Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: adespin on January 23, 2020, 04:42:43 PM
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Found this article while browsing, a bit worrying if you own a sandcast.
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=22&cad=rja&uact=8&ved=2ahUKEwjL3uqTj5rnAhUWRBUIHa5ACVw4FBAWMAF6BAgCEAE&url=https%3A%2F%2Fwww.themotorcyclebroker.co.uk%2Finvesting-in-a-honda-cb750-sandcast-be-aware%2F&usg=AOvVaw0uhcgsGZQtuSL0J2xwpKFa
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According to the sandcast forum the cases were painted, chain breakage was common but I dont think the scare mongering in that write up is worth listening to too much, plenty of die cast cases have had the dreaded chain damage as well, fortunately my sandcast cases are in perfect condition as well as all the original threads , but to be fair damaged cases no matter how well repaired will affect the value in some way
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This bloke increasingly irritates me. On the face of it his articles, YouTube videos and CMM pieces draw attention to the dangers of buying non 'investment grade' bikes whilst subtly promoting his own services.
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I have lost count on how many sandcast 750 engines I have built, I know it was 5 last year alone. Most have had not paint on the cases but, I have always found paint in the starter motor housing and paint under the little coloured sticker . This means that the rest of the paint has come off over the years.
The chain never came off, it was the front sprocket that was tooo small and it back lashed / whipped and damaged the case ;)
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I like how he suggests that he has special knowledge but at the same time shows that he doesn’t...for example “many of the original sand-casts had their engines replaced with die cast units under warranty” but clearly has no fucking idea how many otherwise he would tell us....... tit.
Plus he expects us to believe that Honda launched their hugely important breakthrough bike with engine castings that were porous and brittle *like an aero bar”, thus running the risk of ruining their reputation in the massively important usa and around the rest of the world..... just to beat kawasaki to a launch.
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so is he saying that casting other than die-casting is always brittle asnd full of air bubbles......
I always thought that pressure die-casting was for complex shapes where the metal would tend not to flow into all the corners under gravity alone, not to prevent air bubbles.
curious as to how well informed he is about metallurgy....as I am not buying his expertise on Hondas
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He seems to be confusing various elements each with another and then placing odd reasoning on top of crap foundations to delude himself. How could you trust him to judge (as his other writings say) to advise people on purchase of anything really. Looks wholly unreliable as a scource.
Specifically, seems to be confusing mould type with pressure or no pressure method of casting.
Speaks as if it was the first engine Honda had cast, with no experience before this :)
Crankcase "drilled" as obviously not heard of line boring ;D and understand what this entails.
Sadly lacking in very fundamental knowledge.
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AFAIK the early Sandcast engines were Sandcast because Honda had no idea whether they would sell or not and Sandcast moulds are much cheaper than tooling up a Die casting Production Line.....especially on a Prototype machine (and don't forget how revolutionary the K0 was back in 1969....or 1967/8) when Prototypes were probably first being made, where you might need to make a series of modifications following the Trials of the finished machine - AND the finished Engine Castings......when you had figured out the relevant parameters influencing machinability, tooling, access for servicing, longevity, strength, scrappage rates (of the castings) etc etc.
Die Casting was certainly a much better, cheaper - per part produced, faster and reliable (repeatable) process than Sandcasting and ensured that complex changes of cross sections and lengthy (relatively speaking) chambers needing to be properly filled with molten alloy were sound......perfect for a CB750 engine, which compared to my Triumph cases from the 60's makes them look positively agricultural !
In this article he fails to mention that if or when a Sandcast engine blew up....the only Service replacement available would have been a Die Cast engine as once the Die Casting Production line was up and running, Honda wouldn't make any more cases using the Sandcast method.
In a past life I was involved in specifying/ testing/ inspecting castings of all shapes, sizes and complexity and part of the 'Contract' with the Foundries was 'how expensive the patterns/ moulds/ dies were to produce; how long would they last (i.e. how many pieces would they make before they required reworking - or scrapping) and whether we (the Buyer) wanted to pay for them outright and own them (so we could take them to another Foundry if this one didn't perform) or whether we wanted to pay for them via an extra charge on each casting produced'.
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Didn't MV Augusta use sandcasting for all of their engines up until at least the late 1970's?
Surely, if there was a fundamental problem with this process for engine component production they would have used an alternative?
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MV probably never planned on Honda volume (or wore out their dies)
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Well here's the man himself with all of his BS.
https://www.youtube.com/watch?v=gA3FFe-lSsw
Similar video on the Z1 as Andrew said.
Much better to listen to Trigger as he has actually restored loads of those engines including fixing chain damaged casings.
Here is what steve Swan founder of Sandcastonly forum commented.
Steve Swan
9 months ago
This expert is obviously misinformed and possibly delusional. The first 7,414 1969 CB750 Honda engines were DEFINITELY produced using the Sandcast process. They were diecast beginning at CB750E-1007415. Sandcast and "gravity cast" are for all PRACTICAL definition, the same thing. Diecast or permanent mold tooling is not cheap and Honda had no idea if sales of their new bike would justify the investment in the tooling. It is quite common for manufacturers to build prototype and pilot series runs using the Sandcast process because it is much cheaper. The intro on this forum, http://www.sohc4.net/cb750-sandcast/, about the Sandcast motors is chock full of incorrect information. The writer obviously knows little about which he speaketh and writeth. Your Sandcast engine cases saw quite a bit of sand.
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The man obviously knows nothing about metal casting and the costs involved in producing a single set of dies back then. A simple pair of blow moulding dies for blowing plastic bottles can cost up to £50,000 and can be very easily ruined.
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He's a writer by trade so can tell and sell a good yarn.
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Don't forget that these things are not Sandcast like an early Meriden triumph, they are gravity die cast, a vastly different method. Or is the information freely available out there also bullshit.
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(http://cb750sandcastonly.com/coppermine/albums/userpics/10004/normal_setember_10th_till_22__2012_Alanya_holiday_photos_027.JPG)
sandcast casing
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Like an Aero bar. (https://emoji.tapatalk-cdn.com/emoji16.png) ;D
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They sealed the inside of the cases really well, and the outside was protected in silver paint
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So we're they gravity die cast or really sandcast?
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Sandcast is gravity casting, cant see why Hond would have dies made and not pressure feed them
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Where’s Richard? - given that he’s been casting stuff for longer than I’ve been on this planet?
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Sandcast is single use sand moulds made around a pattern in usually 2 or more pieces and is smashed open after use to remove the component. Gravity die cast uses permanent or semi permanent dies that have the advantage of being able to tilt to aid the metal flow. Completely different processes, with the exception that the dies can sometimes contain a sand core.
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I've always found this bloke's smug, self satisfied, self promoting magazine articles intensely annoying...... I had no idea he produced videos that are even more irritating........thanks for that >:(
Mick.