Worlds Biggest KZ650?

Been reading so much good info from you guys on the 781cc, 810cc, 831cc and 880cc kits here and would like to share this.

In the June 83 cycle world (service section) they tell of a 650 built by Whitney Blakeslee (the man responsiable for the kz650 based superbikes) with Champion Kawasaki 1980 Harbor Blvd in Costa Mesa, Ca. There still there looks like to me only on a diff street. From there map within a block away.

It used a 73mm bore KZ1000 pistons and a stroke of 60mm for a total of 1021cc and possessed the realiability that might be expected of such a grossly enlarged motor.

More luck was had by using oversize 71mm kz1000 pistons with a stock stroke for 855cc. They state that the piston crowns had to be exextensivly reworked, the rod ends needed to be enlarged to match the kz1000s larger pin size and larger liners had to be installed. For years I dreamed of this until I saw the 831cc kit by MTC.

They then state Blakeslee suggested a more reasonable street machine could be made buy installing larger liners and one mm over kz750 pistons (for 761cc)although (he states) the piston crowns may need to be reworked.

Cycle World then states that a 750 block might be a better idea for the 761 piston and the addition alum around the liners would be beneficial for a big bore motor.

Think I'll stick with the 810 kit myself but thought you guys might enjoy reading this. Must of been a screamer though.

Lorcan has a 903cc billet block(I think) made for a 750 (turbo, but easily swapped to a regular 750 or 650) Stock stroke I believe, Im not sure if it was ever built or not, I just remember Steell mentioning it awhile back. I think it uses gpz1100 sleeves?....
an update would be awesome!
Scott

What's the CR of the 810 kit?

10.25-1 with a 750 head, and I think around 10.8-1 with a 650 head

77KZ650 wrote:

10.25-1 with a 750 head, and I think around 10.8-1 with a 650 head

I still think the ideal solution is a GPz70 head with .030" cut off the mating surface, that provides 10.8-11:1 compression along with the larger ports and valves.

And it only takes a few minutes with a Dremel to elongate the cam sprocket mounting bolt holes.

steell wrote:

I still think the ideal solution is a GPz70 head with .030" cut off the mating surface, that provides 10.8-11:1 compression along with the larger ports and valves.

And it only takes a few minutes with a Dremel to elongate the cam sprocket mounting bolt holes.

Ahh yes, the ol' GPz70.

Post edited by: caffcruiser, at: 2006/12/08 21:58

Hey - KZB2 650 I put an 810 in my '77Kz650 last year and the bike is much quicker than I expected.

I picked up 1980 Kz750/4 cylinders and bored them out for the Wiseco 810 pistons. I put in Kz750 cams, Gpz750 intake valves, kept the 650 exhaust valves, milled the head around 8 thou to clean it up and ported and polished the 650 head.

It is reasonable to expect that Wiseco put a lot of effort into their 810 design which includes pistons, rings, wrist pins, circlips and a head gasket. Lets face it, Wiseco knows their pistons. I would stick with a proven set up that is basicallly a bolt-on with minor modifications instead of playing around with an untested formula unless you have lots of money and pistons to burn.

Cheers-Colin Firth-Ontario Canada
1977Kz650/810 with lottsa go-fast goodies tucked away inside.

Will the GPz750 head bolt right up to a KZ650 jug/bottom end setup?

How much better is the flow? Bigger valves? Interested.... hmmm....

Hey caffcruiser. Interesting question. I don't think this has been raised here before.

Here are my thoughts on this swap. The answer would depend on what year the 650 is. If it is a 76-79 no, because of the cam chain set up and mountings in the 750's head casting for the cam chain assembly. But if the 650 motor is from 1980 onward it should fit as the 650 changed to a similar cam chain set up as the Gpz used. You will probably need to use a 750 head gasket.

The head should bolt on but if I am not mistaken the bolt holes on the front center and back center of the 750 head (hidden underneath the camshafts) are larger than the bolts that fit into the top of the 650 stocker's jugs. On my 650 head to 750 jugs I had to open up the bolt holes on the 650 for the 750 bolts to fit through. This might cause a problem if you use the 650 bolts with the 750 head as these two bolts might not seat properly in the head's bigger bolt opening. Bottom line is that you will probably need to enlarge the bolt hole openings in the 650 jugs to accept the 750's bolts.

You also have to make sure that the cam chain, adjusters and sprockets from the 650 motor will be compatible with the Gpz head and camshaft sprockets.

The benefit of using the Gpz head would be better high rpm power and breathing due to slightly bigger ports, larger valves and slightly bigger combustion chambers. The downside is that with the Gpz exhaust cam you cannot use the stock tach drive as the Gpz exhaust cam doesn't have the tach drive gear machined into the cam.

Here is an interesting site that deals with upgrades to the Gpz 750.

members.tripod.com/gpz_rider/technical/FAQ2000.htm

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2006/12/08 22:38

Lots info there!

Here are my thoughts on this swap. The answer would depend on what year the 650 is. If it is a 76-79 no, because of the cam chain set up and mountings in the 750's head casting for the cam chain assembly. But if the 650 motor is from 1980 onward it should fit as the 650 changed to a similar cam chain set up as the Gpz used. You will probably need to use a 750 head gasket.

The motor is a 79 KZ650. The cams I am planning to run are the GPZ750A standard cams. I've already swapped over the KZ650 cam gears onto them to prepare for the event.

The head should bolt on but if I am not mistaken the bolt holes on the front center and back center of the 750 head (hidden underneath the camshafts) are larger than the bolts that fit into the top of the 650 stocker's jugs. On my 650 head to 750 jugs I had to open up the bolt holes on the 650 for the 750 bolts to fit through. This might cause a problem if you use the 650 bolts with the 750 head as these two bolts might not seat properly in the head's bigger bolt opening. Bottom line is that you will probably need to enlarge the bolt hole openings in the 650 jugs to accept the 750's bolts.

I asked about KZ650 jugs for the benefit of the people running them. I'm running KZ750 jugs, and was planning on ordering a set of the studs from APE. I don't mind doing a little boring work at all though.

You also have to make sure that the cam chain, adjusters and sprockets from the 650 motor will be compatible with the Gpz head and camshaft sprockets.

See above. Running GPz cams with KZ650 cam gears. (Also planning on running a manual cam tensioner from APE)

The benefit of using the Gpz head would be better high rpm power and breathing due to slightly bigger ports, larger valves and slightly bigger combustion chambers. The downside is that with the Gpz exhaust cam you cannot use the stock tach drive as the Gpz exhaust cam doesn't have the tach drive gear machined into the cam.

Running my new Electrosport Acewell digital speedo/tach, which reads from a coiled wire around the spark plug wire, so the tach drive is irrelevant in my situation.

So basically, the cams are the main benefit, followed by the bigger valves and bigger Com.Cham.? Hmm... decisions decisions. Would it be easier to mod up a GPZ head to fit my setup, or to mod a KZ head with the valves from a GPz and port the hell out of it? :evil: :lol: And on top of that, would it be more reliable/powerful to use the GPz head over the KZ head given those comparisons? I dunno.... :side:

Post edited by: caffcruiser, at: 2006/12/08 23:06

Hey caffcruiser - Sorry for the war and peace info, thought I would give you all of the scenarios my Friday night brain could come up with. You hadn't listed your bike specs so I tried to cover all the bases. Gotta say that I like the handling upgrades you mentioned in your other post. Now you've got me thinking about what I could do to tweak the handling while keeping the stock look.

Cheers-Colin Firth-Ontario Canada

Yes Reborn I agree on the 810 kit. Mainly just thought you guys would like hearing of other combos. Great to know questions can be asked about it when the time comes and I can count on the answers.

Your thought on the 750 head sounds very wize to steell gotta add to the top end.

77kz650 seems like your always there to help with a answer to so with all the help here I'm feeling more and more like breaking down and spending the cash.

Will be taking my time though.