Painting Crankcases

[Mr_Sheene]

This may not work! I have been on this site for two years and have not even managed to successfully send an e-mail to another member yet, so please bare with me. A couple of years ago, in a fit of madness, I broke my own rule and bought a 1970 CB750 on e-bay. I think that the vendor was well meaning but not talented. As a result, I have not been able to ride a bike I only bought for that purpose, so I have decided to strip the engine and with the help of a talented friend, re-build it. The cases appear to have been painted with a rattle can and need to be professionally cleaned and painted in the correct colour of engine paint. I live in Essex and am prepared to travel 150 miles or so if necessary.  I have been told that 'Ice Blasting' is the best way to have them cleaned and then I need a company that can provide a good quality finish in the correct standard and quality of paint. Does anyone know of companies that provide these services and is there any advice on the subject that may prove useful?

[RGP750]

Hi Mr Sheene.
Welcome to the forum, (albeit from lurking in the shadows )
If you put crank case painting in the top search bar you will fin hours of reading and
pick what suits you .
ask again when you have digested as much as you can take .
Good luck
Rich

[Mr_Sheene]

I don't know why that didn't work before but it did this time, thanks. I have many hours of happy reading ahead of me. If you think that I'm not very good at this, you'd be correct but I can only get better. On the other hand, I may forget what I did and have to go back to lurking. Can I have my status changed to incompetent? 

[Nurse Julie]

Welcome to the forum Mr Sheene. You will find all the answers you need on the forum somewhere. What is wrong with the engine / bike that has made it unusable?.

[BigAl (Alan)]

Viewed a CB750 at the Stafford Show, Oct 2017 (as small image) with a very good engine finish.  If he or she contributes on here, then definitely the person to ask.

[MarkCR750]

I don't know why that didn't work before but it did this time, thanks. I have many hours of happy reading ahead of me. If you think that I'm not very good at this, you'd be correct but I can only get better. On the other hand, I may forget what I did and have to go back to lurking. Can I have my status changed to incompetent?

Hey, hey, hey!, if anyone is getting their status changed to incompetent that’ll be me thank you very much!
Welcome Mr Sheene 👍

[Mr_Sheene]

Sorry about the delay, I went for coffee. There is a picture of the bike in 'Gallery'. I put it there the other day when I was trying to learn how to use the site. Without boring you, I bought the bike to cheer myself up. I went with a couple of friends to Swansea to collect it and it came down like stair-rods all day. As  a result, I didn't test ride it. Mistake? The vendor appeared to be a nice bloke and gave the offer of leaving it, if I wasn't happy but I think he was more optimistic than talented. He started the bike easily and it sounded okay, so I took it home. A few days later, I put fresh fuel in it and went for a ride. It was difficult to start and sounded like a bag of nails but I thought that I would take it easy until it warmed up. I have only ever ridden one other bike that explained the term 'wooden brakes' and that was a Harley. After 500 yards I decided that this was the second, so I took it home. I have a friend who is an experienced motorcycle mechanic and we went over the bike together. He was happier than me. When I looked at the carbs, one of them had a cracked housing where the main jet had been cross threaded. The repair was a jubilee clip to close the crack. I couldn't understand why the clips holding the upper of the fork bellows was not sitting correctly, until I realised that the bellows were on upside down. When I tried the kick-start, it wouldn't return without help. Do you get the picture? I can fix the bellows and strip the brakes in my sleep but I have never stripped an engine more complicated than a 'British Twin'. Bill will help me. The vendor gave me a list of parts that he had used to build the engine and there doesn't appear to be much that may need replacing. As I want to keep the original engine/frame combination, I decided that it would be best to re-build the engine. I have just read an account by Trigger on cleaning the cases and may become a lurker again!

[mike the bike]

Never heard of ice blasting, I've just googled it.   Most intriguing I must say.

[royhall]

I think these Honda's are easier to build than a British twin. I'm doing a Triumph twin right now and they are fit where it touches quality. Honda's are so well made they almost put themselves together. With a bit of help on here you will manage just fine.

[RGP750]

Yes Roy i agree, Easier than a British bike to rebuild.
Just do it bit by bit.

[Trigger]

Welcome to the mad world of the SOHC, did see your 750 in the gallery, has a few wrong parts, should of asked on here before you took the plunge. The advise is free 

[Mr_Sheene]

Hello Trigger, I would have asked, if I had known the site existed at the time I was bidding. I'm from an earlier age. For example, my mobile is a phone! Also, as I said, it was a mistake to buy on e-bay, as there is a certain pressure not to lose the item. I believe that it's called 'auction fever' and I seem to have caught it on this occasion. I paid £5k for it and would have been happy if I could have simply ridden it. I am not looking for a concours winner or an auction champion, I just wanted a Sunday morning ride. If I can get the engine sorted, the rest of it is workable, although I will change the colour to the candy red alternative. I can't get original carbs as they appear to be unobtanium but I have got a decent set from a K1 to replace the set that are on it. All advice and observations are welcome. I'm too old to be 'proud'. The cylinder head seems to have a 'sand cast' finish. I don't have delusions of grandeur and know that this head was common but was it common to all CB750's.  Some clot in the past has obviously tried to lever of the head and damaged a couple of fins but I put that down to patina as I don't have the missing bits to get it fixed. What is your opinion of 'ice blasting'?

[Sgt.Pinback]

Never heard of ice blasting, I've just googled it.   Most intriguing I must say.

You call it vapour blasting.

Works great.

[Mr_Sheene]

I know marginally less than the square root of nothing about engineering but I love the internet. Vapour blasting, also known as wet blasting or liquid honing uses water and an abrasive medium blasted at the component. I think that these are very small glass or plastic beads. The water buffers and lubricates the particles on impact allowing fine finishes to be produced without damaging the component. I was going to use that until I was directed towards ‘Ice Blasting’, which uses dry ice that evaporates on contact taking the muck with it (it says in the blurb) and leaves no residue to block oil-ways etc. I was happy with that until I read Triggers entry about acid baths and ovens to get oil out of metal, so now I am doing more research. Thanks for the input though as it is the only way that the job will get done. My first entry asked if anyone knew of companies for cleaning and painting that can be recommended in south-east England. The request still stands, although if they are that rare I will consider going further afield.

[Trigger]

Never heard of ice blasting, I've just googled it.   Most intriguing I must say.

You call it vapour blasting.

Works great.

Vapour blasting is glass bead and water  ice blasting is dried ice