V7 Sport piston/cyl size "CC"?

[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]

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

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.

[Antietam Classic Cycle]

I've rebuilt six V7 Sport engines, years '72, '73 and '74, and every one has had pistons that look like those in the original post. The relief is for clearance with the intake valve. Ambassador pistons are shaped the same, but with no relief, and are .5 mm larger diameter.

Unless something has changed recently, there are no new V7 Sport cylinder kits available - not from Gilardoni or anyone else.

[John A]

Chrome plating on iron cylinders is what aviation cylinders are. The trouble comes from chrome plating on aluminum cylinders because the expansion rates between chrome and aluminum are too different .There were other manufacturers that have tried it and none have been successful for longevity.

[Antietam Classic Cycle]

Chrome plating on iron cylinders is what aviation cylinders are. The trouble comes from chrome plating on aluminum cylinders because the expansion rates between chrome and aluminum are too different .There were other manufacturers that have tried it and none have been successful for longevity.

My old ('50s and '60s) Lawn-Boys have chrome-plated bores in alloy castings. The difference is that they're pre-mix 2-strokes, so lots of oil in/on the bores.

[John A]

My old ('50s and '60s) Lawn-Boys have chrome-plated bores in alloy castings. The difference is that they're pre-mix 2-strokes, so lots of oil in/on the bores.

Those were great mowers alright, I didn’t know they had chrome on aluminum bores. It worked there!

[testa_di_formaggio]

Sorry for off OT comment. (Not really). I went to the WSB races at Brainerd MN, think it was '91 or '92. Some locals said "make sure to camp down in Turn 3 and 4". OK. Saturday night, huge party ensues. OK. BIG bonfire. At the base of which, was a Honda 350, that's yet another story. Later in the festivities, some guy backs up to the fire, and throws a dozen or so LawnBoy mower decks on it. WOW !!! Never saw magnesium burn before !!! And didn't look at it long..... I must admit that I considered putting on such a show at subsequent Guzzi rallies I attended, but was talked out of it. We were already having enough fun throwing tomahawks....

TdF

[cliffrod]

I was mistaken- just checked my original pistons (marked C) and they do have the relief.  Must have been thinking of the V700 pistons of current projects.  I replaced my original V7 sport parts with upgrade nikasil cylinder kits from Moto Guzzi, long since obsolete.  Part number is on the old box, just in case it helps someone-





What the CC means-?  It may be special or a simple mistake resulting in a double stamp.

As far as chrome bores.  your bike, your rules.

[Canuck750]

I found a picture I took years ago of a 73 V7 Sport engine I was tearing down. I would bet the double C stamp was just a manufacturer miss stamp.



I was able to purchase new Giladorni kits. On others I sent the original pistons with new rings and the old cylinders to Millenium in Canada

I would pull the crank and rod big end shells, along with the crank bearings and inspect / measure for wear and chrome flakes.  6 out of 7 of these old pre oil filter Guzzis I rebuilt needed a crank grind, oversized mains and shells and the oil pumps needed replacement.

[Missionguzzi]

The "CC" could be a double stamp, but maybe "intentional".  It's on both pistons and both jugs.  Don't think that would be just a random error.
As mentioned, I've rebuilt perhaps 25 or so old (pre-Nigusil) Guzzi engines in the past few decades, just as a hobby.  I know some pros out there have done many more.  In all those, maybe 1/3 had perfect chrome, 1/4 had really stripped out chrome, and the remainder had minor flaking at the top of the bore, mostly in the squish zone of the combustion chamber.  I changed any that were damaged with Nigusil kits or had them plated elsewhere.  Those with good chrome, usually mid- to high-mileage, I figure were made on "good days", when the plating process was all in spec (temperatures, solution, duration, cleanliness, etc).  If any of those parameters go out of spec, it will affect the plating quality, even if it "looks" fine.
I never had to turn a crank for excessive wear or galling.  All have been standard and in good shape.  Maybe just lucky?  I tend to think these were generally pretty good components, as people rode older Guzzis MANY miles before needing rebuilds, even the old, pre-filter models.  I believe proper care (oil changes) and climate make a difference.  Bikes I've gotten in the dry southwest seem to be in better shape than those which come from humid places, particularly the Gulf coast, with warm, humid and salty air.
Millenium charges about $650 to plate two cylinders, and roughly the same to plate the pistons.  They like to do these together in order to size them correctly.  That's more than I want to spend, and I don't believe it's necessary with the good chrome on this 23K mileage bike.

[cliffrod]

Millenium charges about $650 to plate two cylinders, and roughly the same to plate the pistons.

??  Please explain.^^^.  I’m unfamiliar with pistons being plated.  They didn’t mention that when I’ve spoken with them.

[Moparnut72]

That is interesting. When I worked in the aircraft shop overhauling radials we had a similar situation. We would have to replace cylinders all the time. Mainly to get rid of taper or uneven wear. Since pistons were no longer available the boss would clean them up, re-machining ring lands etc. Then we would have the cylinders plated and ground to fit the pistons. I had never heard of pistons being plated. I doubt that would be a viable option but I have been wrong before, often. 
kk

[Missionguzzi]

I was surprised as well when I spoke to Millenium's technical rep.  I was only inquiring about plating the cylinders, but that I had older pistons and couldn't find new.  He said that they could plate the pistons also, and correctly size them to fit the plated cylinders.  I don't know what issues that would create, if any, as both surfaces would be slick and hard, and friction and heat dissipation would be better than stock (I suppose).  Frankly, if I had the bucks, I'd give it a try.  It remains an academic point for now.