‘79 Kz650B - Semi-Trackbike Build

The bike came with a black, at one time long ago, Kerker exhaust. The megaphone always looked low to me since I brought the bike home. So I found a used MAC(?) 4-1 header and picked up a brand new Danmoto muffler for reasonable prices of off FeeBay. I had some left over exhaust piping from some other project that I used for mock-up. Initially, I tried to follow the rear frame rail but the more I see it the more it reminds me of a diesel semi’s smoke stack.


So I’m thinking that it needs leveled out a bit. I have poorly sketched two angles.
1) Run the exhaust so it’s parallel the the bottom of the tail section.

2) Somewhere in between.


Later, Doug
Parallel to the hard edge of the bottom of the tail is number one for me. Where you started with it parallel to the frame rail is a close second. The somewhere in between option would require some strong parallel graphics on the tank to work for me.
what is the ground clearance like with it parallel?
what are you doing for footpegs/brake lever/rear MC? there is a interference potential there with rearsets and the exhaust mounted higher
what are you doing for footpegs/brake lever/rear MC? there is a interference potential there with rearsets and the exhaust mounted higher


I have a set of aftermarket rearsets meant for a Sv650. I loosely hung the right side and it looks like interference is inevitable with the mockup midpipe in its current position.


I’m putting the exhaust on hold until I finalize the rearset’s mounting position.

So since I have my bird’s nest of wiring, I decided to focus on a battery and battery box. The stock battery box was “modified” by someone previously to make it deeper for a taller battery. It’s pretty rough so I decided to fab one from scratch.


I started with building a box around a YTX9-BS as I had a weak battery from my 900RS. After cutting, bending and duct taping I had enough of a box to fit to the frame. It looked like it’d work until…I realized that the terminals are reversed and the 9 is a bit wider than the YB10 that came with the bike. This leads to some fitment issues.



Now I’m pondering a smaller battery in both size and capacity. Thinking maybe a Ytz8 or even a 7. All lights will be LED with the exception of the headlight. The biggest draw will be the coils.


Later, Doug
Common problem on the exhaust/rearset issue. Since you got the means, it might be nice to make some plates that will allow for some location adjustment of the footpegs to dial in the ergos.

Maybe consider a lithium battery since this is a track/racebike? The draw back is you will need to change the charging system to 3 phase to work with the lithium battery to keep it from going boom. Its pretty easy as the 3 phase KZ750E stator drops in, then all you need is a lithium specific reg/rec. I did this swap on a 78 KZ650 a few years ago, it was pretty much plug and play, however i didnt go to lithium so I used a OEM R/R off a late model Z650. Im currently trying to figure out how to swap to 3 phase on my 750twin so I can run a lithium battery, it will be much more involved unfortunately.

Are you going to go full loss battery for trackday/race? removing the rotor off the crank will take like 5 pounds off the rotating mass which should equal more HP and faster revs
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I’ve thought about total loss and going kick-only. My worry is there will be kick lever/foot peg interference issues, unless I get creative with a torch to the kick lever. And I want street-ability so lighting may be an issue.

I have an e-mail in to Rick’s Electric as I do have 4 various sizes of Shorai’s sitting on my shelf. That’d probably be the way to go it I can find a compatible regulator for the stock single-phase system.

Later, Doug
On my KZ1000 I have a folding footpeg and a rotating brake lever system that allows me to rotate the brake lever back out of the way while kicking starting. Works good, required no modification to the kickstarter, but i did anyway because the high compression was bending the lever. if you check out page 4 here there are some photos of the assembly - but this was before i added the folding footpeg. I got rid of the pin to stop it from rotating back while riding as i found i didnt need it.

It is my understanding that a single phase charging system will not work long term with a lithium battery. Earth-X plainly states as much on their website. However, I am not an electrical guy and just repeating what I have read there. I would be interested if you find a solution for lithium to charge with single phase power as it will save me some hassle with my 750G.

"Are Vintage Single Phase (or Magneto type) Charging Systems Acceptable for Charging a Lithium Battery? The quick answer is no...."

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Thanks Doc_rot. The rearsets I have do no fold up, although I’m sure I can find pegs that do. The pegs are held on my M8 threads so should be relatively easy to source something.

While waiting for a response from Rick’s, my package of 1/8” aluminum sheet drops were delivered. I was able to shape my second front fender mounting plate. Since both mounts are done, I can cross that task off my to-do list.






Later, Doug
I called Rick’s today. They said the returned my e-mail but I’ve been flooded with SPAM e-mails so I may have missed it. Anyways….Amber confirmed that 14-304 is compatible with the single phase charging system and made for lithium batteries only. She noted it has 4 wires: 2 to the stator, one ground and one power feed.

It’s ~$135 and can be found at here.

Later, Doug
Interesting. I wonder if it has some type of ripple smoothing as that seems to be the main issue with the single phase and lithium charging rather than the voltage output. EarthX is saying less than 1.5V delta in ripple.
I wonder if it has some type of ripple smoothing as that seems to be the main issue with the single phase and lithium charging rather than the voltage output. EarthX is saying less than 1.5V delta in ripple.

No idea….:dunno

Someone on a 650 only forum said the stock R/R is fine but I’m still hesitant. Maybe if they offer to pay for a replacement Shorai I may leave it? Lol

I kept thinking about a battery box solution for one of my Shorai’s and then it dawned on me, I’ll just mod the stocker since it was already butchered once before. I ended up cutting about the bottom half off.




Then I made a rectangle with the same inside dims from 18ga sheet. Four tack welds and set everything in place.




I’ll need to find a shorter band. I bought a used OE one but it’s too long. I may drop the hook plate down some too.


Later, Doug
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Nice save.


I’m pondering trimming off another 1/4” or so so only a little bit of the original battery box hangs below the new bottom.

Somewhere I have a modern-ish fuse block that uses ATC fuses rather than the old AGC glass fuses. I’ll have to do some digging through my storage tote of electrical components and wiring.

Later, Doug
Agree with your observation about the smoke stack. It just needs enough uplift to avoid touching the ground at excessive lean angles.

there are a few good fuse options if you plan on rewiring it. I used a PC8 from Easternbeaver.com, but Matthew at Sparckmoto.com designed a neat unit with fuses and I think it has a relay built in which would make it perfect for the ignition circuit. http://sparckmoto.com/Products/Detail/89
I’m planning on more of a renovation rather than a complete rebuild of the harness. The two units you mention look WAY overkill for no more than planning. I’ll look into them a bit more. I know something like a M-unit is definitely not needed.

Later, Doug
Not much progress as of late. I’ve been busy making forward controls and slamming the back of a Honda Magna with rigid struts. (Don’t ask!)

I finally bought some nice braided split loom harness wrap. I HATE the corrugated plastic stuff you get a the local car part stores. First order was to make the used DynaS ignition look a bit better.





I plan on treating the rest of the harness to the same process. I also found the newer style fuse block to replace the old school 3 glass fuse setup. It’s setup for five circuits so I will have enough.

Later, Doug
Last night I cut off and repositioned the battery strap hook.


Next was mounting the new fuse block. It was slightly wider than the battery box so I welded on a couple nuts to a flat bar and then welded the bar to the box after removing the original fuse box mounting tab.




Later, Doug
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