Honda-SOHC

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CB250/350K Shop Manual tells you to test reground valves by putting fresh engine oil in combustion chambers and pressuring ports up to 2 bar and look for bubbles in the oil. I always just looked for a continuous full grey line on the faces. But tried the pressure test on 500/4 head and four of freshly re-ground valves bubbled very slightly so after much effort got them all bubble free. Seen pro test rigs using vacuum but not positive pressure testing.  Any thoughts? Even though pressure is acting against the valve seats tending to open them, it seems a reasonable test to me. The vacuum one looks a bit iffy..as how do you know its leaking slightly....they have a pump and vacuum gauge which gives a % sealing figure. Anyway, I know my valves are totally sealed now as zero bubbles.   

https://www.dropbox.com/s/8i51vjqqdvllazj/CB350ShopManual.pdf?dl=0

Miles 42K, F: 1015252 E: 1013045 UK Spec.


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Hi There,
Let me introduce myself . My name is Jo and recently was given a rusting hulk of a motorcycle model CB750K7 to restore , which has resided in a colleagues garden for more years than are good for it. I am coming back to motorcycling having taken my bike test on a CG125 in the 1990’s and always wished to own a CB750 as my dad , bless him, had one in the  very early 1970’s.
We moved to the UK from just outside of Tokyo in 1971 when my dad took up a post at the Linwood car plant. Going  to need your help guys on a mammoth restoration!

Sayonara ..Jo