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Why are our pistons so tall? 20 Dec 2009 06:45 #339953

  • otakar
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les holt wrote:

You are right, I apoligize for drifting off topic, I hope I didn't offend you otakar. I contemplated long before posting, I try to conduct myself in a better manner believing I am a representation of my family and their values. I try to post each time as though my mother would be reading it.
Again, I apoligize for off topic and belittling of anyone.


On the contrary. You are one of the very few who stayed ON Topic. I just wish more people would. I am agreeing with you. I by no means am offended, because there is no cause to be. I posted that to bring the thread BACK TO THE TOPIC. ;)
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000

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Last edit: by otakar.

Why are our pistons so tall? 20 Dec 2009 08:37 #339978

  • KZQ
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Hi Folks,

I deleted and edited this thread from 108 to 80 posts. It took that much to get rid of the Asparagus fights. This is a good thread please do your best to leave the Asparagus' zipped up.

Back to your regularly scheduled, slightly drifted, topic.

KZCSI
www.KZ1300.com
Riders:
1968 BSA 441 Shooting Star, 1970 BSA 650 Lightning, 1974 W3, 1976 KZ900, 1979 KZ750 Twin, 1979 KZ750 Twin Trike, 1981 KZ1300, 1982 KZ1100 Spectre, 2000 Valkyrie, 2009 Yamaha Roadliner S. 1983 GL 1100
Projects:
1985 ZN1300

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Why are our pistons so tall? 20 Dec 2009 10:42 #339997

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KZCSI wrote:

Hi Folks,

I deleted and edited this thread from 108 to 80 posts. It took that much to get rid of the Asparagus fights. This is a good thread please do your best to leave the Asparagus' zipped up.

Back to your regularly scheduled, slightly drifted, topic.

KZCSI


"Slightly Drifted" Boy you have a flare for the understatement. :laugh:
It is really worth to read the Wikipedia page to explain this subject quite well.
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000

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Why are our pistons so tall? 20 Dec 2009 12:33 #340015

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This thread sounds more like a old vs. new thread. The modern bikes have great performance, and as to whether they are reliable or not, I don't know. I do know that I don't like them. They feel uncomfortable to me any way. I don't like they way they look. If I ever did get a modern bike it would be an overpriced Harley. At least those bikes maintain their overpriced value over time.

IMO, the 70s / early 80s KZ bikes just have better styling to them. I really doubt in 30 years we are going to see people trying to restore these modern jap bikes. But we all have different tastes, so just buy whatever makes you happy I guess.
1983 KZ750 N2 Shaft

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Why are our pistons so tall? 20 Dec 2009 13:47 #340026

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Why are our pistons so tall? :ohmy: :unsure: :blush:

Because it is long stroke technology unlike today with short stroke (over-square) technology, where pistons MUST be short to fit............
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000

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Last edit: by otakar.

Why are our pistons so tall? 20 Dec 2009 14:35 #340031

  • TexasKZ
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Actually, the real issue here is oil. Those antique long-skirt pistons require recycled automotive oil, ususally 10w-12. The newer short skirt pistons require full synthetic motorcycle specific oil, preferably a 5w-75. Unless of course you use a Fram filter. :P
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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Why are our pistons so tall? 20 Dec 2009 16:01 #340045

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Personally, I use pure Goose Grease. The slickest stuff known to man. :laugh: :woohoo: But I was told that the KY brand is just as good. Very low friction, for extended life. :laugh:
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000

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Why are our pistons so tall? 20 Dec 2009 17:44 #340060

  • 9am53
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otakar wrote:

Personally, I use pure Goose Grease. The slickest stuff known to man. :laugh: :woohoo: But I was told that the KY brand is just as good. Very low friction, for extended life. :laugh:



mmmmmmmmmm, goose grease on fresh, out of the oven rye bread.....

or better yet:

mmm chleba ze sadlem

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Why are our pistons so tall? 20 Dec 2009 19:09 #340083

  • unomike
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Good Grief ... What a thread! I guess its old technology vs. new when it comes to pistons and other motor parts. Some good, some bad. As I see it and I'm not going to step on toes here ... It boils down to the rider keeping his or her motorcycle within it's design limits and not abusing it by stunting. New or old, a bike will last as long as its owner provides the proper maintenence and rides it responsibily. Of course an high-performance engine will wear quicker than one built for endurance but still when you boil it all down, those are the keys to keeping a bike alive for years.
Own: 1980 Kaw KZ1300,Stage 1 kit,K&N pods
1972 Harley Davidson XHL Sportster, 1972 Suzuki T500, 1974 Hodaka 125 Dirt Squirt, 1980 Honda 250 VTR, 1983 Yamaha 750 seca and a 1974 yamaha GT80 for my son.
Bristol, Tennessee. USA

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Why are our pistons so tall? 28 Dec 2009 09:45 #340957

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9am53 wrote:

otakar wrote:

Personally, I use pure Goose Grease. The slickest stuff known to man. :laugh: :woohoo: But I was told that the KY brand is just as good. Very low friction, for extended life. :laugh:



mmmmmmmmmm, goose grease on fresh, out of the oven rye bread.....

or better yet:

mmm chleba ze sadlem


Boy, I can hear my arteries hardening already. And requiring an annual angioplasty. Don't be putting any ideas into my head that will shorten my riding life. :angry: :woohoo: :laugh: :laugh: :laugh:
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000

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Last edit: by otakar.

Why are our pistons so tall? 28 Dec 2009 16:16 #340986

  • DrWhizBang
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That wikipedia article is good. So allow me to ask an additional question on the subject that may stir things up again ;-)

"An undersquare engine usually has a lower redline than an oversquare one, but it generates more low-end torque."

Would the corollary of this be that if I bore out my 650 engine to 810, I am necessarily raising the redline? And to get further off track, how would I calculate that?
KZ650C2 w/810CC in Saint John, NB
-- a sleeper, methinks.

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Why are our pistons so tall? 28 Dec 2009 18:03 #340994

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Theoretically that would be correct. But due to the fact that you would also have to accordingly reduce the reciprocating mass to complete the equation, the red-line would stay the same in your case. To raise tour red-line you would also have to change other things, such as your valve train, and reduce the mass of your crank shaft and the mass of the pistons. This is what the whole question is all about; Why are our pistons so tall? But saying that. yes there is a relatively simple formula in figuring how much your red line is going up. Take the existing piston sweep area (existing bore size area) and figure the percentage you are enlarging it. The red line should go up about the same percentage +/- about 19%. Now you must be sure that your other components can handle it also. Such as the lower and upper rod bearings. You almost definitely have to go with larger wrist pins to get more pin surface area to reduce stress and you might have to do likewise to the main journal area. This is how Kawasaki did it with the GPz1100 by making the wrist pin larger, there fore being able to spread the load more. You will also be limited by the period metallurgy of the engine.
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000

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Last edit: by otakar.
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