Vincatii

Chris Launders

Well Known and Active Forum User
VOC Member
The problem explained to me by Steve Wynne well known Ducati specialist (he built the ones Mike Hailwood rode in his comeback) was the oil recommended by Ducati, which was if I remember Duckham's 20w/50w which was (then) a modern oil for watercooled plain bearing engines and contained "long chain polymers" which wrapped around bearing surfaces, the Ducati being full of roller bearings and especially the helical cut bevels just cut these to nothing, resulting in stuff like water in a very short time and you would be lucky to get 15,000 miles out of a big end, whereas a monograde oil was more suitable and Castrol R about as good as you could get. I can't remember what mileage was on mine when I got it (1991) but it was stripped and changed to R40 as soon as I got it and I think now has around 50,000 miles on it
 
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Chrish

Well Known and Active Forum User
Non-VOC Member
The problem explained to me by Steve Wynne well known Ducati specialist (he built the ones Mike Hailwood rode in his comeback) was the oil recommended by Ducati, which was if I remember was Duckham's 20w/50w which was (then) a modern oil for watercooled plain bearing engines and contained "long chain polymers" which wrapped around bearing surfaces, the Ducati being full of roller bearings and especially the helical cut bevels just cut these to nothing, resulting in stuff like water in a very short time and you would be lucky to get 15,000 miles out of a big end, whereas a monograde oil was more suitable and Castrol R about as good as you could get. I can't remember what mileage was on mine when I got it (1991) but it was stripped and changed to R40 as soon as I got it and I think now has around 50,000 miles on it


If you are really interested i have a Vincati for sale in touring trim, and the way our Aussie Peso is going it could be cheap. PM me if interested.
 

Pushrod Twin

Well Known and Active Forum User
VOC Member
Are you suggesting that I am not of sound mind?
The Honda donor frame was shaft drive. Thankfully it never crossed my mind to stuff the Comet motor in there sideways. That might have resulted in a VOC fatwa.
Yea, that's up there with me suggesting I fix my spare Auto Guzzi converter & 2 speed trans to the back of my other chopped Vincent motor, it did raise a comment or two.:D
 

Pushrod Twin

Well Known and Active Forum User
VOC Member
Sadly, the horror stories above vindicate my thoughts regarding these bikes. While several of you have enjoyed riding them, the overriding message is still that they are unreliable. I expected by now to have a staunch supporter telling us how many they knew of that had 100 million miles, but no. I have been told by several owners that theirs had done an honest 100,000Km, or in one case miles, but there is only one 750 GT to which I give any credence to. That was a member of our VOCNZ section, recently passed away, but when I first got to know him in the Italian Motorcycle Owners Club in the '70s he rode his GT two up a lot, clocking up the the 100k until a Vauxhall Viva U turned in front of him & the Ducati tipped the Viva over. At that point John stripped the engine, and broke the lead seal on the crank case, while straightening the front end. He had run it on Shell high detergent multigrade diesel engine oil which debunks the international myth started by Steve Wynne about the absolute necessity for straight grade 50 weight.
The real problem with the cranks was pointed out to me by someone with a knowledge of metallurgy & is well demonstrated by Oexing's pic of the rod. In case you hadnt noticed, there is no sleeve inside the rod eye, the rod is hardened & ground like a two stroke rod. At the confluence of the shank & the eye is the largest mass of material. When that is quenched from red hot it is the area slowest to cool, hence slowest to harden. The hardening is likely to be be both softer & thinner. It is also the area of greatest load. It all goes down hill from there.
I have also been shown several of these power plants with failed gear shaft bearing areas. They run crowded rollers straight on the shafts, the rollers pick up the shaft hardening, simply overloaded bearing area. I have also experienced two with failed gearbox main shafts. One was brought to me for opinion prior to purchase. I only rode it long enough to drop it into top gear, at which point the concrete mixer noises started, I handed it back quickly & recommended a trailer! We had another do the same thing a couple of years ago at a National VOC Rally in Central Otago.
So that is enough of the bad news stories, the solution to getting these nice handling bikes back on the road is to track them down & fit Vincent motors. :D
 

Vincent Brake

Well Known and Active Forum User
VOC Member
Are you suggesting that I am not of sound mind?
The Honda donor frame was shaft drive. Thankfully it never crossed my mind to stuff the Comet motor in there sideways. That might have resulted in a VOC fatwa.
And all you motorcycles obligatory end up in a raffle
 

Albervin

Well Known and Active Forum User
VOC Member
Chris,
Well, there's an opportunity for you - probably the first person to be in a position to build a Ducvin or Ducent!
Simply(!) put the 860 Duke engine in a Vincent rolling chassis; probably paint the engine gloss-black first for even greater appeal. :cool:
Peter B
I have seen that done and it was not pretty.
 

Cyborg

Well Known and Active Forum User
VOC Member
Yea, that's up there with me suggesting I fix my spare Auto Guzzi converter & 2 speed trans to the back of my other chopped Vincent motor, it did raise a comment or two.:D

Couldn’t think of a better way to neuter a Vincent twin. You should just do a mock-up and take a few photos. It would surely cause the rivet counters to foam at the mouth.
Probably said this before somewhere...I had both 750 GT and 750 S (round cases). Both very low k and only glitch was the S flung half of the tail light assembly into the ditch. I managed to part company with them both before any of the horrors manifested themselves. I worked at a Ducati dealership until I finally came to my senses. Some of the images are still burned into my memory banks. Have to say I did love how those bikes handled which seems weird to me now. Maybe it was just relative to other bikes of the day. They had a long wheelbase by today’s sport bike standards. Gives me hope for the Comet as it ended up longer than planned.
 

oexing

Well Known and Active Forum User
VOC Member
Basically this is no Ducati forum but even so I´d like to share my feelings about some problem spots: Oil quality is most likely not the biggest factor in roller big ends, though high viscosity helps a bit, in gear boxes too. But then warming up the engine is critical and no high speeds while cold are recommended, with single grade even more so.
Hardness of Duc conrod and crank pin are to specs , most Japanese singles got same type of conrods case hardened, be it SR 500, Honda radial four valve types etc. . A pressed in bearing race does nothing for ruggedness of the big end so I made my own conrods from chrome-nickel case hardening steel like these too. BUT big factor seems to be the bypass oil filter with the 860 and 900 cc Ducs so when dirt goes through the roller bearings in there all faces in conrod and crank pin will develop tiny surface defects that get worse in use and fail in 30 000km intervals . Later types had pins from 36 mm go to 38 mm and I believe the oil filter was changed to full flow, cannot tell. Even later types and all belt types got plain bearing cranks to cure this trouble spot - but got other worries - well, Ducati all the way.
Don´t know about crowded needle bearing in Duc gearboxes, basically this is a very high load design and used in many car gearboxes too. I was thinking the stuck 4th gear my friend Max had in Finland was due to running a steel gear on a steel shaft direct, no bushes there. But then, same type in Vincent gearboxes, needs decent clearance I suppose ? A good idea is to fit drain plugs with neodym magnets in all suitable places, takes out amazing wear deposits at no cost - and is a diagnose feature as well.

Vic
home made Vincent conrods with INA 40-48-20 mm bearing
P1050474.JPG
 

Pushrod Twin

Well Known and Active Forum User
VOC Member
If you are really interested i have a Vincati for sale in touring trim, and the way our Aussie Peso is going it could be cheap. PM me if interested.
Nice offer Chris, do you have to remove all of the asbestos components to export it as you would if you imported it? We feel it's only fair that under the International Asbestos Trading Agreement that Australia keeps it's share of the asbestos which it mined and kept in country seeing as it no longer accepts returns on asbestos it exported around the world for so many years. :p
Now, political pith taking aside, how would you like to give us some technical detail, please?
I would like to know how the rear of the engine fits into the frame, has the swing arm been connected to the rear of the crankcases?
 
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