TOPIC:

Can anyone tell me the differences between a 1977 spec 1000cc and the later 79-80 units aside from the ignition?? heads, valve sizes, cam specs, and finally hp #'s. I'm trying to find the best base motor for a project bike. thanks

Z1 - 903 cc - 82bhp @ 8500rpm - 8.5:1 copression ratio- 36 and 30mm valves - 4 mikuni VM 28mm carbs - DOHC - 9 piece pressed together roller bearing crankshaft - lighter 'pork chop'-style counterweight.

'77 - '78 KZ1000-1015 cc-83bhp @ 8000rpm-same valves & camshaft timing as Z1 - 8.7:1 copression ratio - VM 26 carbs - same crankshaft as Z1, but 3kg (6.6lb) were added to flywheel, this smoothed out engine but made it more reluctant to rev freely.

'78 Z1R - engine was largely the same as KZ1000A2 except 4>1 exhaust and a return to VM28SS carbs of the Z1 - 90bhp @ 8000rpm.

'79 KZ1000A3 or Mk II - 1015 cc - 93bhp @ 8000rpm - crankshft flywheels were still full circle, but the crankpin diameter was enlarged to 31mm (from 29mm) - Mikuni 28mm Carbs with accelerator pump - electronic Ignition.

'80 KZ1000 - Fuel injection - 96bhp @ 8000rpm.

'81 KZ1000J,K,M, amd P - 998 cc - valves 37mm inlet and 32mm exhaust - crackshaft still a pressed up item but with Z1-style lighter 'pork chop' flywheel - Mikuni BS34 constant vacuum carbs - 102bhp @ 8500rpm.

thank you for your detailed info. I appreciate your time.

No problem. The info in the book I have didn't get into heads at all, and barely mentioned the valve sizes. But as you can see, HP increased with each new engine.

Just one little correction
The 81-82 KZ1000K (LTD) and KZ1000M (CSR) only have 92 hp vs the 102 hp KZ1000J.

I think it was carbs and cams that made the difference.

is it possible to fit a J model head with the larger valves and carbs along with a upgraded electronic ignition on my lower block and obtain 102bhp with my 77A1? I'm aware of the compatability amoung the Z-KZ series models but I don't know what actually works well with what. I'm kinka looking for a recipe for a nice 120rwhp and if I can obtain a strong base motor comprised of this head and those carbs and so on then the rest is just $$$ lightened crank, valve job, mild porting, +1mm or so on valves should obtain 120-135rwhp easily. anyone have a Muzzy twin plug head laying around?? right 2 on the shelf!

Cylinder head.. J model head has larger valves and ports. This head can be used on earlier style cylinder and lower end by installing APE #CCIA cam chain sprocket adapter in head . How to tell which head you have.. Early style heads have four factory drilled and tapped 6mm holes in the center to bolt in cam chain idler gear. Z1 900 heads have 6 mm exhaust studs, KZ1000 8 mm. On the J model head, the four cam plugs at the ends of the camshaft areas are bolted in, on the early style head, they just push in and the valve cover holds them in. The J model / '81-'82 GPZ1100 cylinder head has a larger combustion chamber than the early style head. When these heads are used on the early style motor, a compression ratio drop of about 2 full points can be expected.

www.aperaceparts.com/tech/techkz1000.html

So, unless you are going to put a turbo on it, you would have to replace the pistons.

Is there a big difference in power and gearing on a Kz 1000 LTD versus a KZ 750LTD ?

Just read through the APE site and found the explaination for alot of my questions...looks like you can use stock rods and pistons but to retain compression you have to mill the heads as you loose 2 pts going with the J head. I'm sure they have a nice fix with a piston or rod kit to cure that too. Anyone here have hard dyno #s with a KZ1000 fitted with a J model head with a 1075cc kit with 410 cams??

900 and 1000 cranks use differant counterweights,1980 kz1000 had 28mm carbs with accelerator pumps,1980 z1 classic was the fuel injected motor.the biggest differance between 77&79,80 was electronic,ignition,bigger carbs,possibly better exhuast.79,80 had a better crank ,but it doesnt really matter till you get above 160-170hp,the 77 also has a nicer loking head in my opinion

the j-motor head has much larger combustion chambers ,which are fine if you have high compression pistons otherwise youll have deck thehead the j-motor heads also have problems with the valve seats "rocking' unless you can pin them in some how.id reccomend using your 77 head and doing the porting and valve job on it.hope this helps,happy wrenching

What we do a lot with people who want to put a big bore in their KZ and also a J head is we use the J big bore pistons.

They have the pin hole about 1 mm lower because the J has a shorter rod. We use a 1 mm spacer under the block. This arrangement takes care of the compression loss with the J head.

Jay
www.kzzone.com