Prepping a KZ650 for racing?

Hey folks, I've picked up a '77 KZ650 to race in AHRMA's vintage superbike class and I've got a few questions and am open to suggestions.

I've picked up a basketcase '85 GPz750 to use for parts. My thoughts aqre to use the forks, front brakes, and wheels.

How difficult is it to install the GPz forks in the KZ frame? Is it worth doing or should I find a set of kz forks with dual brakes and still run the GPz rims?

I picked up a complete GS1100 swingarm but found out after the fact that swingarm isn't legal to run on a KZ. So I'm going to pick up a KZ1000 swingarm for it. It seems pretty easy to mod on of them to slip into the 650 frame. If I remember correctly, it'll just need to be narrowed very slightly.

What do folks use for shocks and what length shocks to get?

Thanks for any input!

The front end will probably bolt on. You may have to alter the steering stops though. The GS1100 swingarm would have made your bike 2 1/2" longer, not exactly desirable for roadracing, so no big loss there. If you are buying new shocks you should look at Works Performance. Not cheap, but they work well and the company has plenty of experience with race shock applications for vintage bikes. I'm thinking that the shock length for RR would be 13.75+/-

83-85 GPz750 front end will bolt right in by using a steering stem conversion bearing set from All Balls. All Balls has a page that will tell you what bearing sets you need to bolt X forks onto Y frame, and all front ends that will fit, totally slick.

GPz750 aluminum swing arm can be used (if legal) by cutting off the linkage on the bottom and welding it on top as a shock mounts, and possibly using the spacer off the GPz550 pivot bolt to use the KZ650 pivot bolt in the aluminum swing arm.

Done the above to a 79 KZ650SR, plus installed the 83 GPz750 motor.

Steering bearing size list PDF:

www.ohiocaferacers.com/OCRStemSizes.pdf

You should be able to use any non-upside down forks in AHRMA. I am working towards upgrading my stock 35mm forks to 2006-2010 EX650 41mm Forks, triples, wheels and brakes. It's been proven reliable on MOMBA2 that races in AHRMA. Newer forks means more options for upgrading. Parts are all over on ebay for these years.

a modified 750 turbo swing arm would be a good choice if allowed it is a heavy duty version of the GPZ750 less flexing I have a few around.

Yeah, the GPz arm wouldn't be legal since it isn't a tubular arm like the stocker.

Thanks for the bearing info.

I do have access to a set of prepped SV forks but I've kinda decided to set up the bike closer to the spirit of the class and use the older stuff.

I'm building this bike just to have some fun with it and not worry about building it to be the most competitive. Been there done that and my bank account had been throughly abused.

hei GP, welcome to the racing gang

like someone said here, wouldnt do a swapt to a swingarm that's longer, will slow steering

On my twin shocker racer, a 72 CB500 I went pretty high at the back but the reduction in trail required shorter offset triple clamps to regain back some "feel" for the front.

It's quite easy to try different ride heights with this idea i use, jsut make different height triangles and see how bike behaves

heard the story about doing it just for fun..... beware, its a slipery slope, but guess you know that

some kz racers popped inot this thread of mine

kzrider.com/index.php?option=com_kunena&...ew&catid=2&id=349599

TG

Yeah, I've been racing since 1999 so I'm well aware of the costs involved.

I started racing with GLRRA on a GPz750, then a RZ350, took the RZ motor and put it in a TZR250 chassis in CCS, then a RC51. Sold the 51 earlier this year and decided to go do some vintage racing.

Also have done some endurance racing with CCS and Moto-ST.

I love the look of the older KZ's so I picked up the 650 to play with. I don't want to go too radical with it since I still hope to keep it streetable.

I did some of the GLRRA races at Grattan 99-01. I really liked that track/series.