Top-End Redo
- daveo
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Re: Top-End Redo
13 Aug 2019 11:55
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.
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.

1982 KZ1100-A2
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- old_kaw
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Re: Top-End Redo
13 Aug 2019 12:14 - 13 Aug 2019 12:16
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.
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.
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1981 Kawasaki Kz1000K1
Located in the Saint Louis, Missouri Area.
Located in the Saint Louis, Missouri Area.
Last edit: 13 Aug 2019 12:16 by old_kaw.
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- Scirocco
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Re: Top-End Redo
13 Aug 2019 12:41 - 13 Aug 2019 12:55It´s easier to use a spacer under the cylinder block to lower the compressin. APE offfers spacers with different thickness.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.
If you want to run regular fuel on 10.5:1 piston you can reduce the ignition advance timing 3-5 degrees .
My 1975 Z 1 B 900 Project
www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
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Last edit: 13 Aug 2019 12:55 by Scirocco.
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Re: Top-End Redo
13 Aug 2019 13:21
For a nice mild motor I would just use the parts you already own. With fresh rings and gaskets.
Dave
Dave
Original owner 78 1000 LTD
Mr Turbo Race Kit, MTC 1075 Turbo pistons by PitStop Performance , Falicon Ultra Lite Super Crank, APE everything. Les Holt @ PDM's Billet Goodies . Frame by Chuck Kurzawa @ Logghe Chassis . Deep sump 5qt oil pan. RIP Bill Hahn
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- SWest
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Re: Top-End Redo
13 Aug 2019 14:16
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
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
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Re: Top-End Redo
17 Aug 2019 13:31SWest 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 :kiss: her goodbye.

1982 KZ1100-A2
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- old_kaw
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Re: Top-End Redo
17 Aug 2019 13:57daveo 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 :kiss: 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.

1981 Kawasaki Kz1000K1
Located in the Saint Louis, Missouri Area.
Located in the Saint Louis, Missouri Area.
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Re: Top-End Redo
17 Aug 2019 14:54 - 17 Aug 2019 14:58
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.
Last edit: 17 Aug 2019 14:58 by baldy110.
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Re: Top-End Redo
17 Aug 2019 16:35old_kaw wrote: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 :kiss: 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.
:blush: You are probably right about one thing...except the last one.
1982 KZ1100-A2
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- daveo
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Re: Top-End Redo
17 Aug 2019 16:55baldy110 wrote: 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.
I appreciate all the encouragement to move forward. Working out the details, and may just go for it.
Will the OEM two-piece head gasket work properly with the MTC 1135 piston kit, for which I believe the bore size is 74mm?
1982 KZ1100-A2
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Re: Top-End Redo
17 Aug 2019 19:13
No it won't. A head gasket will come with the piston kit.
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Re: Top-End Redo
17 Aug 2019 22:51baldy110 wrote: No it won't. A head gasket will come with the piston kit.
My KZ cylinder block has recesses for o-rings at the four corner stud holes, whereas the ZX cylinder block this MTC kit is made for does not . Considering that, will a special head gasket be required for my application?

1982 KZ1100-A2
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