Saving a '81 KZ750-E

I'm new to this forum, and really glad I found it! A lot of good information and resources. I had a friend gift me a 1981 KZ750-E last year that has been sitting outside in southern California for the last 28 years. He was the original owner and logged 34K miles on it before parking it in his back yard. The sun has taken it's toll on the bike, and the insects decided it was a great place to start a commune. My plans for this bike is a resto-mod, with a vintage Superbike theme. I will be using the front end from a 2005 Honda CBR600-RR. After modifying the steering stem, I was able to press the KZ stem into the Honda lower triple clamp. The front end will now bolt up to the KZ frame using stock sized bearings.

Currently I have the bike down to the frame, and the top end of the motor is at the machine shop. Several valves were stuck, so a complete cylinder head rebuild was in order. I was referred to RTC Engineering in Florida during my search for new pistons and rings, and they had a set of 10.5:1 racing pistons left on their "old stock" shelf. This was a stroke of luck, since I was having trouble locating pistons that were 67 mm in diameter. I am debating on leaving the bottom end intact and just going with the top end rebuild.

I am working on adding a swing arm brace to the stock swing arm. The brace will be 1.50" dia. x .090" wall tubing. I made a weld fixture to keep the swing arm straight. I have the tubing bent, but have not started trimming it to fit yet.

Welcome

Welcome to the forum! I'm always amazed at the fact that some folks basically abandon their bikes and let them sit unused for decades. A guy close to my house had a Honda chained to a tree for about 25 years, but eventually he moved and I guess sold the bike. I'm glad you're going to bring that KZ back to life! Ed

Here is the weld fixture for the rear swing arm. 1/4" steel plate, with 3/8" thick angles

I just got the cylinder head and cylinders back from the machine shop! All new valves, guides, seals, seats machined, mating surfaces trued, rings gapped. etc. Now I just need to decide on going with the used bottom end, or jumping all in and splitting the cases and see how it is. I haven't researched the availability of internal engine parts yet.

Started to fab the swing arm brace this weekend. Coping the ends to get a good fit for welding will be a bit tricky, and I only have one tube bend to work with. So I am using paper towel rolls and toilet paper rolls as templates. A lot cheaper to screw those up first, then when I get it how I like it I will trace the shape onto the tube.

Welcome. Another KZ saved and I like where you are going with it...

Just finished fitting all the brace tubes, and it's ready for tack welds.

That brace turns out really nice

/A

Following! Nice swingarm...

subscribed!

When I started to fab this swing arm brace, I had to make some assumptions. The main one was to follow the profile and width of the original swing arm. All I had to go off of was pictures from the side on existing bikes. In the back of my mind I was wondering if there would be enough clearance for the chain. Well, I got it tacked together, and fitted it to the frame yesterday. Total failure! Glad I only tack welded it together, because now I have to cut it all apart and start over again. I am thinking the width needs to increase at least two inches to create the space needed for the chain to clear. Unfortunately my tube bender will not go past 135 degrees, so I had a friend bend the piece I used to mock this brace up. I will need to split it on center line, add a piece, and weld it back together again. If it comes out looking like Frankenstein I will at least have a better mock up to start a new tube bend. The other issue I did not get right is the section that joins the brace tube to the original swing arm. I went with perpendicular to the swing arm, but it needs to be angled back toward the rear axle at least 10 degrees to clear the frame tube (see photo). Back to cutting and grinding! Revision B coming up in a few weeks...