As the P series uses the same pivot bolt and bearings as the J/KM series, I reckon the swingarm should bolt in just fine. There are different swingarm part numbers for the police bikes. The C series has a different number than the P1 and it has a different number from the rest of the P series (P2 and newer). I suspect they are minor differences, but do not know for sure. If the P arms are braced in some way, they will also be heavier, which may not be great for racing. If you want stronger and lighter, a Suzuki GS 1000/1100 aluminum arm would be a better choice. You will need a small spacer on each side and will need to use Shocks for a GS. There are also aftermarket aluminum arms, but they can get pretty pricy. If strength and weight are your priorities, a custom arm from one of the members here would be the best combination of strength, weight, coolness and price.
Click on the PDM button below to contact him.

Dr. Gamma wrote: Wait to you measure the clearance between the frame boss and the swing arm bolt!!!!!!! Then the clearance between the inner swing arm sleeve and the swing arm bolt!!!! One of the very first things I noticed on '79 factory Kawasaki Superbikes was a very non-stock looking swing arm bolt and nut. When I put the swing arm bolt through my Kz1000 frame I quickly saw why they used something besides stock parts. There was like .035 thousands or more of play between the two. Same with the inner sleeve too!!!!!

I just noticed that the police model has a different swing arm, it looks beefier and is braced more at the pivot. Will this fit on a KZ1000J/GPZ frame and or other KZ frames?

Wait to you measure the clearance between the frame boss and the swing arm bolt!!!!!!! Then the clearance between the inner swing arm sleeve and the swing arm bolt!!!! One of the very first things I noticed on '79 factory Kawasaki Superbikes was a very non-stock looking swing arm bolt and nut. When I put the swing arm bolt through my Kz1000 frame I quickly saw why they used something besides stock parts. There was like .035 thousands or more of play between the two. Same with the inner sleeve too!!!!!

I then had my favorite machine shop make me up a few oversize swing arm bolts. They also made me a tool that kept both sides of the frame in alignment as I hand reamed the frame bosses to size of the new oversize swing arm bolts!!! I have to lightly tap the new swing arm bolt into place on my Superbike frame. My machine shop then honed the inner swing arm sleeve to have only .001 thousands clearance between both. In the end I now had a swing arm and frame that had zero play between the two!!!! Just imagine if you have like .035 thousands side to side at the swing arm pivot point. How much side to side movement would you have at the rear axle!!!!! Same thing applies to the play in the motor mount bolts on the Kz1000 frames. If you run ream fit oversize bolts, the motor now becomes part of the frame.

I used to eyeball the factory Superbikes and check out all the things they did to their bikes. I would photograph everything on those bikes from end to end. Sometimes the factory guys got a little annoyed at me hanging around and taking so many photos!! The Honda guys were the worse in trying to get in the way of me taking some closeup photos. I got many of my ideas from just checking out the factory bikes. Why copy the bikes that run in like 10th place or so. You check out how the winning bikes did things!!!!

Back in the day, installing an aluminum swingarm from a Suzuki GS 1000 / 1100 was popular. It is a very straight forward swap. Usually just a washer or two on each side where the pivot bolt goes through, and installation of shocks with a clevis rather than eye on the bottom.

There are new aluminum arms available if you don't mind the price.

I use a Pitbull rear swingarm stand for my RZ500. Works great.
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You can move the shock mounts to raise the back end and I suspect they cut or put shorter springs in the front end. Is the frame raked? Pics of the steering head would help.
Steve

You are welcome anytime Lakshan. And appreciate your compliment on my 650. We have the same year, so hopefully we can exchange some ideas as you progress through your new bike.

One other item that may have been covered but worth mentioning again; Did you get the Owners Manual with your bike? And, you may want to get a Service Manual on this specific model. They are out there. If you need one I will check to see if I have a spare.

One item I did not mention would be:
Suspension - The front fork fluid likely needs replacing. There are various weights/thickness of fork oil. There is likely a thread around here somewhere or post your questions here. My bike was prone to tank slapping at high speed before the fork springs were replace with stiffer Race Tech units for my weight. The rear shocks were barely adequate for the day when new. I replaced mine with a pair of Works Performance and love them. The stock rear shocks made the bike weave and even wag when running fast in sweeping curves. The new shocks eliminated this. It is now on rails when up to speed. What I am saying some of the first upgrades worth doing are for the chassis. BTW, I worked with the Works Performance engineer to make the correct length shock for the 1977 KZ650. It's swing arm is a different length than later models. The result were shocks that truly fit the bike. If you order be sure to let them know they have produced another.

As you can see, there are a lot to items to consider for something that appears quite simple. Best advise is get it refreshed and think about what you might want to do with your bike. You can customize from there and make it yours.

z1kzonly wrote: You should have plenty of resources over in the UK.
Find a custom, fab, cool (TV show style) shop to help you out.
Dime City, Legends, Ace. Even ask The Harley Guys! Business is money.

Go with the GS 1100, Or GSXR your cheapest alternatives. I have a picture with dimensions in inches of a GS 1100 Suzuki swinger here.
Give you the basic idea size.

Thank you for posting this image, it does answers most of my questions.

While waiting for the frame to get back I scrounged up a 1982 Suzuki GS1100E swingarm. Cleaned it up and found out the finish was in really bad shape so I sent it to the powder coaters for an aluminum finish.

You Need new swing arm brass bearings!!! (upgrade to needle bearings). What bike do you talk about?