Need Some Cylinder Head Advice

Hey KZr'ers. Could use some input on my 1977 650 engine mods. I'm going with the Wiseco 810 kit which will involve new 750/4 jugs that will be bored out. I've located a couple of 750/4 motors to choose from, an '81 and an '82. I've checked out the archives and learned that with the 750 head on the 650 block there will probably be an issue with my cam chain if I use the 750's cams and sprockets.

I also learned from another site that some guys have used the 650 base, 750 jugs but retained the stock 650 cylinder head.
I have already put a lot of work and $$$ into my current factory 650 head (ported, polished and triple angle valve job) and am not overly excited about having to swap out the factory cam chain. I am of the belief that the bottom end of these motors are bulletproof and don't want to touch the southern part of the motor or split the case to install a new cam chain if I don't have to. The motor only has 14000 miles on it.

So anybody have any opinions on retaining the 650 head and cams on the 750 jugs and 650 bottom end? I know the 750 has a little hotter cam and slightly bigger valves but by machining the head 0.020" and properly degreeing the cams I figure this will make up for the extra power the 750 head will provide.

Cheers-Colin Firth -Ontario Canada

If you have a 650 head that has been properly ported (and maybe even install the 750 valves) then I'd use it, You can still use the 750 cams (and I would) just by swapping the sprockets. How are you going to enlarge the bores in the case to accept the larger 750 liner without splitting the case?
IIRC, there used to be a woman around St. Louis that had pretty much the same setup and was running in the 10 sec range.

does the 650 use a pressed crank like 900-1000?

wireguy wrote:

does the 650 use a pressed crank like 900-1000?

No.

i was just wondering becuase he didnt want to tear down the bottem end

Thanks Steell for your input. If my memory serves me correctly, the cases only need to be enlarged by around 1mm in diameter. I'll have to check into it further before turning a wrench. Given this minor die grinder job it might be feasible to make this enlargement while the motor is still in the chassis according to a machinist friend of mine who has lots of experience doing this sort of work.

He said that he could fab up a small tray that would fit into the top of the crankcase. This tray would have magnet or light coating of oil in the bottom of it to catch the metal shavings before they fell onto the crank journals or the oil pan. This process would save a ton of work as the motor wouldn't have to be removed from the frame and the case would not have to be split according to the machinist. Clever idea if it will work.

I like the idea of simply swapping sprockets on the cams and upgrading to the 750's hotter shafts and valves. I will have to have larger seats pressed in if I go this route and obviously a new set of seals. Hopefully the stock 650 guides will be a ble to handle the bigger 750 valve faces.

I will probably upgrade my clutch springs (new Barnett Clutch last summer) to handle the extra power. I just picked up some Mikuni 34's that I will rebuild and properly jet according to wiredgeorge's suggestion as well as a Dyna electronic ignition and Dyna coils from the KZr classified section (I love this site!!!)

Any other suggestions are appreciated and any guesses on what kinda power this combo might deliver with the mods? The bike came stock around 64-66 hp. It already flies with the Wiseco 700 kit I put in last spring and along with the 14 tooth drive sprocket (down from the stock 16) it is pretty quick outta the hole...but there is always room for improvement-right?

Cheers-Colin Firth - Ontario Canada

Post edited by: reborn650, at: 2005/12/21 22:21

I have an 84 KZ700, what did they use for cams and valves, I know it revs quicker than the 650 I have. I just put this engine on my 78 650SR but haven't rode it yet so don't know what to expect seems like a lot more power but maybe the 650 was tired

The 650 and 750 use a one piece plain bearing crank, unlike the roller bearing crank in a 900/1000.

Magnets in the bottom to catch the shavings won't work real well since the case is made of aluminum

It would be a whole lot simpler to just split the cases and then bore the holes larger, a lot more accurate than using a hand held die grinder also, remember, you are going to have to work around the rods if you don't split the case.

I don't know anything about the 700, but I would expect it to be pretty much the same as the 750, including the cams. You could compare part numbers on buykawasaki.com and see if they are the same.

Thanks Steell for your input. I spoke to my machinist buddy today and he indicated that the magnets in the tray would be to hold the tray in place on the crank journals. The light coat of oil in the tray would be to help catch the shaving according to him. Another riding buddy said that maybe simply stuffing an oil soaked rag into the cases would catch any filings as the die grinder trims the 1mm of metal.

I would prefer not to have to remove the motor from the frame if possible. I went through this last winter on the restoration. I understand that it will be tricky working around the rods but they can be pulled outta the way as I work my way around the cases. Obviously having the cases machined would be the best but I'll burn that bridge when I get there.

I have tracked down the contact # for a guy who races a '77650 up here in Canada in the vintage club. I think he has done some of the same mods that I am looking to do. Apparently he has had tremendous reliability and makes a ton of power with the old 650 base, KZ750 heads and cams. I will also explore swapping sprockets from my 650 cams onto the 750 cams to eliminate having to change the cam chain set up. When we disassembled my 650 motor last spring to install the 700 Wiseco kit, my bike mechanic friend (he has 2 Kz's he drags) was surprised at the excellent condition of my cam chain assembly, shafts and sprockets. Hopefully they didn't take too much of a beating last summer.

On the GPz site there is also a detailled outline of the changes needed to make this combo work.

gpzrider.lagemann.org/technical/FAQ2000.htm

I'll talk to racer up here and then decide how best to proceed before I order the Wiseco 810 kit in early January....maybe there will be some better deals then.

Cheers-Colin Firth-Ontario-Canada

Post edited by: reborn650, at: 2005/12/22 13:47

Are you refering to Steve Darlington? If so, he is a member here also (as well as the GPz mailing list).

Yup Steell. I spoke to Steve by phone today and he gave me some good advice from his own experience racing Kz's in the vintage bike events.

Steve and I were chatting about the Kzr site and he said that if it wasn't for places like this (and the Internet) a lot of old classic bikes would be junked, but instead they are being kept alive through exchanging ideas and parts. I have to agree with him. Tons of thanks to all of the Kzr faithful for keeping the legendary Kz rides alive and well.
Cheers and Merry Christmas to everyone.

Colin Firth -Ontario-Canada