V7 Sport catastrophic failure

[Missionguzzi]

A friend brought me his 1972 V7 Sport after it stopped running during an easy Sunday-morning ride. I checked first for spark - got none on either side. Removed the valve covers and noticed that the valves on neither side were opening or closing. Engine was able to turn over freely, but camshaft wasn't moving at all. Removed both jugs and the timing cover and found the cam gear broken into 2 big parts and a couple of small pieces. See pictures.  Wondering about potential causes other than metal fatigue.  Camshaft seems OK, but could have undetectable defects, cam journal appears unscathed.  Also needing a compatible camshaft (850-T, T-3?) and all 3 timing gears to replace the broken or compromised parts.  All input welcome.  Thanks.








the western wind poem

[Antietam Classic Cycle]

That happens on Ambassadors and early Eldos sometimes and is chalked up to a casting flaw. The "small hole" gears usually don't fracture, just the roughly cast "large hole" ones.

Doubt there's anything wrong with the cam. It wasn't used on any other model sold in the US - the grind is unique. A T and T3 cam would work. 

Check with Mark Etheridge at Moto Guzzi Classics (562-986-0070) and Paul Szostak (his contact info. is here: Michigan Rep. - South https://www.mgnoc.com/staff_and_reps.html) for the gears, Paul might even have a cam. Joe Walano "The Guzzi Doctor" might also have what you need. https://theguzzidoctor.com/

[Don G]

Wonder if any valves met a piston?

[Huzo]

Wonder if any valves met a piston?

First thing I thought.
The valves themselves will not have collided with each other because the camshaft is keeping them in time relative to each other, but your fear of piston collision is well founded

[faffi]

I would remove carbs and exhaust for a visual inspection of the valves, then do a compression test after reassembly if there were no visual clues of any bent valves. A bore scope can also be telling. As I type, I came to think that a leak-down test as it sits can tell you everything you need to know about the condition inside each cylinder.

[Dukedesmo]

Yikes, catastrophic indeed.


I'd be amazed if there wasn't some piston to valve interface on at least one cylinder. My LM2 had a piston to exhaust valve interface for no obvious reason (timing and clearances were good and nothing broke), possibly sticking valves or over rev? I'll never know.


But the engine didn't stop, rather it just lost power and got me home for me to find 'mildly' bent (both) exhaust valves and ultra-low compression.


Similarly, my Son's car had the cambelt 'stop', didn't actually break, rather the teeth around the crank pulley sheared off so it just stopped turning but, all the exhaust valves were bent.


Whatever damage it did, hope it's not too serious/expensive to fix, good luck.

[Huzo]

Are they original gears or retro fits ?

[Missionguzzi]

Thanks for all of your responses.  I believe the timing gears were original, but who knows what might have happened in the past 53 years?  Yes, indeed, the right side exhaust valve was slightly, visibly bent, and the intake may have "kissed" the top of the piston.  Left side looks OK, but I plan to disassemble to check and lap the valves anyway.  With luck, the camshaft is still good.  I know it's unique and more aggressive than the T/T-3 cam, so would be nice to retain it.  I'll have to count the gear teeth on all 3 gears to try to find a matching set.  I don't really know if the other gear teeth configurations would work, as long as they're part of a matched set.  I don't know why not, but it could make valve timing more difficult.  I sure wish I could retrofit a timing chain to this crankcase, but the oil pump won't allow that.
Thanks again for sharing your thoughts.  Hope I can get this back together correctly and help this old Sport get back on the road.

[JoeW]

As far as I know, the cam gears are the same in the Sport as the Eldo and Ambo. The crank gear is different. I know that the gears are listed as sets in all the parts books but, they are not coded as "matched" sets. I have mix gears with no issues, especially when I see a large hole cam gear.

[Missionguzzi]

Joe W, I found a complete set of gears identical to the broken ones.  I believe the cam gear is the "small hole" type, based on pictures I could compare. And the gear that broke is also the small hole type.  I guess they weren't immune to defects.
If possible, could you elaborate on what's different about the crank gear?  It seems like that would have to be a fixed shape, considering the slot for the woodruff key.  If it's different, what should I look for?  Thanks again for all the help.

[Antietam Classic Cycle]

Joe W, I found a complete set of gears identical to the broken ones.  I believe the cam gear is the "small hole" type, based on pictures I could compare. And the gear that broke is also the small hole type.  I guess they weren't immune to defects.
If possible, could you elaborate on what's different about the crank gear?  It seems like that would have to be a fixed shape, considering the slot for the woodruff key.  If it's different, what should I look for?  Thanks again for all the help.

The V7 Sport crank gear is different than the Ambo/Eldo one. On the Ambo/Eldo it has a "snout" that protrudes through the timing cover, the seal runs on the "snout" and the gear is secured by a large hex nut on the end of the crank. On the V7 Sport, none of it protrudes through the timing cover, the seal runs on the alternator rotor, and the gear is secured by a ring nut and lock washer.

[Missionguzzi]

Charlie M., thanks for clarifying that detail.  Sure as hell, the set I ordered has the snout on it.  I'll have to determine whether I can re-use the old crankshaft gear (I know that's not recommended) or find a good machine shop which could mill off the snout to the correct dimension.  When I was still working, I had a good machine shop in my manufacturing plant.  Unfortunately, I've moved and no longer have that capability.  The V7 Sport was a fine motorcycle, but an odd duck in the goose family.  Too many unique parts and features to deal with a half-century later.