Kz900: Stock Bore - High Compression Pistons

That would be interesting to see. I could see that if the VM26 hit a critical flow or a restriction point prior to the head's intake port. The information that I found on Larry's site about the stock KZ900 cylinder head flow, didn't flow that much to begin with. I am sure once you begin by having the head ported, then they may become an issue. Will keep my eyes open for a set.

Cory

Actually 1015 in a 900 sleeve is a very popular and reliable mod We have done hundreds of them. Got three in here right now to do.

Jay,

I should give you a shout once I get into this engien a little further to discuss what type of build or some recommendations on combos.

Cory

Funny this topic came up now, I currently having a similar email discussion with Larry C. I'll be turning 50k miles in the next year sometime and figure by then I'll have all the brake, chassis, and suspension upgrades done and time to move to the engine.

I'm not looking for anything serious, just a nice refresher for my daily driver KZ900.

He suggests a 1015 MTC or Wiseco 10.25:1 piston kit, combined with either Web 118, Web 931, or Cam Motion Z2 cams (all shim on top, drop in), keep my Kerker, and a set of 29mm smoothbores. Of course, a thought-out port job would tie everything together nicely.

Interested to see what you come up with!

It all depends on what my pocketbook will allow. From my build, should have the chassis, brakes, electrical, bling, etc... working nicely. The engine really appears to be in excellent shape for having 60K + miles on it. Again, trying to justify. High compression, with a stock bore, get some drop in cams (Andrew 2x's), keep my exhaust, and then figure out what I want to do with the carbs. My other idea, go through the thing quickly, new studs, nuts, gaskets, timing set, valve seals & springs, lap the valves in and salp it back together.

Cory

Americanclassix.com sells a 998cc Z1/KZ900 piston set that looks very much like the new Yosh Z1 998cc piston set I have. Part # is PS694

Here it is:

APE Jay wrote: Actually 1015 in a 900 sleeve is a very popular and reliable mod We have done hundreds of them. Got three in here right now to do.

Try running one in nebraska on a hot summer day,same affect as running an 1105 with stock 1000 sleeves around here. :woohoo:

If you didn't want to bore, you could find a decent set of 1015 jugs for not too much.

APE Jay wrote: Actually 1015 in a 900 sleeve is a very popular and reliable mod We have done hundreds of them. Got three in here right now to do.

:woohoo:

Les I have a question for you as you seem very knowledgable on these kz's. Checking valve clearances is it better or more accurate to check the clearance 180 degrees opposite peak lobe hight or about 45 degrees after the valve comes back in its upward rotation? Some say check at opposite position from deepest position. What is your take on this. I am running 6 thousanths and 4 thousanths exhaust and intake. Figure it is better to hear them than smell them.

To chime in here, I am running 900 cylinders and block with 1015 bore kit with J.E. pistons and 10 1/4 to one compression with excellent results. The compression woke it up tremendiously. I also am running 28 mikuni vm ss carbs, open header, pods and stock cams. I did degree the cams though and am making 105 horsepower. The lobe center works best at 108 on this bike. I am actually running a tight piston to wall gap 2 and a half thousanths. I have to raddle at all. (Mike)P.S. Scott Barger of S&K racing did my boring and ring gapping. Great job.

Just for my own piece of mind I go with the valve nose pointing away from the bucket but I really don't think it's that critical. As for the spec I go off the manufacturer's specs and shoot for the upper of it in case they aren't able to get back in to check in a reasonable time. That 105 HP is stout for that combo! Great job!

I looked at the pistons saturday and they are at least 12:00-1's but didn't have the size on the box. I'll be back there by wednesday at the latest and will take micrometers to measure.

Les