Is there any advantage whatsoever in using upper cylinder lubricants such as Redex (if it still exists) or a dribble of top quality 2T oil, I know that would not cure piston expansion beyond the bore diameter, but would it help in marginal cases.
E: Engine Partial Single Seizure? Safe to ride?
- Thread starter CoreyL
- Start date
That's why the boys in "the know" use a bit of synthetic in the oil until normal running in cures the nipping, as I suggested. I'm well aware it isn't best engineering practice but it can save a lot of work. If it nips a second time (and you should catch it immediately) then you will have to hone it out a bit.
Just to cheer you up I will tell you the story of my nip up on the Knight. This was in the mid to late 1960s and I was happily blatting up the M1 on my way to Yorkshire to see my family when the nip up occurred. I managed to get the clutch in and cruise from the outer lane to the inner lane and pull up. The engine turned on the kick starter so I slowly went up to the next pull off, stopped and tried the compression. It seemed OK so I decided to try to get to the next junction and so proceeded all the way to Wakefield. Once there I took out the spark plugs and put a small screw driver down the plug holes and felt around. This was long before fibre optic probes etc. I could not feel any indentations etc. so decided that I might as well see if I could get back down to the south coast where I was working. No problems. I then drove down to Paris, picked up a young lady and then continued on to the South of France for a camping holiday with said young lady and all the camping gear on board. Two weeks there and then back with no problems. I continued to use the bike for years and when I did have a look inside the heads the only sign of the nip up was an 'orange peel' finish to the top of one of the pistons. This was all long before I knew that the Knight was the prototype and I had fitted an Avonaire fairing to the front of the bike and left the original Knight mudguard in place. Clearly there was not enough air flow round the engine with that combination and later I widened the hole in the front of the Avonaire to get more air round the engine. If there is a moral to this story it is that you might be lucky. If the compression is still good then treat it gently for a few miles and if it is still OK then keep using it. If you are sensitive to engines then it will let you know if it is unhappy and struggling and if it does then just be thankful that you have a Vincent and it is so easy to take the front end and heads off when one has to.
When I was young and very new to Vincent engines I started racing the Norvin I had built at the Silverstone High Speed Trials having done many road miles over the previous three years. I had previously noticed one of liners tended to tended to rotate so just put in a small dowel to prevent the oil hole from being blocked. Silverstone in those days was always in June and a high-speed, lots of full throttle circuit. The heat generated caused it to nip up on the straight at one meeting but by the time I had slowed, it had freed up and I dropped the clutch and off I went again. I just increased the main jet size and finished the meeting. Subsequent investigation, by immersing the barrels in boiling water, showed both liners had virtually no interference when hot and then only in places. No wonder they seized in a half-hour High Speed Trial. The extra heat had nowhere to Go. Skimming the muffs and oversize liners with 6 thou interference was the cure. Why the original interference had disappeared is a mystery, they were not the die-cast ones. Maybe it just wasn't there in the first place.
Well, I typed this last night but forgot to send 
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After a bad seizure you can expect the piston to be a LOT smaller in diameter than before. It is sort of heat treatment in these marks and the Jag pistons were about 10 or 20 thou smaller , rattled a bit when cold but we could drive home no problems at all another 300 km, no ugly noises when hot.
As to seizures, in case the seized cylinder from CoreyL gets inspected, I´d be very interested in seeing all of the bore plus piston. For checking geometrical roundness, set the cylinder on a mill and use a clock in the spindle rotated by hand . That should show any defects in roundness all along the liner down to the part that goes into the crank case. Still I suspect poorly honed liners, producing regular marks as in the Jag examples. Also, I would not exclude deformations when pushing liners into the crank case with slight force. I would not accept even minimal resistance when plunging them into the case for fear of deformation. You cannot be sure that case halves get mated perfectly with all those old position bushes in their (oversize?) bores after many decades of butchering.
So considering all possible flaws on aged Vincent components I would not dare to state causes for seizures without having measured all relevant components of that particular engine. It is too easy to draw wrong conclusions on hearsay.
Vic
:After a bad seizure you can expect the piston to be a LOT smaller in diameter than before. It is sort of heat treatment in these marks and the Jag pistons were about 10 or 20 thou smaller , rattled a bit when cold but we could drive home no problems at all another 300 km, no ugly noises when hot.
As to seizures, in case the seized cylinder from CoreyL gets inspected, I´d be very interested in seeing all of the bore plus piston. For checking geometrical roundness, set the cylinder on a mill and use a clock in the spindle rotated by hand . That should show any defects in roundness all along the liner down to the part that goes into the crank case. Still I suspect poorly honed liners, producing regular marks as in the Jag examples. Also, I would not exclude deformations when pushing liners into the crank case with slight force. I would not accept even minimal resistance when plunging them into the case for fear of deformation. You cannot be sure that case halves get mated perfectly with all those old position bushes in their (oversize?) bores after many decades of butchering.
So considering all possible flaws on aged Vincent components I would not dare to state causes for seizures without having measured all relevant components of that particular engine. It is too easy to draw wrong conclusions on hearsay.
Vic
Tony Maugham, and I would guess Steve and Graham used to say that after 50-60 years the cylinder muffs simply stretch until they have little or no interference fit left, they have simply expanded and shrunk to many times, Tony used to manufacture thick muffs to overcome the problem, I cannot comment on whether this solved the problem, but it seems likely that it would.