I did the conversion on my '88 kz1000p. That's the same frame as the '90.
You have to cut the board frame mounts off of you bike. No way around that. So once you're in you're in.
I approached this problem by first making sure I could figure out the brake pedal. I figured the foot shift lever was a no brainer but I did need to make a few mods to that lever because of my foot peg choice.
For the brake I bought a 1983 Kawasaki KZ1000 brake pedal shaft and brake pedal off ebay. The brake pedal shaft fits perfect into the '88 kz1000p frame and aligns without modification to the rear master cylinder, brake light switch and return spring without modification. Well maybe a little hand sheet metal bending. When I put the break pedal on the shaft the foot pad was just where I wanted it. Luck really. So what I thought was going to be the hardest part was in fact the easiest.
I then bought an '83 kz1100 ltd shift foot lever because it was the cheapest lever I could find. This was advantageous because I needed to move the foot pad back an inch and a half so I wasn't shifting with my big toe nail. The shape of the 83 ltd shift lever made this relocation a simple proposition. If I would have used different foot pegs, relocating the foot pad on the shift lever may not have been necessary. To move it back I simply cut cast one off, drilled a #7 hole, tapped it for a quarter inch bolt. bought a grade 8 quarter inch bolt with an appropriately long un-threaded length, and used fuel line for the rubber grip pad.
For the foot pegs I used '84 kawasaki GPZ550 front foot pegs. Why? Again they were the cheapest. Why spend cash if they might not work? They looked pretty nasty but spray paint does wonders. To get them on the bike I found that there was one threaded bushing below the swing are bolt on both sides of the frame that I could use for mounting. I then had to make some brackets to hold the foot pegs. Ultimately I made the brackets out of half inch steel plate. I bought 18 inches of 2 X 0.5 inch steal plate for the entire job. That came to $24. Why steel? Because it was cheaper than aluminium and easier to grind and file. My machine shop consists of a small harbor freight drill press, grinder, hack saw, and file. I could have done the drilling with a hand drill if I didn't have the drill press, but a drill press is a plus.
Before making the brackets out of steel, I mocked them up out of wood. That allowed me to make sure they fit as good as possible while working with an easy to work with material. I knew I was going to have to drill a second hole through the frame on both sides of the bike and the wood mock ups made locating that hole easy. You need to shim the pegs on both sides out from the frame. I shimmed mine out 0.5 inch on the left (shifter) side and 1.0 on the right side (brake). Good thing I bought 0.5 inch thick steal plate. After completing the wood mock up I used the wood parts as templates for the steel parts.
Were the '84 kawasaki GPZ550 front foot pegs the right choice. Well they were a bit complicated to fit because of the mounting points, and the construction required them to be located to the rear by about an inch further back than I wanted. That is why I had to cut the shift lever back. Cutting the shift lever back means I need more lever foot pressure but it is not excessive, and I get a nice positive snap of the lever. If I had to do it again I wold likely try a different peg, but I'm happy with the results overall.
Now for some pictures. Sorry, my photography skills suck.
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