Honda-SOHC
Other Stuff => Misc / Open => Topic started by: AshimotoK0 on October 07, 2020, 08:25:11 AM
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My S90 engine is unstamped apart from 'S90-' and one half is sandcast and the other half is diecast :) .
The sandcast half is internally coated with some kind of brown resin, presubably to protect against any porosity.
When you sancast chaps clean your cases, how do you prevent damage to that coating or doesn't the 750 have it?
I would imagine chemical dipping would be a no-no unless some sort of replacement coating was re-applied. Epoxy resin perhaps?
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These people may be able to answer as those motors were routinely coated as I understand, may tell you what they are using currently.
https://www.mv-agusta.co.uk/
Interesting business anyway with fabulous engineering.
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Don't know if this helps but on the US SOHC forum lots of people seem to coat the inside of the casings with a product called Glyptal for sealing porous aluminium castings. Haven't seen it mentioned on this forum though.
Charlie
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The CB750 sandcast has a coating on some but, not all. I strip that coating off and have never recoated it with no known problems. I not even sure if it is a sealing coating or a coat that they used at the foundry to stop the sand sticking to it. I have never found this coat on a sump pan where most of the oil sits.
I have done a test on a sandcast sump pan by half filling it with oil and put it in the oven for a hour. Didn't find any oil staining on the outside of the pan ;)
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We used to paint the insides of our Compressor Crankcases back in the 80's.......AFAIR we used International Paints Yacht Paint. At the time I thought it was to seal the inside of the case and to stop any 'sand' getting into the oil. The Compressors were BIG buggers that a bloke could stand inside and they were cast iron.
The Crankcases on the smaller Compressors were ALL 'fettled' meticulously and the 'Fettlers' were very proud of their skills and experience in making sure any and all loose bits/ sand were removed. We also had a huge Degreasing machine where Tricoethylene was the prime cleaning agent, and I was pally with a Painter who was known as a "Dawber' (it was an American Company) who told me 'in the past' he had had to apply filler along all the welded seams on the Air Receivers (Tanks) before painting them to make the welds look tidier !
Our Turbo Compressors Driven by a RR Avon Engine) had Lube Oil and Seal Oil Tanks (the Seal Oil was for the seals around the Compressor Shaft) and these were built into the skids which the Compressor and all their ancilliary kit was mounted on. We lost a lot of sleep over welding slag in these tanks and the lads who had to climb inside and work in confined spaces deserved a lot of praise. We didn't lose many Compressors due to their seals being buggered up on Test, but if we did, it meant a couple of days to strip the seals out and replace them and it put our Test Department under a lot of pressure as they suddenly had to work 24/7 to get their programme back on track. It was a great place to work as many of the blokes were Time Served Toolmakers or Machinists (mostly from the Altrincham area) and there was only one way to do things there - the right way !
I wouldn't be surprised at Honda Sandcast Engines having a sealing coating applied......as Honda wouldn't want any 'bits' buggering up the oilways of their biggest ever Project back in 1968/9 would they !