Kz650 best head

Hello everyone

I am rebuilding a kz650b1 trying to give it the best performance and reliability i can with small budget and some spare time

My plan is:

K700 wiseco kit
Cvk keihin carbs off a zr7
Stock airbox with k&n filter element
4into1 headers off a zr7 with short aftermarket muffler
Dyna s ignition
Kz750 cams

My doubt is now which head to use

A ported kz650 head or a stock kz750 or even a ported kz750 one?

Thanks everyone

From my notes:

VALVE SIZES
My 650 Head Intake 33.0mm Exhaust 27.8mm
My 750 Head Intake 34.2mm Exhaust 30.0mm

My 650 and 750 Cams
My stock Z650 cams 0.303” lift
My KZ750 cams 0.320” lift

Thanks a lot

This is very useful

I was also wondering because i have read here in other posts that somehow a kz650 could be a better choice because smaller intake and exhaust ports and valves means faster flow of mixture and gas

Since i need a new (used) head i can chose the one i will decide will fit my case better.

In the list of options there is also the zr7 head which should fit and it is for sure the cheapest way out there

I believe your engine uses a roller cam chain, whereas the 750 engines use link plate type chain. Be sure whatever head you select will be compatible with the chain roller system parts. Also realize that the later year 750 engines moved to an electronic tach and a bathtub shaped combustion chamber too so better check piston clearance.

Good luck

By vict182: I am rebuilding a kz650b1 trying to give it the best performance and reliability i can with small budget and some spare time

Do you already have any of that stuff & have you added up the cost?
A rough guestimate from your list, it's going to be quite a bit.

In my opinion rebuilding with a big budget would be to go for 29 smoothbores or some flat slide carbs, yoshi cams, kerker exhaust, to have the head ported by some racing workshop, and so forth.

Wiseco kit was cheaper than 4 sets of stock rings, if i could take the same pistons and bore. 400usd

Zr7 carb and exhaust was still the cheaper route compared to other ones, getting some modern patterns which are a good upgrade i think. A rack of rebuilt 24 (with a 700cc displacement?) 26 or 28 mikunis were a more expensive route, getting less results. Same about exhaust. 100usd for the cvk carbs and 100usd for the exhaust.

Dyna ignition is worth the peace of mind of getting rid of points and condensers thing. 150usd.

50usd for the kz750 cams

My calculator says 800usd.

Now which head? A kz650 or kz750 is about 200usd
A zr7 100usd

A nos kz650 or kz750 about 500usd. Which would be the expensive route again i think.

I am just wondering which head will take the best out of this setup

The roller chain is no problem, i will use the kz650 sprockets on the kz750 cams.

The kz750 and the zr7 head have the mounting holes for the central sprocket in the middle of the two camshafts.

No problem losing the rpm drive as i will use a digital one

My doubt is just about performance

The answer could be even that there is not much difference so i should go for the best deal i will find between those different options. But i would like to know opinions based on someone's experiences

Thanks

vict182 wrote:
Wiseco kit was cheaper than 4 sets of stock rings, if i could take the same pistons and bore. 400usd

OEM 750 rings are about $52/piston, so $208 for a full set.

And don't forget that with Wiseco pistons you have to pay for a bore job which can easily cost $200 extra.

Ok but i would need to buy 750 pistons and cylinders, and have them honed too at least. How much does it cost? Pointless anyway.

I already collected all the parts i listed
Except the head
So any other consideration about past decisions will be very appreciated for the next engine i will rebuild if it will ever happen.
I do apologize for saying "low budget"

Still wondering which would be the best head for this setup, and why

Thanks

Lotta little stuff adds up........ Dyna with coils, plugs and wires is closer to 275............ Liska cam chain roller and large rubber wheel just over a hundred.....kept the stock center 2 rollers and main center roller and cam chain, I had the guides replaced (Ape), Ape springs, perf grind, surfaced, closer to 500 without porting but will admit could be done cheaper, (stock 650 head) , I put in heli coils in all the cam caps more $ but of course could get get away without ......

Forget the crap gasket sets out there and went nos on base gasket, oil pan, clutch cover, valve cover, o rings, rubber dampers, oil pump screen, tack seal and o rings etc, seals are around 45 a set, nos clutch plates and springs, oil, filters, sealer, loctite, shims, jets, good Golan fuel filter, line, gaskets, o rings and possible valves for carbs, new carb holders, a few special tools, clutch hub holder, ring grinder, inch lb wrench, float level gauge...... rings in by hand no cost.

My starter clutch went to hell a year after I was done and had to tear the pan off and clutch out again for that (sprocket, hub and rollers, lock nut thrust washer etc at least 150 (rollers, springs and pins with nut etc can be done for half that without the sprocket and hub but I only wanted to do it once)....

Then you start with another new chain, sprockets, tires, brakes, suspension and its like damn..... I figured that too low.

Sure I'm for getting a few things too........ don't get me wrong it sounds like you know what your doing and what you want just be sure to add for the many small things that took me by surprise........ Can't help you much on the head will be looking for advice here...... and the stock 750 1980 cams are closer to .335 lift and .342 (forget which is ex and intake) with 10 degrees more duration over stock 650s. Ecelon has it in one of his first posts.

Just a couple of things to consider:

1. zr-7 heads use very specific cams that can only be used in zr-7 heads and kz750 cams CANNOT be used in zr-7 heads.
Kawasaki changed the thrust bearing design for the cams and made the zr-7 cams so they cannot be exchanged or substituted. The zr-7 cams are the same lift as the kz750 anyway.
The cam chain tensioner is a totally different design and shape than the earlier kz650/750 because the cam gudes are totally different.
So if the kz650 roller guides are not interchangeable, then you may be out of luck.
Also the upper cam cam chain guide mounting holes are not exact to the kz650 roller mounting holes. You will need to elongate/modify the mounting holes on the kz roller in order to get it to attach properly.
So if you buy a zr-7 head, buy it complete with the cams, carb intakes (you have to have these to use with cvk carbs) and the zr-7 valve cover.

2. zr-7 carbs are identical in design to the 1985-1997 zx600a/b/c ninja cvk32's (also cheaper) but the jetting is different. The zr-7 carbs use two different emulsion tubes for the needle jet on 1&4 and 2&3. And the needles are notoriously to lean straight from the factory. But all of that will be moot as you are pairing them on a possible 650 or 700 or 750cc pistons and/or with 650 or 750 head so you will have to invent jetting to make them work.
If you already bought the zr-7 carbs, then you need to make the valve size and displacement as close to the zr-7 to make them even close jetting wise.

Just food for thought.

maybe a slight threadjack will reveal some more possible combinations for the op...I have 79 kz650sr with 710 Wiseco's (10:1?), Megacycle cams(125-70 I think?) and valve springs, stock head cleaned up by ACI Engineering, Dyna S ignition with Accel coils, It rips. Hard...at full throttle anyway. I can't get throttle position from just off idle to about 1/4 throttle to run worth anything. I am trying to use VM28ss carbs with accelerator pump disabled and several different sets of pods because I don't think the stock airbox will fit the vm28ss's. I have been trying to tune these for months. Is there a different needle/needle jet combination that I can use? Or should I just settle for the vm24's and airbox from a 650B1? Will the vm24's be a cork on this awsome motor?