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1971 CB500K0 Resto 3/71 VIN 1000896

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AshimotoK0:
I deliberated over how to remove the yellowy brown film on the inside of the crankcases. Neither my ultrasonic cleaner on maximum sonics and full heating  would touch it. I was reluctant to dig out my 4l  tub of Hydroflouric acid, as this stuff is off the scale in terms of nastiness but a known cleaner used on aluminium (it used to be widely used by car aluminium wheel valeters until they saw sense). However, I found a bottle of weak sulphuric/ Nitric acid mix that a mate mixed me up ages ago, intended for 'desmutting' aluminium prior to anodizing so I decided to try that. Again, pretty nasty stuff but deffo lower league than hydroflouric acid in terms of nastiness.   I tried brushing that on the inside of the cases (obviously keeping it off any bearing surfaces etc.) and that semed to work fairly well. I then pressure washed it off with water and then hot tanked it in my US cleaner bath to removed all traces of the acid.

AshimotoK0:
Just appreciating what a lovely engine the CB500 is to work on, particularly compared with the CB750.

Still cleaning up the crankcases ready for paint... bit of a tedious task, so doing half an hour here and there until they are prepared enough. I still need to improvise a curing oven for the paint. I kept our old kitchen oven that would have been perfect but that's at work and I am not allowed access to work, so going to try to impovise an oven at home. Using our kitchen oven is a big no-no, as my wife Cathy suffers from quite bad asthma.

Ultrasonically cleaned the cylinder head but still need to clean out the ports as the U/S cleaner softened the carbon  deposits but it's going to need my Dremel and little brushes to clean out properly.  Valves are looking fine after a clean and grinding in, with just under 1mm seat width still, plus valve stem/guide clearance is OK and valve springs well within limits .. a bit of a relief as I was thinking I might have had to send the head to Trigger & Julie for seat recutting etc.

Managed to find a decent counter shaft among my spares....Bryan ... I used one I got for £1 from Newark autojumble, so I can let you have the one back you kindly donated to me when I came down to see you. I fitted all NOS needle roller bearings including the one in the starter ring plus new bearing to the primary shaft (plus I have the other  6205 bearing (new) to fit in the cases). I bought a rare NOS gearbox output bearing (283 part) as a panic, mega money buy, when I first got the bike but the one already fitted to the gearbox shaft was absolutely fine so I didn't fit the NOS one  (may need it for my Bomber engine possibly). All of the gears look fine with no chipping or drive dog wear. Fitted the 8 new primary drive rubbers. So the gearbox is all good to go back now.

Received the 'oil guide B' in the post from Julie ... massive thanks for that.

Bryanj:
Centre selector in good order mate? And are you fitting the later selector /clutch parts? If so dont polish the original clutch case the required one with mods is slightly different and  that plate you wanted is part of the mod kit.

AshimotoK0:

--- Quote from: Bryanj on April 02, 2020, 07:24:44 PM ---Centre selector in good order mate? And are you fitting the later selector /clutch parts? If so dont polish the original clutch case the required one with mods is slightly different and  that plate you wanted is part of the mod kit.

--- End quote ---

Thanks Bryan .. I think I may just add the mod plate to better lubricate the bearing and stick with the original cover etc as the bike won't be doing many miles and I guess the ones James owns and SteveD's will have the original shift mechanism. Or is that a big no.no?

The centre selecter measured fine and no signs of discolouring ... is there anything else I should be looking for? I do have spares as it's a CB350/250K part but it looked OK to me.

Bryanj:
It might be that plate that makes it need a different cover, not  sure. The mod was for better gear detent and to locate selector drum better plus better clutch operation so up to you

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