building ahrma middleweight superbike--need advice

building a 1977 kz--685 cc limit
will put zx wheels and forks
looking for low buck H-P
what works ? when i go to road race i go to race not -work on it.
has kerker-4 into 1
looking to install 26 mm carbs.

What's allowed?

For starters you want racing compression ratio.

Low 70s CFM head with some nice .400 lift cams would help the situation. Stock is 59CFM.

26mm carbs are a nice jump up but they're heavy bastards.

Will it be a multi track bike or a single track bike?

If single track, what's the layout? Does it favor top end or midrange?

Lots of little considerations to think over...

There's a guy named Alex from Canada that is really on his game with those 650's. He can steer you to clutch upgrades and other nice mods. You might find him on the 650 forum. Very nice guy and very smart. Can't remember his forum name but you'll recognize his 650 in a heartbeat. Setup for drag racing, RED, mechanical injection.... Can't miss it

Allowed:
Consistent year head and cases.
685cc max (as stated) so 700cc kit is out unless you want to be the slow guy in heavyweight...
Round slide carbs (new are ok)
Exhaust can't be slip on, must be "period correct"
Otherwise I believe it's just about anything goes on the internals.

I'm hoping to make a Kz650 middleweight bike as well...shooting for the 2013 year. My local track is Road America which I'm guessing will be mostly a mid-top end power circuit. Racing cams, increased compression through milling, adjustable cam sprockets. Not sure what else can be done.

Which tracks are you local to and are you planning on doing the entire circuit?

I also forgot the Cavanaugh special...my bad. Get some flow in there.

I think the Alex that Larry is talking about goes by "injected" on this forum. You also might try and get in touch with "CoreyClough". He runs a GPZ550 in the Super Dinosaur class. Also we have an Italian member "Turboguzzi," who races a GPZ 750. All three of them have experience racing the smaller Kawasaki air-cooled fours. Please make a build thread if you have time. I'll watch.

track bike--grattan-gingerman--mid-ohio

Cool. I think Gingerman is the only other track I could reasonably make it to.

Personally, I think porting/VM26/VM28 or Keihin CR29's and some race cams are going to get you the most out of the engine. I think there is still a lack of a manufacturer for adjustable cam sprockets so you would have to pay someone to make them custom for you, but would be money well spent.

1 of the most important things i have found about going fast at the track is corner speed. there are more corners than straights, so u stand to shorten your lap times if u can focus on going faster around a corner that a straight.
u will find it much more gratifiing to pass someone in the corners than on the straight, there will be many more passing opertunities in the corners as well.
If your budget is tight think of suspension before motor.
when u put 17" modern wheels on u loose a lot of ride height. Then u add modern forks and u can loose more.
My advice is to search deeply, and only add parts that will maintain ride height.
17” wheels may be a trade off since u can get more choices of rubber. Check with the racers and find out what kind of rubber they use and if u can get it in taller sizes.
Find the longest , newer forks u can, again, check with the guys that know.
Good luck

I have really been wanting to go racing again.. its been years.. Im not really wanting to do the highend modern sport bike again, too expensive and lets face it, im rusty.

I wondered if modern suspension and wheels on a vintage bike was legal.. this thread seems to suggest yes that is the case, am i mistaken?

:side: Think I speak for KZR when I say

" In no way are any of these modifications legal or implied to be and no one wants to be responsible"
:woohoo: :silly:
Any who what is Legal

as soon as you chop cut rebuild you are deamed non dot but that goes for alot exaust handle bars and just about anything we bolt on our kzs the book reads any non stock parts or so I was told.

The guy to ask about road racing with the 650 motor and chassis is Steve Darlington...
I believe he is a member here, if not here is his contact info:

www.teamkz.ca/
teamkz@rogers.com

He was using stock bore with increased compression by milling head and barrel.
The stock 650 head can be opened up pretty good even with stock valve sizes... you want to keep
combustion chamber small and cranking compression between 200-220 psi (you can still kick start at
that level if rules allow)
He mentioned to me that .400" cams may be too much for the intended application with the stock bore - maybe a .360-.370" cam is ideal with 74-78 CFM port work.
It seems that all the 650 cam sprockets I have come across are hard and cannot be slotted with a round file... you need a carbide bit to slot them.
Use stock clutch pack and upgrade to a needle bearing pusher... shim the stock springs with some .030" steel washers.
VM28 carbs are a good bet since they are period correct and are basically a bolt on.
Vent the crank case and cam cover... 3 places is ideal.
Dyna S will run quite a while total loss on a 8 AH battery - check the rules and what local track guys use
He was not running exotic fork/wheels/shocks

painterjohn wrote: I have really been wanting to go racing again.. its been years.. Im not really wanting to do the highend modern sport bike again, too expensive and lets face it, im rusty.

I wondered if modern suspension and wheels on a vintage bike was legal.. this thread seems to suggest yes that is the case, am i mistaken?

It depends on the series you race in. For AHRMA I believe it has to be a period correct swing-arm (round tube for a KZ, although this has been debated elsewhere) but can be braced using similar material, there is a limit on the size of the forks, more modern wheels are allowed but with a specific restriction on the number of "spokes" on the mags.

Brakes calipers have to stay single piston, I believe, also.

The rule book is on the AHRMA site and lists all of this pretty clearly.