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Neils 1978 CB550 F2 Project - Newbie Let Loose
Bryanj:
Yes to both as when you remove the head it disturbs the base and if you dont replace gasket and O rings it may well leak later
Neilw:
--- Quote from: Bryanj on February 02, 2026, 03:39:21 PM ---Valves and seats first then pistons/bores
--- End quote ---
Update 5th Feb 2026
I've stripped the top end down and it doesn't really look too bad. I'll post some pics later today.
I have a question about the Piston rings. I've managed to break the top one on 3 of the pistons while removing them from the bike. I always planned to replace the rings, but - how do i know what size are in there and what size to get? I have some feeler gauges, but I don't have a micrometre to measure the bore. Is there a straightfoward way to determine what you have and what to get?
Bryanj:
Normaly it will have the size near the end of thecring, if nothing suspect standard.
In all honesty you should be able to measure sizewith a steel rule down to 1/4 of a mm which is the step sizes for rebore, or buy a pair of cheap vernier calipers of ebay.
You cant buy individual rings they come in sets for a piston
Murf:
The switch has had 50 years of use and abuse ☹️ and although it is nice to repair things and keep them going I have replaced mine with after market ones from David silver. It’s not the cheapest option but will help give you the best chance of reliability.
I would also order a new fuse box while you are at it, the one you have has already had a bypass so is probably knackered, as they tend to be.
Also give the harness a clean, pull the connectors apart to make sure they are clean, check and clean all the earth connections. Then sort of take it from there, checking, cleaning and redoing parts of the electrical system as needed.
The electrical system is the part of the bike that has the greatest ability to leave you sat at the side of the road waiting for the AA. it’s worth spending some time and money on if you are going to use the bike.
Good luck with the project, they are nice bikes to work on.
Neilw:
--- Quote from: Murf on February 05, 2026, 11:08:41 AM ---The switch has had 50 years of use and abuse ☹️ and although it is nice to repair things and keep them going I have replaced mine with after market ones from David silver. It’s not the cheapest option but will help give you the best chance of reliability.
I would also order a new fuse box while you are at it, the one you have has already had a bypass so is probably knackered, as they tend to be.
Also give the harness a clean, pull the connectors apart to make sure they are clean, check and clean all the earth connections. Then sort of take it from there, checking, cleaning and redoing parts of the electrical system as needed.
The electrical system is the part of the bike that has the greatest ability to leave you sat at the side of the road waiting for the AA. it’s worth spending some time and money on if you are going to use the bike.
Good luck with the project, they are nice bikes to work on.
--- End quote ---
I've ordered a replacement switch unit, figured it would be the cheaper option, and if I can repair the original when I'm finished, I'll do that and sell it on (I love the patenia on it!).
Regarding the electrics - I plan to upgrade the fuse box and maybe at the end put electronic ignition in, but that's a long way off.
The wiring and connectors, especially under the left cover, are dusty with 50 years of accumulated grime. How do i go about cleaning the mess. Do i spray it with something?
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