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CB750 K5 Dilemma

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Trigger:
The bike as it is ,is not really worth much and the engine cases are scrap in my book if they have been vapour blasted  :o

Brett72:
Why do you think the cases are scrap if they have been vapour blasted?

Trigger:

--- Quote from: Brett72 on January 25, 2021, 11:09:47 AM ---Why do you think the cases are scrap if they have been vapour blasted?

--- End quote ---

Because vapour blasting takes quite a few microns off the bearing housings and mating surfaces. Had loads of engine in with problems because they have been cleaned the wrong way  ;)

SumpMagnet:
There's a couple of bikes, from the many I have owned, that I regret selling and would buy back if I could.

But...If I did ever find my old 1100 Katana, or my old Gpz1100A1 ......what would I do with them? I would have to restore them exactly as they were, so the thing was how I remembered. But, both were sold as they were big, heavy, old school dinosaurs that were too fast for their chassis and brakes, and while I did uses them everyday, I wouldn't be able to now. The KAt went because I had no garage, and had another bike to use during winter...but I had to keep it insured/taxed etc. for fear of theft....and I just couldn;t afford it. I sold the Gpz when I ended up going into central London every day and the running costs were crippling me. If I could have stored them....well...different story. But no garage

They also, I suspect, would not feel the same now. Perhaps the memories are better than the metal would be?

Now I have a new project that I can take in whatever direction I fancy, it's not trying to recreate what I had before, and can be whatever I want. Not...it was that colour, with that exhaust and those bars....oh and I fitted that seat.....

Laverda Dave:
Who did your vapour blasting and did they vapour blast the insides of the castings as well as the outside? As Trigger implies, blasing the insides is a big no, no. The insides of engine cases shouldn't need blasting anyway as they are not subjected to road salt etc.

When I take my cases for vapour blasting I give them strict instructions NEVER to blast the insides or around any bearing housing be it shell, ball or roller. The company I use is called I Cleenz Machinez based in Penge S.E. London. They are used to doing this type of work on alloy engine castings and are really very fussy. I have never had any problems with their work and I dont know anyone who has. They use old 'blunted' vapour blasting media, new media has sharp edges to clean away scale and corrossion quickly but this can embed itself into the soft alloy of engine castings and especially around bearing surfaces. You might think it's all been cleaned out but when the engine gets warm and media that has embeded itself into the internal walls of the castings can fall out, mix with the oil and then....disaster! There is less chance of this happening if the old media had been used a few times and has lost its sharpness but it takes longer to clean the part. I always clean the castings when I get them back at least three times with jets of soapy water, bottle brushes down the oil gallery, compressed air etc just to make sure any stray media is out. Blind oil galleries is a potential area where media collects and is very difficult to remove as it will be held there by old oil. Blind oil holes should be sealed before blasting. I don't use my parts washer to clean the parts either just in case I do introduce any blasting media to the engine cleaning fluid and contaminate it.

I've always been lucky if that's the word, and never had any problems but there are plenty of people who have suffered with wrecked engines following vapour blasting. There is a well known story from a good few years ago when someone had a CBX engine rebuilt only for it to become toast within a few miles due to blasting media finding its way into the oil after a few miles.

As long as you know who has done the work, their methods AND you clean it up afterwards you should be OK but vapour blasting can be very risky.

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