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Author Topic: 1982 CB750F... The resto-not  (Read 33230 times)

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #420 on: Mar 11, 2019, 14:31:03 »
Just curious, but did you check the true on that countertop?  Curious how close it is to a proper surface plate.  Most surface plates are several inches thick to accommodate flex from the surface it sits on, as well as being ground to within .0000025"
I'm curious now too - I had to take a punt on it being true as it's the only thing in my world that's even close.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline CrabsAndCylinders

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Re: 1982 CB750F... The resto-not
« Reply #421 on: Mar 11, 2019, 16:34:12 »
Do you have a straight edge that you can use to check the surfaces with now?
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Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #422 on: Mar 11, 2019, 16:48:20 »
Here's what I got -



The ruler is the straightest edged thing I've got, but I'm not 100% convinced it's perfectly straight-edged.  I can see daylight between the ruler and the granite, but barely. Maybe 0.1mm?
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline Nybz

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Re: 1982 CB750F... The resto-not
« Reply #423 on: Mar 11, 2019, 20:02:31 »
I found out the hard way on my goldwing, when I attempted to straighten the head a back and forth motion was not the way to do it, but instead a circular motion. Otherwise there is too much pressure on one side doing it back and forth.
I had to take it to a machinist to flatten it back out.

Good luck!


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1979 CB750 LTD collectors plates
1979 CB750 K current custom rebuild
1980 CB750 F in waiting...

Past bikes
1982 GL1100
1980 CB400

Offline CrabsAndCylinders

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Re: 1982 CB750F... The resto-not
« Reply #424 on: Mar 11, 2019, 21:54:40 »
a sheet of glass is supposed to be flat, can you try that, also flip your straight edge over and see if you get the same results.
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Offline irk miller

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Re: 1982 CB750F... The resto-not
« Reply #425 on: Mar 11, 2019, 22:01:24 »
a sheet of glass is supposed to be flat, can you try that, also flip your straight edge over and see if you get the same results.
Technically, float glass is the truest surface of glass, but it's not.  It's way more true than his counter, but not as true as a surface plate.  I've used thick panes of it for similar purposes in the past, but nothing like the mating surface of a head.  All glass is prone to bow and warp, so there is a range of tolerance when it comes to ASTM standard.

Offline pidjones

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Re: 1982 CB750F... The resto-not
« Reply #426 on: Mar 11, 2019, 22:14:11 »
A 12" square of 1/4" plate glass with 600 grit spray-glued on worked well on the Hunley head and block. Used Dychem to see the high spots until it showed flat. My surface block was good for seeing if a feeler would fit under. Final testing with Prusian Blue to make sure.
"Love 'em all.... Let God sort 'em out!"

Offline wozza

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Re: 1982 CB750F... The resto-not
« Reply #427 on: Mar 11, 2019, 22:30:14 »
Good old fashioned oil stone oil and figure 8's is how Ive always done it..never had an issue......

Offline doc_rot

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Re: 1982 CB750F... The resto-not
« Reply #428 on: Mar 12, 2019, 05:00:40 »
You could always have a machinist mill a little off the head to make sure its flat and get a boost in compression at the same time, seems like a no brainer to me :-X