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V7 Sport Cylinder Problem.

Stephen Richardson

Tuned and Synch'ed
Joined
Oct 25, 2021
Messages
27
Location
Magnolia TX
Hi,
I'm in the process of rebuilding a 1973 V7 sport 750 engine. The cylinders are 82.5mm diameter. One of the cylinders has some of the chrome cylinder lining flaking off.
I'm looking for advise on what options I have for repair or replacement. I'm trying to avoid buying a new cylinder kit as I'd like to keep to a low budget if possible considering the bike will never be ridden much.
Are there other models that are interchangeable with my cylinder heads? Is re-chroming the barrels an option? ...who does this? ....Thanks!
 
Hi.

Unfortunately you have to either repair or replaced your jugs and pistons. There is no cheap way to do this and if you foolishly run the engine without fixing this problem first, you will destroy the crankshaft from the flaking metal.

Re replating, I’ve know people who used labarronspowersports and these are their current prices:

F00F77BB 1F5A 4E61 8E04 245AF0946A5E

However most people I know opt for new jugs and pistons from Gilardoni.

About $800 everywhere for 2 complete sets.

9CF1478F 24E1 4E94 87B2 A83083F88FD8

I bet Todd might even have them in the STORE tab.

Worth sending an email to him.

If he doesn’t, call Mark Etheridge at Moto Guzzi Classics in Signal Hill, CA. He will I guarantee. He may very well have a used set as well. He has tons of vintage stuff in his shop.

Good Luck!
 
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I honestly do not know for sure as I've never done that before. I would check with whomever you want to do the replating of the Nikasil.

Personally, given the couple hundred difference, I’ve always recommended new Gilardoni everything so I cannot give you a solid answer on replating and piston requirements.

Maybe one of the others here has more direct experience with that and will chime in here.
 
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Yes, I agree, I just got a quote to re-plate the bores for $257 per cylinder from Millennium Technologies, plus rings ect..ect
The issue I'm now having is finding a supplier for the cylinder & piston kits, nobody seems to have them in stock any more?
I have a call in to Mark Etheridge at Moto Guzzi Classics ...fingers crossed!!
 
Yes, I agree, I just got a quote to re-plate the bores for $257 per cylinder from Millennium Technologies, plus rings ect..ect
The issue I'm now having is finding a supplier for the cylinder & piston kits, nobody seems to have them in stock any more?
I have a call in to Mark Etheridge at Moto Guzzi Classics ...fingers crossed!!


Original bores were chromed, not Nikasil. Stripping the chrome and then adding Nikasil is what would have to be done. Gilardoni only does limited runs periodically. You have to catch them when they are available. This is a common occurrence. You may be able to use cylinders and pistons from other round head configurations. I'm not sure exactly which parts would be needed. Possibly pushrods and rockers if you update to a different cc configuration.

An additional option is to sleeve the cylinders you have and bore the sleeve for the pistons you have. Tricky in that a ledge has to be kept at the bottom to hold the sleeve and getting the correct piston clearance for an iron liner.
 
There you go!

I used the term Nikasil interchangeable with “chromed” as that is the BMW lingo which I was familiar with but it is technically inaccurate. Nikasil was actually a massive improvement over straight hard chrome.

I don’t think I’ve ever heard of anybody stripping the chrome and replating again with chrome again as the metal compound (Nikasil) is 10x harder and much more durable. I think US Chrome in Wisconsin is the only place I can think of that you can actually get true rechrome in the USA if desired but again not exactly sure from no firsthand knowledge.

John is far more accurate and I appreciate the correction.

I also did not know the production run methodology of Gilardoni but it makes sense and given the Covid turmoil in Italy right now, production has probably been put off, causing the nonexistent supply right now.

Gilardoni is in Mandello del Lario, by the way, just 1.5 km down the road from the factory; gilcil.it
 
The V7 Sport has a 70 mm stroke, the only other models with the same stroke are the V700 and Ambassador. Ambassador cylinders and pistons would fit, but the compression would be slightly lower and you may need to machine the pistons for intake valve clearance. Ambassador Gilardonis were briefly available a few weeks ago, but were gone in just a day. Pistons from any engine with a 78 mm stroke (Eldo, T, T3, etc.) will not work unless the cylinders are modified - the pin is 4 mm closer to the crown of the piston.

If your original pistons measure within specs. published in the original shop manual, then they can be reused, I've done this several times on customer V7 Sports. The problem will be finding rings - Deves has none last I checked, nor does any other of my usual suppliers. Edit: HMB Guzzi in Germany shows ring sets as available: hmb-guzzi.de/Piston-ring-set-825-mm-V7-Sport-750-S-750-S3

I prefer Millennium Technologies when it comes to replating. They've done nearly a dozen pair for me and the work is always perfect. If you send them the pistons and rings, they will hone to piston size and gap the rings for you.

HMB Guzzi also has an engine upgrade kit available: hmb-guzzi.de/Engine-upgrade-V7-V7-Sport-750-S-750-S3
 
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