SOHC.co.uk Forums > CB350/400
compressions
paul G:
Rosco,
Stop running the engine until you ride it or you will glaze the bores.
Engine needs to be under load for the rings to bite into the bores.
rosco:
Cheers Paul Taken on board Hope to be on road soon Ross
McCabe-Thiele (Ted):
Back in the early 1970's when I was selling the then new Audi 80 cars the manufacturers used a special "running in"oil if they supplied a factory new engine that had to be used instead of off the shelf oil - we were told it was as per when cars left the factory they had a slightly abrahsive addidative for the first 1k miles.
K2-K6:
--- Quote from: Macabethiele (Ted) on July 26, 2021, 02:06:27 PM ---Back in the early 1970's when I was selling the then new Audi 80 cars the manufacturers used a special "running in"oil if they supplied a factory new engine that had to be used instead of off the shelf oil - we were told it was as per when cars left the factory they had a slightly abrahsive addidative for the first 1k miles.
--- End quote ---
I'd offer a contrasting view to that on a technical level. Key to that being how could a global (in lubrication terms of whole system) be targeted at being abrasive to just the piston rings and bores ? I don't believe that any engineering department would advocate using anything abrasive in that situation.
The other bearings, mains, big end, camshaft etc have absolutely no need to be altered during running, and can an abrasive pass through the oil filter element ?
Accepted that a different oil fill from production was used certainly, but most likely a singular grade low cost (huge volumes) product that by definition wouldn't have to last more than 500/1000 miles before discarding.
Also there's the principle of how abrasives work. Usually by embedding in a soft carrier sub structure (think Emery cloth) which would have the cutting component pushed into the soft main bearing material and aluminium head material, to then effectively machine the rotating components.
The whole idea of a finish hone with these materials is solely to cut the piston rings to fit the bore during initial phase of running, regardless of oil quality.
Mineral vs synthetic as often projected on the wider internet is highly misleading from people lacking the knowledge to offer competent discussion.
Nurse Julie:
Graham uses Graphogen during engine builds as a cutting in compound. The Graphogen is all broken down by about the
10th total rotation of the engine. He has been using this for over 30 years with no detrimental effect at all. He only uses it on new bearing surfaces, not previously used (as in matched) surfaces. He uses bearing guard for those surfaces. When you change the oil for the 1st time, it is very black due to the Graphogen but cannot be felt when rubbing the oil between your fingers.
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