‘79 Kz650B - Semi-Trackbike Build

Been waiting on fork bushings for a GL1800 so jumped back on the Kz for a little bit. Like I’ve mentioned before, I’m trying to work from front to back as much as possible.

The tach that came on the bike had a fuel level light, but the B-model I has no fuel level sensor. So I dug through my stash and found the brand new Stack tach leftover from the Gpz project. A trip to Yahoo Japan and I now have a special mounting bucket to mount the tach to a Z1/Kz gauge bracket.



Final mock-up is done. Some better harder, refinish the speedo housing and gauge buckets, and a few other bits and I can call the front end done.



Also modded the tach bucket to put the reset button where the tach cable would pass through.


Later, Doug
The GW is done so I swapped the Kz back on the lift.

Long ago I broke off the three bolts that hold the small chain guard plate to the transmission cover. I didn’t really want to remove the cover, drill, extract, tap etc or even replace the cover. I pulled out the welder and found some sacrificial nuts. A half hour later and the three bolts were out.

Later, Doug
A bit more done. Bought a used set of 3ohm Dynatek coils to go with my DynaS. They came with some dirty red Taylor leads. I never liked the look of Taylor boots anyways, so I opted to buy a set of 7mm suppression core wires from Dyna. I also made some wires to connect the coils to the main harness and covered them in harness wrap.




Later, Doug
nice. What ignition are you planning on running?
Along side my B3, my dad’s Kz650C2 has been sitting a few years. I cleaned and rebuilt the carbs a couple years ago, but robbed a few O-rings and never installed the carbs back on his bike. I thought it was the perfect opportunity to test fire up my B3 as I bought O-rings to rebuild the extra set of carbs I bought for mine. So I took three of the O-rings allocated for my carbs and installed on his. Bolted everything up and hooked up the auxiliary tank and poured some gas in. Number 2 carbs started a slow drip from the overflow but nothing significant. I hooked up the battery and….no start. Cranked it for a bit and still nothing. Unplugged #4 plug wire and used a spare plug to check for spark. I had decent spark, but I only bolted the DynaS up and didn’t really check timing. Out came the timing light. Clamped around #4 plug lead and turned on the light. F 23 showed on every strobe flash. The timing mark lined up though. So I reversed signal leads in the coils. But it was too late, my battery was too weak to spin the engine fast enough to catch. Then the #4 carb started dripping. I took the carbs back off, pulled the bowls, and blew through the drain tubes. Sure enough both were cracked. So I’ve sourced and ordered some brass tubing to sleeve the tubes. As soon as the brass tube comes in, I’ll repair the overflow tubes and try again. I also went ahead and rotated the Dyna rotor 180° and swapped the coils’ signal wires back.

Later, Doug
My brass tubes haven’t arrived yet so I found my flux, solder, and propane torch yesterday and sealed up the two drain tubes that were leaking. I then reinstalled the bowls and the carbs to the bike. It took a bit of time, but I got it to start on full choke finally with no leaky carbs. It didn’t want to idle off choke so I “throttled” the engine with the choke lever. Finally the battery gave out again after a bunch of cranking. While the battery was on the charger, I checked fuel levels using the hose and adapter from Z1 Enterprises. Three were the same with only the #3 being a little lower. 1, 2, & 4 were around 4mm (going by my eye-crometer). I put the fuel IV bottle away and pulled the old B7ES plugs to have a look. 1 & 3 looked decent, but 2 & 4 were wet. I noticed #4 was running cooler earlier on so that made a bit of sense. The #2 pipe was hot to touch though. I started looking at the carbs closer….turns out I forgot to cap the vacuum port for the fuel tap on #2 carb. D’oh! I also pulled the #1 bowl as it’s easy to get to so I could check the pilot jet to check for clogging. It’s brand new and I could see light through it easily. I had cleaned and rebuilt the carbs a few years ago, let them sit and had forgotten I installed the pilot jets as the old heads were pretty scarred.

As it stands now, the battery is on the charger, a fresh set of BR7ES plugs are in, fuel level is roughly set and air screws are 1.5 turns out instead of 2.5 like I originally had them set at.

Any advice?

Later, Doug
have you verified you're getting 12v to the coils? the switches on these bikes corrode pretty easily if left to the elements.
have you verified you're getting 12v to the coils?

I haven’t verified but I’m running the “Wired George” coil relay mod as I swapped to Zx14 switches and know their smaller wires cannot handle the amps like the stock Kz switches do.

Later, Doug
I attempted again last night. I found quite a silly thing I overlooked and eventually the source of my frustrations.

Silly thing: I had not fully seated the header pipes. #1 & #4 were seated, but I did not tighten the inner two cylinders which caused massive exhaust leaks. I tightened up the nuts and finally got the bike to somewhat idle.

I got the bike to idle roughly around 1500rpm. I say roughly as my electronic tach does’t start on a finer scale until 3k. The 1, 2 and 3 are very close together. I should have hooked up the stock cable driven tach for a better reading. (I’ll do so next time.) I got out my sync gauges and went to hook them up. I misplaced the vacuum caps for the inner two cylinders so I grabbed some generic ones I had laying around. Turns out they were a bit loose and were pretty easy to pull off. Possible vacuum leak there. Anyways, I hooked up the gauges, started the bike and the gauges read….ZERO! All four cylinders did not move their gauge. That made me scratch my head. Until I got out the starting fluid. A spray at each boot/head joint spiked the RPM’s. The boots were still pliable, but the flanges have rather deep indentations of the head’s mating surfaces. Before the initial install, I smeared a thin layer of Yamabond-4 just in case. Apparently, it wasn’t enough. I took the carbs back off again. On #1 cylinder, I sprayed brake cleaner at the joint with the nozzle about 1/8” away and looked into the port. I could see the spray coming through. Ugh!

So I either need to buy another set of carb boots of figure out a way to seal the existing ones up. I really don’t like the idea of globbing on sealant.

The struggle continues….

Later, Doug
I've never been upset when I bought new carb boots.
After a bit, I figured out how to chuck the boots in the lathe. I skimmed the rubber off the outer mounting flange but left the inside alone. If it doesn’t work, I’d need new boots anyways so I’m not out anything so far. I did do another smearing of the Yamabond and have let it sit for a few days now.



I figured it was a good time to finish the exhaust system as the open header is a bit loud inside a garage (Although I don’t think the Danmoto muffler is going to muffle a lot.) Made a mount and currently waiting on SS tubing to arrive to connect the header to the can.




Later, Doug
since you were chucking them in the lathe you could cut a groove for an o-ring. like suzuki does.
Since I’m running the rearsets, the kickstarter is useless now. I removed it which leaves the shaft exposed. Not wanting to leave it that way, I machined up a nice aluminum cap.








Later, Doug
My new SS midpipe for the exhaust system arrived yesterday. I was able to use my new-to-me TIG for the first time since I bought it a few years ago. I tacked the joints without filler. (Also my first time using a TIG ever!). I had a couple spots blow through but that happens. I plan on shortening up the midpipe by an inch or so.







Later, Doug
good on ya for getting on the TIG train! a littel tricky to learn but for the type of work you are doing you will love it.

No offense intended but your tacks look super oxidized, what is your setup? I usually use at least a #10 cup with about 25-30 cfh for stainless. preferably a 12-14 cup. A gas lens helps with gas coverage too. You can get away with out back purging stainless sometimes but its always recommended to back purge. I have also used Solarflux when i didn't want to back purge, doesn't weld as nice though. keep after it. This project is fueling my track bike build that is progressing at a snails pace.
I was using a #7 cup and #10-15 cfh. (It’s hard to tell as it’s low on the scale). I ran 63amps as I heard 1A per .001”. However, I think some people use less amps for SS due to the HAZ. I did not back-purge although I did buy a dual flow meter to do so. I will use it when I really weld it.

Any other tips?

Later, Doug
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