Author Topic: Yosh 812 piston info  (Read 1683 times)

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Offline knowsnothing

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Yosh 812 piston info
« on: November 11, 2016, 09:55:57 AM »
Hi all, I am building an engine with some 812 yosh pistons i picked up and I have a few questions.   This probably doesn't belong here, but I figured you guys would more likely have experience with these pistons than others. 

Here is what i have




First dumb question, arrow towards exhaust correct?

The rings i have all have an "R" stamped on them and there is a shiny one, dark one, and a one piece oil ring. 

Second dumb question, "R" side up and Shiny(left) is top and dark (right) is middle? 



And finally i came across these images in an ebay sale for another 812 kit.  I think it is the same kit as the one i am using




I just got my jugs back from being bored and I measured the ring gaps.  This is what i got:

                        1                2               3               4
Top (Shiny)   0.008   0.007   0.008   0.007
Middle (dark)    0.007   0.008   0.008   0.007
Oil                  0.008   0.007   0.007   0.006


This bike is only for the street, that being said, are these gaps too loose for these pistons?


Thanks,

-Treeve
1978 CB750k Green - 811 engine
1978 CB750k Blue - for sale
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline knowsnothing

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Re: Yosh 812 piston info
« Reply #1 on: November 11, 2016, 09:56:47 AM »
Sorry, double post  >:(
1978 CB750k Green - 811 engine
1978 CB750k Blue - for sale
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline 540nova

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Re: Yosh 812 piston info
« Reply #2 on: November 11, 2016, 10:37:56 AM »
So Yoshimura expects you to run your engine for 3 HOURS, between 6000-8000 RPM?! Wow.


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Offline Retro Rocket

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Re: Yosh 812 piston info
« Reply #3 on: November 11, 2016, 04:57:43 PM »
So Yoshimura expects you to run your engine for 3 HOURS, between 6000-8000 RPM?! Wow.


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From idle to 6, then idle to 7 then 8 thousand.... that includes everything under those numbers too.... ;D
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.