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Neils 1978 CB550 F2 Project - Newbie Let Loose
Oddjob:
I can find 2 sets of 0.5 oversize rings and 2 genuine 0.5 oversize pistons. However Cruzinimage will be much cheaper, I'm personally not a fan of Cruzinimage as I hear bad things being said of them on the USA site amongst others, especially on ring quality.
Oddly I'm going through the same as you. I have a 500 engine which I'm converting to a 550 set of barrels, I had one set of barrels ceramic coated and then found a mark on the bores that meant I had to consider a rebore. I decided to go 0.5, got new rings and for some reason I ended up with more 0.5 pistons than I needed. Hence the extras I mentioned before. Then I found a set of NOS 550 barrels going cheap, so I bought them and had to then source a set of genuine standard pistons and rings, which I did. I now have to decide which set I'll fit, the ceramic coated set need a bore but I can't work on the bike just yet due to health problems so no rush. I may keep the NOS barrels for spares, they'll only go up in value.
Neilw:
--- Quote from: Oddjob on February 11, 2026, 10:24:24 PM ---I can find 2 sets of 0.5 oversize rings and 2 genuine 0.5 oversize pistons. However Cruzinimage will be much cheaper, I'm personally not a fan of Cruzinimage as I hear bad things being said of them on the USA site amongst others, especially on ring quality.
Oddly I'm going through the same as you. I have a 500 engine which I'm converting to a 550 set of barrels, I had one set of barrels ceramic coated and then found a mark on the bores that meant I had to consider a rebore. I decided to go 0.5, got new rings and for some reason I ended up with more 0.5 pistons than I needed. Hence the extras I mentioned before. Then I found a set of NOS 550 barrels going cheap, so I bought them and had to then source a set of genuine standard pistons and rings, which I did. I now have to decide which set I'll fit, the ceramic coated set need a bore but I can't work on the bike just yet due to health problems so no rush. I may keep the NOS barrels for spares, they'll only go up in value.
--- End quote ---
I guess I need some more information. I'll put an existing ring in each bore and measure the gap. I assume that if they are within tolerance, then replacing the pitted piston and the chipped pistons with std pistons and rings is an option? i feel out of my depth here :-)
Oddjob:
If you use a used ring and it's within spec then yes stay standard. Change the pistons though. However you'll normally find it will be out of spec, then you're left with wondering if it's the rings which are worn or the bores or both. Only with a set of new rings can you be certain. I did this test on my NOS barrels and you'd expect them to all be at the bottom of the spec range but in fact they were around the middle. Wasn't best pleased by that but what can you do. If you were local I'd pop round with a NOS set of standard rings and we could see what they measure up at. However check the bores first, with that amount of damage on the pistons I'd expect some on the bores as well. Maybe post some pics of the bores.
Bryanj:
There are several firms selling piston kits, Dave Silvers has 0.25 os kits BUT nearly all the 500 bolcks i have bored did not clean at o.25 and had to go0.5 due to "barreling"
Cruzin only sell 0.5 and 1.0 as does an English firm i have bought from.
I know Trigger used Cruzin and i have done a few 400 recently using their kits, the us problems i have read about all seem to be 350 four and they are VERY critical on bore to piston clearance.
Cruzin piston kits usually arrive within 8 days and i have had uk parcels take longer
Murf:
When I opened up my 550 engine I found the piston tops had score marks that look like they have come from a belt sander with 60 grit abrasive. I have to assume that is exactly what it is and that some tosser ‘cleaned’ the pistons on a belt sander!!!??.
Anyway I decided to replace the pistons and after looking around I got these IMD ones which look OK, the company is in the U.K. www.imdpistons.com and were very helpful on the phone, the pistons are made in Taiwan and look good. A lot of pistons are made in Taiwan. The pistons come complete with rings, gudgeon pin and circlips.
I have got standard size as my bores seem ok.
If you do change your pistons, and I would, then you need a full set. If you stick with what you have and just change the damaged pistons then you will need genuine Honda pistons so that the weights match.
You say you are a bit overwhelmed with it at the moment, don’t worry this will just become normal life after about a month🙄
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