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V7 Sport piston/cyl size "CC"?

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Missionguzzi:
Continuing the teardown and cleaning of 1972 V7 Sport.  Aside from the Woodruff key issue, posted previously, I found another puzzle.  The piston and cylinder sizes are both marked "CC" (see pictures).  The manual lists sizes A, B and C, but not "CC".  Has anyone heard of "CC" and know what it represents?  Is it possibly unique to only the V7 Sport?  I'm ordering standard sized rings, and I assume they'll fit, but maybe this is an odd duck (or goose....).  Otherwise, pistons are shaped as they should be.  My digital vernier isn't calibrated and isn't accurate enough to get a good reading at these increments.  Thanks for your input.

guzzisteve:
Seen a lot of Guzzi pistons but never CC, I would mic it for sure & the cyl.

I will bet Joe W knows, he's seen more Sports than anyone I know. GuzziDoctor.com or similar.

Antietam Classic Cycle:
Are you having the cylinders replated? Even if the chrome looks good, I would recommend you do so.

cliffrod:

--- Quote from: Antietam Classic Cycle on July 14, 2024, 04:52:24 PM ---Are you having the cylinders replated? Even if the chrome looks good, I would recommend you do so.

--- End quote ---

Agreed.  If you’re using someone like Millennium https://millennium-technologies.com/ to replate your cylinders instead of purchasing replacement nikasul-plated cylinders, I would recommend calling them first & before you spend any money. 

If your cylinders have not already been replaced or replated, one or the other needs to be done.  It is not an option.  Cleaning the sludge trap on crankshaft during such a rebuild is also not an option imho.    Ask me how I know…

2nd edit- that “notch” or relief on the piston is not present on 73 V7 Sport pistons.  I can’t claim to be an expert & to have seen many different v7 sport pistons, but all the ones I’ve seen were like mine- round dome with concentric flat top around it.  My opinion- that CC may denote the cut-out version piston, which would lower compression versus the more typical complete round dome and flat concentric top.

Missionguzzi:
The piston with the cut-away for the intake valve is a stock piston, and it shows on the parts diagram and workshop manual.  There could have been other variations, but this is definitely a standard item.  The later Tontis had a flat piston dome with smaller intake cut-away.
Sludge trap was cleaned and had the usual "crescent moon" of sludge against the outer wall, otherwise the crankshaft is perfect.
Chrome bores have been beat to death.  I've rebuilt a couple dozen Guzzis, at least, over the past few decades.  Some have terrible chrome, some have perfect chrome.  As a retired manufacturing engineer (with plating experience), I suspect the Guzzi factory in the early 70s didn't have good process control or quality control, thus had very inconsistent plating.  Chrome bores were used as standard for decades on Lycoming, Continental and Mooney aircraft engines, and ran between rebuilds for something like 12-15,000 hours (equivalent to over 100K miles), with rare failures due to bad chrome.  I've used good chrome cylinders with no problems, and inspected after tens of thousands of miles with no deterioration (such as an Eldorado with over 70K miles and perfect chrome).  I've also had low-mileage chrome cylinders that were almost completely devoid of chrome.  And I've used many Gilardoni Nigusil kits on the bikes that needed it. 
The "CC" could indicate a special piston for V7 Sport only, but the parts book only calls out A, B and C sizes.   My old digital vernier isn't calibrated and is inconsistent, so I can't get a reliable measure.  Maybe time to get a new one....
Thanks for all the responses.

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