TOPIC: Top-End Redo

Not sure if this is a smart question or not, but here it is regardless...

In the long run, how much better to install a cylinder block with new sleeves, versus honing the old ones when the bores are worn but still within spec?

Ideally, there should be no out of round or taper in the bores, and the piston to wall clearance would be to the low end of the spec. Personally, if I were rebuilding an engine and longevity was the goal I'd try to find some OEM OS pistons and then have a good company like APE do the cylinder boring/honing work.

I re-did one of my Z1B's. The cylinders had been bored to 1015 cc but I wanted to go back to 903. I had two choices...new sleeves or used cylinders. I went with used cylinders that were within spec and only required honing because it was a cheaper alternative. I only put a couple of thousand miles on each of my bikes each year so the used cylinders will last my lifetime.

We're really talking only about the 80+/- mm length of cylinder surface where the rings travel, correct?
Short video explains basically what is going on in there:

A cylinder sleeve got the most wear on the TDC and BDC area. The piston rings residence time is much longer( slow piston speed) in this area.

Cylinders do not wear evenly over time. The high cylinder pressures near the top, combined with large temperature variations over the entire cylinder, ESPECIALLY on air cooled cylinders, make the bore wear far away from round and true. Honing ONLY does not return these out of round bores to round. A good Sunnen type hone will do ok, but there is flex and stone pressure changes that do not allow it to re true the bore to round. Add to this the point that the piston to cylinder clearance will now be far greater than the specs call for. The ONLY way to return the bores to round is a machine type boring bar, or mill with boring head, but the boring bar is better, and then hone. That then requires the cylinder to be increased to the next oversize.

daveo wrote: We're really talking only about the 80+/- mm length of cylinder surface where the rings travel, correct?
Short video explains basically what is going on in there:

Sorry but only 66mm stoke on these engines.

I'd think about APE too..... pretty sure they have a Wiesco 1170 set with 10 and a 1/4 to 1. With your carbs bet that thing would be a real beast.

zed1015 wrote:

daveo wrote: We're really talking only about the 80+/- mm length of cylinder surface where the rings travel, correct?
Short video explains basically what is going on in there:

Sorry but only 66mm stoke on these engines.

I thought the distance between the top and bottom piston ring would be added to the stroke to determine the total ring movement (wear area) in the cylinder.
If I am mistaken, oh well...it's not my first or last.

KZB2 650 wrote: I'd think about APE too..... pretty sure they have a Wiesco 1170 set with 10 and a 1/4 to 1. With your carbs bet that thing would be a real beast.

With lower compression the engine runs well on Regular gas. It operates cool and should last a long time. I may bump the compression up a little, but prefer to keep it close to stock. Would be the third top-end redo since I've owned her, and I hesitate to add more stress than she might be able to handle.

True. A lot of folks believe raising the compression ratio will give them lots more horsepower, but that really isn't the case unless other engine modes are performed. The links below show the effect on hp as compression ratios are increased. Ed

www.wallaceracing.com/hp-cr-chg.php
www.bgsoflex.com/crchange.html

650ed wrote: True. A lot of folks believe raising the compression ratio will give them lots more horsepower, but that really isn't the case unless other engine modes are performed. The links below show the effect on hp as compression ratios are increased. Ed

www.wallaceracing.com/hp-cr-chg.php
www.bgsoflex.com/crchange.html

Thanks for posting that great piece of information!

Requesting fellow-member suggestions before deciding on which direction to go.

I have the cylinder block from prior to my last top-end change in 2015 packed away in a box. I may reuse it with a new set of Kaw Std rings on the pistons I modified for the ZN1100 head and ZX1100 camshafts, which BTW have worked beautifully together.
This would be my least-cost approach that would yield no performance gain except a decrease in oil consumption, which I would welcome and be satisfied with.
Besides that, a cool running motor that loves regular octane gasoline doesn't bother me either.

However, another option has been teasing me for a while now...

There is an MTC 1135cc 10.5:1 piston kit available for the ZX1100 engine, except with 17mm piston pins to fit 82 KZ1100 rods.
Not sure whether increased compression is desirable, since it may require running high octane fuel vs. regular, and likely cause the engine to run hot and stress the bottom-end which has not been touched since the engine was built in Japan 80K + miles ago.
I received advice that having 1mm additional material removed from each piston crown during the manufacturing process would lower the compression ratio by some amount, and yield approximately 155lb. cranking compression pressure. This sounds reasonable to me, but I am no engine expert. I wonder what the new compression ratio would be, and whether it would enable regular gas use.

All opinions and suggestions welcome.

Daveo said "Requesting fellow-member suggestions before deciding on which direction to go."


Wellllllll... IMHO, the more you turn up the wick on that beauty, the more attention it will need. There is a very recent thread of spending wads of money, looking to do the "ultimate" overhaul... is now once again in pieces with 2 scored pistons out of the "kit".. Although I know we all love to tear down our motors over and over again, option #1 will likely run the longest, and be trouble-free... Just my $.02.

daveo wrote:
I received advice that having 1mm additional material removed from each piston crown during the manufacturing process would lower the compression ratio by some amount, and yield approximately 155lb. cranking compression pressure. This sounds reasonable to me, but I am no engine expert. I wonder what the new compression ratio would be, and whether it would enable regular gas use.

It´s easier to use a spacer under the cylinder block to lower the compressin. APE offfers spacers with different thickness.
If you want to run regular fuel on 10.5:1 piston you can reduce the ignition advance timing 3-5 degrees .

For a nice mild motor I would just use the parts you already own. With fresh rings and gaskets.
Dave

I have 10.25/1 pistons and use regular gas. No problems. If you have 8.5 pistons the new ones would complement your other mods. If 1135 is the max I'd try and keep it to 1100 or so. If money's tight new rings would be the way to go.
Steve

SWest wrote: I have 10.25/1 pistons and use regular gas. No problems. If you have 8.5 pistons the new ones would complement your other mods. If 1135 is the max I'd try and keep it to 1100 or so. If money's tight new rings would be the way to go.
Steve

My old cylinder block is out of spec to re-ring my pistons, so the 1135 MTC kit is the-choice to keep this old girl up and running.

Decisions, decisions...perhaps it's time to her goodbye.

daveo wrote: My old cylinder block is out of spec to re-ring my pistons, so the 1135 MTC kit is the-choice to keep this old girl up and running.

Decisions, decisions...perhaps it's time to her goodbye.

You KNOW that it will drive you even >more< CrAzY if you get rid of that beauty. I know it's your therapy too, and you would just have to buy another project. SOON.

What happened to the old block you had stashed? Just a resizing and oversize pistons / rings will fix the oil consumption.

I must have lucked out. My bike only leaks oil (slightly LF O-ring) but does not smoke or burn oil, not even a little bit.

No matter what you decide, I know you will do a great job of fixing it.

Bumping up the compression to 10.25-1 is not going to stress the bottom end at all. It won't create excess heat either. Get the 1135 MTC kit you wont be sorry and there is no downside to it. The problem arrises when you bump compression a lot then add big cams, porting, bigger carbs, ect.. That will lead to excessive heat and stress but the bottom end of these engines are pretty stout. The engine Old Kaw is referring to was damaged by operator error and had nothing to do with the piston kit he installed Your over thinking this Daveo.