Kz650 '76 Historic Race Bike

Hello all
I get a lot of value from this forum, ideas and such, so I thought I'd post up my bike. I bought this as a 12 years in the shed non runner. Most of the work I've done myself, except for the rebore and engine internals. A lot has been done on the cheap!

I race in a historic class, "Period 5 Formula 750" Our class is very gentlemanly, but fast and competitive also. We are not allowed mods that were not available after December 1982, so have to be careful about modifications we make.

My main goal was to lighten her (over 30kgs, 65lbs), she had to be quickish, but due to the nature of my class more importantly reliable.
A short list of changes: 700cc Wiseco kit, GS1100E swingarm, dual discs, racetech emulators and springs, a lot of small things.

Future changes? I have a KZ750 head and cams on the way. Hopefully it will be a worthwhile change, with no piston clearance issues. I'd also like some Keihin CR29s if the future budget permits. Perhaps rearsets, but I have long legs and they are already in the way

That is very nice and am hoping you put up some of your tuning tips that you've found to work and how that 750 head and cams works out too.

What a beauty. Thanks for sharing.

Very nice looking bike there, both on and off track. Are you allowed to add an oil cooler? If you haven't already, can you change the stock drive chain to a 520 to save some weight? The rear sets would allow for more ground clearance in the corners, if that is what is scraping.

Yes I have an oil cooler, and the new (GPz I think) pan has the take off there. Fitting have to be "the high pressure type" so a few hoops to jump through. End of the season I'll pull the engine and do some frame bracing and painting. I'll do it then I think.

Mainly I'd like to know the (in the post) KZ750E head and cams will bolt on and clear the 700cc 64mm Wiseco pistons, from what I read I think they will fit ok.... There is stacks of room for improvement power wise, the guy who ran the dyno tells me he thinks the flattening out at the top of the power curve is a limitation of the carbs. He's pretty sure CR29s will add a fair bit.

At the moment VM24ss carbs, 15 pilots, 4th clip, 120 mains, velocity stacks inside foam Ramair filters. It runs well and pulls strong, especially past half throttle.

If you can run an oil cooler, the ZR550/750 Zephyr is larger than the GPz. You'd be amazed at the oil temp when racing. Either way, have fun!

Cams really woke my GPz550(615) engine up(66 hp and 39 torque). Can you run aftermarket cams?

I put in the 750E cam .330 lift vs .304 and I think 10 deg more duration but need to double check that. Seems like it gave me another 4-500 rs at the top end. Can you go to the gpz cam and be legal I've read the 83-85 has 365 lift and I think another 10 deg duration. Has a diff base circle though that needs to be worked out and does away with the mech tack and needs a electronic. Can't help you on the head but like you seems like I've read you can.

I'm working on 29mm smooth bores right now (mainly o rings and a cleaning) to put back on and plan on Dynoing mine too so will compare ( maybe with both carb set ups but not sure on that)...... could be a good month away though. Good to see your jetting too. I'm richer (and could very well be to rich also) at 17.5s, clip in the 5th slot and then a touch leaner at 117.5 mains w/ ape pods..... I've been told the same about the carbs lately about the 24s running outta gas above 7,000 w/ the 700 kit and small cams by 3 or 4 guys that know there stuff.

Yes I can run aftermarket cams Corey, but I'll have to run with what I've got for now.

I'm surprised I didn't have to jet up the midrange, and it's still a touch rich there, a mystery for me. I was also surprised at the 120 mains, bigger than I would have gone. The dyno tells all

From my notes:
CAM LIFT
Z650 Intake 0.304” (7.722mm)
Z650 Exhaust 0.304” (7.722mm)
Z750 Intake 0.342” (8.687mm)
Z750 Exhaust 0.335” (8.509mm)

That's nice to see...... .342/.335 lift sure sounds better than my figure of .330. Like that front fender....... I take it its fiberglass and could you tell me what it came off of and do you have any idea of the weight savings ?? Thanks.

On your dyno run are you running the 750 cams or still the stock 650cams and head etc?

Just curious as I am trying to get a ballpark jet setting for my stock 650 that is getting VM24 carbs and 750 cams.

The dyno run is with the stock cams and head. I'm guessing it wouldn't make any difference to jetting, but am glad to be corrected if someone has done it...

The front mudguard is an 83 GPZ750 item, which needed a little heating, bending and fiddling to make it fit, I left the factory brace off for an alloy one.
From my notes: minus 1.6 kg : 2kg metal to 400gm plastic mudguard