And so it begins... 1976 KZ750B Twin barn find project.

Good morning motorcycle fans. Today I'm starting in on the $300 1976 Kawasaki KZ750B I picked up from a local classified ad. It's got just under 14,000 miles on it, and from what I've been told has been sitting in a barn for the last 30+ years. I hosed it off when I got it home a couple months ago and now that the holiday season has past I'm going to see I can get it running before deciding what direction to go with restoring and/or customizing it.

Here's what I know so far. I pulled the seat, the battery and tank to start. The battery is junk (to be expected). The gas tank had minimal fuel in it I believe when parked. There's a little brown sticky turpentine smelly goop in the very bottom, minimal rust, and it looks to have had some sort of tank liner in it at one point in time. I'm not too concerned about this yet, because I don't know if I'll run this tank. The good news is that with some minimal work, I think the tank could be usable once again.

Next I pulled the plugs and did a cold compression test. Both left and right plugs look very good, certainly not a bad sign but too early to tell. I hooked up jumper cables to my car battery to see if the electrics and starter worked. The start button didn't do it's thing, lighting seems weak, the "stop/lamp" indicator on the cluster is flashing, many hand switches are seized, but shorting the starter relay with a screwdriver did get it to turn over at a seemingly slower pace. Left cylinder compression peaked at 120psi, right cylinder peaked at just over 110psi. The engine rebuild magazine article found in the KZR filebase says 100psi minimum compression (hot), with max difference of 14psi. So, with that info I guess I'll keep pushing forward.

That's where I'm at for the moment. It's got it's fair share of problems. Both master cylinders are dry and ugly. The rear brake drags. Electrical issues are unclear so far. My first thought is to see if it will run. Still need to check spark. I'm 99.9% sure the carbs are gummed up from what I've seen in the tank, and the fact that the fuel petcock arm is broken off and stuck in the "On" position. I'll probably pull the carb tops first and simply check the diaphragms and slides and see what it looks like in there. If'n it's ugly, I recon I'll pull the whole carb assembly to see what's up.

I don't really have a vision for this thing yet. It was cheap, and I was looking for something interesting to tinker with. I like parallel twins in many forms; stock, cafe, and even bobber/chopper design as seen with many Yamaha XS650 twins. I figure this thing has similar potential, and I've seen some cool builds KZ750 twin builds online and in this forum. This is my first in-depth build with Japanese parallel twin, but I've had previous experience with other extensive motorcycle builds. I've been poking around this forum as much as I can, but any advice is sure appreciated. I'll do my best to keep this thread updated with progress.

Thank you to all who contribute and manage this forum. Such a great resource for keeping these older motorcycles alive.

Cheers,

-David

Welcome to KZRider
I fixed your pictures . Next time hit the insert all tab to finish loading them.
Dave

Thank you. Still learning the ins and outs of this forum. I also posted this thread twice because I didn't think the first one posted. Could someone please delete it?
-David

soulsrgn wrote: "I hooked up jumper cables to my car battery to see if the electrics and starter worked. "

I sure hope the car was NOT running when you did this as that can destroy the bike's electrical components. Best bet is to buy a bike battery, but if you ever intend to jump start the bike from a car or truck make sure the car or truck is NOT running. Ed

650ed wrote: soulsrgn wrote: "I hooked up jumper cables to my car battery to see if the electrics and starter worked. "

I sure hope the car was NOT running when you did this as that can destroy the bike's electrical components. Best bet is to buy a bike battery, but if you ever intend to jump start the bike from a car or truck make sure the car or truck is NOT running. Ed

Thank you, Ed. No, the car wasn't running, but very good advice.

I'm currently working on a similar project...a 650. I'm looking forward to seeing how you approach yours.

Carbs...

I took off the air box boots and reached in with a finger to discover both slides were gummed up and stuck. So off came the carb assembly.



Upon inspection my first suspicion was correct. Everything was pretty gooped up and gross. Time for a good cleaning.













I did a pretty thorough cleaning job on it; scrubbed and cleaned all parts and as much of the body as I could with brushes, penetrating oil, solvent/cleaner, and compressed air. The slide diaphragms are in good shape, and still surprisingly pliable. I didn't change any adjustment settings in hopes that it was running when parked.







Now the carbs are back together, much cleaner, and all moving part seem to move freely and normally. I'm not a huge fan of CV carbs. I prefer mechanical slide carbs for throttle response, and I find them to be a simpler design for tuning. However, these are what came with it, and I've seen people in this forum support them for their performance on this model. I'd love to hear your opinions and experience with these carbs, and/or other possible replacement options. Now to get them back on the bike and check for spark.

-David

P.S. Quick update. No spark. That will be the next troubleshooting step.

No fuel, no spark, but you have compression. One out of three isn't bad for 30 years!

Good morning motorcycle fans. I last left off going through the carbs with a quick scrub down and blow out, and then discovering that there was no spark. Well, I've done a few things since then, but not much.

First, I checked to see if there was power going to the coil with a simple test light. Good to go there...



Then I pulled the points cover to have a look. These photos are after I picked and poked at some of the corrosion around the points contact, and cleaned the contacts with some emery cloth...





It was at this point that I decided to suck it up and order some parts. I started at to local motorcycle parts counters, to which I discovered that they stocked very little for older stuff. I do my best to support local shops, but in this case I turned to Z1 Enterprises, and advertiser on this page. I ordered a basic lead acid battery, points, condenser, some fuel line, and a couple carb kits.

While waiting for parts, I started researching ways to clean out the gas tank. That lead me to remove the petcock to prep the tank for a wash. This is that discovery...





Looks like I'll be ordering a fuel petcock as well. There are some in expensive replicas out there for under $20 (OEM part #51023-055 and 51023-043) if you look around. I'm still on the "will this thing run and drive" budget, so I'm trying to be frugal until I am confident this bike is worth dumping money into.

I'm using this thread not only to document my journey, but my budget as well. Here's where I'm at so far.

Purchase Price - $300
Battery, Fuel Line, Carb Kits, and Points and Condenser (+shipping) - $140

Today I'll be picking up some things locally to clean the tank and other parts. I think I'm going to try the vinegar and Marvel Mystery Oil technique as seen in this video I found on YouTube, and diluted Hydrochloric acid (Muratic acid) for some of the aluminum parts I need to clean.

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I know this thread may be starting out a bit elementary for many users of this forum, but I'm simply trying to document my battle for others who are wrestling with similar demons. This particular motorcycle is in the worst shape of any motorcycle I've previously worked on. I feel like I'm gambling a bit on this purchase, and I am trying to be budget conscious with out getting completely upside down on something that may never ride again. Some of the labor and cleaning techniques I am or will be using are new to me. I'm open to constructive feedback, and feed off of the experience of others. Thank you for your advice in advance.

-David

I totally get just trying to make it run but FYI the stock ignition system on the 750 B is pretty lazy. if you can find the electronic ignition setup from a late model 750 twin or a 440 twin the bike will be way happier with more timing and more advance.

If you haven't read my build thread you should go look at what I went through cleaning out a rusty tank. Depending on how bad it is, it can turn into a lengthy ordeal. From the look of those rust flakes you may be headed down a similar path. My bike sat outside for 28 years, so it too was in the worst shape of any machine I have worked on. The one thing I learned was using a water rinse would cause flash rust on an otherwise cleaned interior. I ended up switching to an alcohol rinse to avoid this issue. I also ended up needing some weld repairs and had to use a sealer afterward. Best of luck! My bowl of popcorn is ready for your journey!

Take a boo at this video from Johnny's on tank cleaning. I've had good experience with Metal Rescue, though I haven't had to use it in a tank.