Frame bracing and rear swingarm reinforcement on 1978 KZ650B

I am reading all I can here on forums, digesting as much info as I can.
I will be going through frame up restoration, frame will be powder-coated.

Initially I didn't think about making changes, but reading here I am considering it especially that I do want to tinker/weld
Another question is rear swing arm. I read somewhere that those were weak from a factory prompting aftermarket versions. So, I was wondering if it was a DIY to maybe reinforce that somehow as well "while in there"

If you have any pointers, pictures, drawings, I will appreciate it.

This thread has lots of good info (the 650 and 750 frames are very similar.)

www.kzrider.com/forum/11-projects/610573...a-81-kz750-e?start=0

Where did you read the KZ650 rear swingarm is weak? Maybe you read about the KZ900 rather than the KZ650? Keep in mind that the KZ650 beat all the AMA / FIM 750cc records with the stock swingarm . Only the original shocks (which were not very good) were changed. I've owned my 1977 KZ650-C1 since it was new and never found the swingarm to be a problem at all. Ed

650ed wrote: Where did you read the rear swingarm is weak? Maybe you read about the KZ900 rather than the KZ650? Keep in mind that the KZ650 beat all the AMA / FIM 750cc records with the stock swingarm . Only the original shocks (which were not very good) were changed. I've owned my 1977 KZ650-C1 since it was new and never found the swingarm to be a problem at all. Ed

Info on other forums, somewhere. Maybe it was about other KZs but it's more like modern rumor about that "era" KZs
Thats why I am asking here OK, swingarm is good (also it's different on B from C). What about frame, do you think it needs anything? I am definitely not a racer, just normal riding.

Posted separate topic on shocks, so hopefully will get right pointers there on suspension setup.

I've put more than 61,000 miles on my 1977 KZ650-C1 and highly recommend the following:

First, the KZ650 original rear shocks were toast after about 10,000 (or less) miles. If your bike has original shocks replace them with quality units. I have been using Hagon shocks for more than 13 years and they still work like new. Prior to those I used S&W shocks which also worked great but did not look similar to stock units.

Second, be sure to buy quality tires. I use Pirelli Sport Demons and they work extremely well. I'm on my 3rd set; they last about 7,000 miles per set.

One other thing - take some time and perform ALL the maintenance listed in the Kawasaki Service Manual. At that point you will have eliminated many small but important issues that may have been neglected. Things like fork oil, brake fluid, etc. can help make a bike perform great or poorly, and if those things have been neglected (and assume they have been) the bike will not perform nearly as well as it should and won't be much fun to ride. The Kawasaki Service Manual has a chart of all the maintenance items and describes how to perform them. Also, assuming your bike has all the original parts, such as airbox, exhaust system, etc., keep those parts on it! The KZ650 was engineered by true professionals and has everything it needs for highly spirited, or even mature, street riding. Also, forget making any changes to the swingarm, frame, forks, etc. especially for street riding! Unlike some earlier KZ models, such as the KZ900, the frame, swingarm, forks, etc. are easily more than sufficient for highly spirited street ringing. These bikes are engineered extremely well.

Below is a picture of my 1977 KZ650-C1. Ed

I agree with Ed in that the Kawasaki engineers got the chassis design right with the 650. The steering head area of the frame is nicely reinforced with stamped metal gussets and is significantly more braced than the 900 and 1000 frames in that area. Upgrading the shocks, steering head bearings, and maybe the fork springs would be good places for a few bucks during your rebuild.

katit wrote: I am definitely not a racer, just normal riding..

I think you answered your own question. Even normal riding a Z1 you dont need any bracing. Its not like the frames are made of foam rubber.

Every time I see a pic of Ed's bike it reminds me I need one of those in my life.

650ed wrote: First, the KZ650 original rear shocks were toast after about 10,000 (or less) miles. If your bike has original shocks replace them with quality units. I have been using Hagon shocks for more than 13 years and they still work like new. Prior to those I used S&W shocks which also worked great but did not look similar to stock units.

Ed, is this what you have on a bike?
www.hagon-shocks.co.uk/catalog/partdetai...rderdetailid=1529834

I don't see any for sale in USA. What other brands available/good? I would like to stick with "stock" look

What is your suggestion for front? Just new springs? I assume I need to change anyways for my weight. Which brand would you recommend? Progressive springs?

I am little confused because "Progressive" make only one spring. Other makers produce different ratios and provide calculators I can use to figure out for my weight

That looks like the shocks I have. Regarding the front forks - mine still have the original stock springs and they work just fine for me. They worked well years ago when I weighed 165 pounds and they still work fine now that I weigh about 210 pounds. You can measure the spring length to be sure they are still in spec. The correct spring length is 494.5mm with a service limit of 485mm. Be sure to flush and change the fork oil, and to use the correct amount (measure 396mm from the top of the forks with the springs in and the front wheel off the ground) and be sure to pump the forks several times before measuring to expel and air that may be lurking there. I use BelRay 15w fork oil, and I only do one side at a time to eliminate the possibility of the forks collapsing all the way down. Ed

For shocks you could also consider Ikon. They are reportedly clones of the old Koni shocks that were popular back in the day.

www.ikonsuspensionusa.com/search/

If you want increased performance from your forks there is Race-tech. I got springs and valve emulators. Really improved the front end for me. got rid of the brake dive big time.