Z2 750 crank (Bossie the Kaw)

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15 Sep 2015 09:25 #690168 by missionkz
Replied by missionkz on topic Z2 750 crank (Bossie the Kaw)
Are you cracking and replacing the crank and rods???

Bruce
1977 KZ1000A1
2016 Triumph T120 Bonneville
Far North East Metro Denver Colorado

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15 Sep 2015 10:48 #690190 by SWest
Replied by SWest on topic Z2 750 crank (Bossie the Kaw)
No, just switching pistons. It's been a nagging question for a year now. Had some lunch and a short nap. Time to finish tearing it down and some pics.
Steve

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15 Sep 2015 13:55 - 15 Sep 2015 14:01 #690209 by SWest
Replied by SWest on topic Z2 750 crank (Bossie the Kaw)
DAMAGE; I've been saying the manual adjusters are dangerous. Here's why.




I got it too tight and destroyed the center rubber roller and the front guide. As the chain became noisy, I kept adjusting it. Good thing I bought some extra parts and decided to do this. :dry:


The 903 block is in front. The 903 gasket worked just fine.


Here's the deck height.






2,5mm below the deck.




Home made tool for removing pistons.




Talking the head inside for cleaning and honeing the cylinders.
Had a broken ring on #4 piston. No damage.
Steve
Last edit: 15 Sep 2015 14:01 by SWest.

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15 Sep 2015 15:23 #690226 by missionkz
Replied by missionkz on topic Z2 750 crank (Bossie the Kaw)
Yikes!! Did you find any of the rubber and dampening material junk in the oil or stuck in the pickup screen. I did, many years ago, in my 77' KZ1000. It had crap in the oil that I found was material worn off the wheel and front slider guide!! I was forced to do the same as you and I've never used a manual chain tensioner.

Bruce
1977 KZ1000A1
2016 Triumph T120 Bonneville
Far North East Metro Denver Colorado

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15 Sep 2015 15:38 - 15 Sep 2015 15:39 #690231 by SWest
Replied by SWest on topic Z2 750 crank (Bossie the Kaw)
I still have my spring loaded tensioner. I'm tempted to put it back on. If my chain had broken, it would have made for one FK'ED UP DAY. :ohmy: It's ironic I was warning about them and here is the perfect example.
You can see the number 45 stamped on the crank. Before I button it up I'll measure the rods. 2.5mm is a lot. No wonder I had low compression. If I lose cc's, so FKing what. That would mean it IS a 750 crank and should spin faster as planned. I'll take more pics tomorrow.
Steve
Last edit: 15 Sep 2015 15:39 by SWest.

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15 Sep 2015 16:20 #690244 by kawi810
Replied by kawi810 on topic Z2 750 crank (Bossie the Kaw)
i was right you had a low compresion POS

original owner of a 1984 gpz 750
1985 turbo 750 stock, being restored.
1984 gpz 750 with 810 cc wiesco's megacycle cams(471-10) 34 mm flatslides v&h pipe ported head dyna ignition. bottom end, crank case from turbo 750 and sprockets.

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15 Sep 2015 17:08 #690247 by SWest

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16 Sep 2015 01:13 - 16 Sep 2015 01:20 #690281 by kawi810
Replied by kawi810 on topic Z2 750 crank (Bossie the Kaw)
looks like you need a valve job i would send it out and have new viton seals put in .one of the cylinders looks pretty scored up time for a rebore.take some more pics so we can see how bad the cylinder is do you have a dial bore gauge to measure the tapper ? and take a valve out so we can see how bad the seats are.

original owner of a 1984 gpz 750
1985 turbo 750 stock, being restored.
1984 gpz 750 with 810 cc wiesco's megacycle cams(471-10) 34 mm flatslides v&h pipe ported head dyna ignition. bottom end, crank case from turbo 750 and sprockets.
Last edit: 16 Sep 2015 01:20 by kawi810.

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16 Sep 2015 03:21 - 16 Sep 2015 15:35 #690289 by SWest
Replied by SWest on topic Z2 750 crank (Bossie the Kaw)
I have no interest in YOUR opinion or anything you can dig out of a book. :lol: Valves done last year. For everyone else.
Kibblewhite valve springs, new valve guide seals, new Dorimi valves. More pics to come. B)
kzrider.com/forum/2-engine/596420-valves#653678
Steve
















Last edit: 16 Sep 2015 15:35 by SWest.

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16 Sep 2015 04:49 #690300 by SWest
Replied by SWest on topic Z2 750 crank (Bossie the Kaw)
Bruce, you're right. I'll need to drop the pan and clean out all the junk on the strainer. When I did my oil change a small piece of plastic came out. It was from the cam chain sprocket. 40 years old so I wasn't alarmed, now I am'. Everything is cleaned up and I will put it back together today. Still have to take pics of the rings and if they migrated or not :whistle: , more of the crank, the hone job, etc. There always has to be a snag and I was prepared for it. B)
Steve

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16 Sep 2015 09:07 #690319 by SWest
Replied by SWest on topic Z2 750 crank (Bossie the Kaw)
I took some pics of the rings. They migrated quite a bit. Not close to where they were set.






Head cleaned up, painted and ready to go.


Some pics of the crank and rods. The only place you can see where it was welded is the center pin. I'll also jot down the markings on the rods. You can barely see them.










Steve

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16 Sep 2015 09:18 #690321 by Tyrell Corp
Replied by Tyrell Corp on topic Z2 750 crank (Bossie the Kaw)
Interesting looking below the rings where the oil has been burning, and how it differs slightly between pistons. Looks to me like they were past their best.

I'm thinking now the most critical thing for good ring seating is the cross hatch hone, I have a honing tool taht I've used in the past but In future I'll leave it to a pro..

1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces

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