KZ900 Cylinder to KZ1000 Cylinder Upgrade Questions...

Hey all,

In speaking with Larry Cavanaugh he brought some insight to some things I just didn't think of... The man's a genius I tell ya... LOL! Thanks Larry!

Here's the situation and questions:
1976 KZ900-A4 Cylinder piston stock 66mm (with broken fins)

Without boring/honing the cases, 1015cc kit is about it. I would still have to get the fins welded up = additional $$$.

As Larry pointed out, why not just upgrade to a KZ1000 cylinder with no broken fins... Now possible up to 1075cc!
DOH, why now didn't I think of that! :blink:

Questions:
In upgrading to 1000 cylinder, will I still be required to bore/hone cases?

In researching head OEM part numbers, they don't match so will I need to upgrade to a kz1000 head as well?

Will Stock 26mm carbs mount or need to upgrade?
NOTE: Due to $$$ (& wifey) at this point in time, plan is to upgrade to 34mm smoothies later on but engine first.

What other issues do I need to think about?
i.e. increased engine height to frame...

Sorry to be a pain in the ass but a whole slew of new ideas has come to mind and as some of you have already been through this part of the modification figured I might as well ask.

Thanks,

Old Man Rock

First, you will need to clean up the cases on the 900 where the 1000 cylinder liners fit. It isn't honing or boring... it is taking a drill and grinding off a little material so the cylinder will fit. If you do this job, you will have top split the cases (my opinion here) because too much junk gets down into the lower end. It isn't that big a deal to split the cases but you will need to clean ALL case gasket mating surfaces and install new case cover gaskets as the mating line between the two case halves goes right down the middle of all the covers. Your 900 cylinder head is exactly the same functionally as the 1000 and will fit right on any 1000 block. The stock 26mm carburetors will work fine although you might need to upgrade in the future if you wanted to take advantage of the increased displacement. Also keep in mind that if you stay with STOCK size 1015cc pistons, you won't have to pay someone to bore the cylinder block as you will for the 1075 pistons. This is a couple hundred bucks so it is worth thinking about. You won't be able to tell the 1075 block is in the frame. It doesn't add any height. The displacement increase is via larger diameter pistons not more stroke. The EARLY 1015cc blocks; such as a 77 occassionally fit the 900 cases without any grinding. If you use a 79/80 block, at some point, they quit cutting the little channels under the cylinder liners where you put the orange orings that go around the cylinders. These blocks seem to ALWAYS require grinding. Anyway, I have done this a few times so if you need any tips, just holler. And last, there is no 34mm smoothie. 29/33 Mikuni VM series smoothbores but no 34 I know of. This engine you are thinking about also need some cams/springs to make the project worthwhile and some VM29 smoothbores.

Thanks George...

My 40 year friend in Las Vegas (motorcyclerecyclers702@yahoo.com) has an old KZ1000 in the back. I'll find out what year and get him to measure the liners. May just get lucky and not require any grinding what so ever!

No 34mm Smoothbores... WTF am I not getting, bad terminology I used most probably the cause. Sorry about that.

MIKUNI RS Flatslide Smoothbore Carburetors
kzzone.com/carbs.html

OMR

The goal is to take the engine to 1075cc so the 1000 block is the easiest route.

The top case needs to be bored so everything is centered properly. I wouldn't advise just grinding away at the cases until the block drops in place.

Studs have to come out so it's a good time to install the HD ones. May as well go with the HD crank studs while it apart and new cam chain.

I know, the $$$ start adding up quick when you head this direction.....It's a once and done deal however. Also consider what it costs to buy just a pipe for a Busa or a ZX14 these days and the KZ still is cheap by comparison.

Done properly it will still be humming along nicely long after many of the new bikes have been trashed and forgotten.....