354_compress95.jpg
IMG_20200706_153354_compress95.jpg (451.86 KiB) Viewed 107 times
IMG_20200706_153410_compress48.jpg
IMG_20200706_153410_compress48.jpg (451.64 KiB) Viewed 107 times

LeftieBiker   10 kW

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Re: 1979 Yamaha XS750 conversion.

Post by LeftieBiker » Jul 07 2020 2:36am

Try turning that rectangular mock-up on its wide side, then leaning it down in the front of the frame. That will give you a better, lower center of gravity, and leave you room for the motor behind and slightly above it.

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Re: 1979 Yamaha XS750 conversion.

Post by biothundernxt » Jul 07 2020 5:40pm

LeftieBiker wrote:
Jul 07 2020 2:36am
Try turning that rectangular mock-up on its wide side, then leaning it down in the front of the frame. That will give you a better, lower center of gravity, and leave you room for the motor behind and slightly above it.
The motor is a hub motor, so there is no advantage there, but a lower center of gravity is always better. I will move it around some more to see what the best position would be.

soyachips   100 µW

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Re: 1979 Yamaha XS750 conversion.

Post by soyachips » Jul 11 2020 7:18am

I recently converted a 1989 Yamaha FZR250 using a QS 273 6000W v3 motor, very happy with the results and happy to answer any questions you have. For the brake rotor I got QS Motor to supply one as it seemed like an unusual bolt pattern. To get the motor in, I extended the slots to make dropouts and made some solid aluminium blocks that slide into the back of the swingarm and clamp onto the axle flats. There will be a lot of torque on the axle (especially 12kW!) so you’ll need a good way to resist that force. Also I tried to use the original rear brake caliper but didn’t allow for the bulk of the hub motor so ended up buying a thinner one and getting a new mounting bracket made. The Fazer swingarm in your photo looks a little different to mine so not sure how useful my 3D models would be but happy to share if want. Good luck, looks like a great project. Those Leaf cells should be amazing!

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Re: 1979 Yamaha XS750 conversion.

Post by soyachips » Jul 11 2020 7:22am

Also very interested to see how you go with the Ant BMS, especially how you connect up the power cables to handle a lot of current.

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