55,000 miles on a 47 Vincent

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worntorn

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I've caned this bike hard for much of the riding so it wasn't a big surprise when noticeable compression loss showed up about 5,000 miles ago.
The expectation was to do a top end rebuild this winter. That should see the engine thru to 100,000 at which point the bottom end will likely need renewing.
Although maybe not!
What I found at 55,000 was rather surprising. The valve stem wear measures just 2 ten thousandths, of an inch. Really just a nice polish in the guide areas.
The cylinders are perfect, no scoring and zero ridge at top. Will measure for wear and ovality tomorrow. I suspect they will be fine.
The rocker bearings ( duraluminium) show no visible play, so as new.
The valve guide clearances all measure well within normal spec, again very close to new numbers.
The compression loss was due to some pitting of the valve seats and crud on the exhaust seats. That all cleaned up with lapping compound, valves are gas tight again.
I bought some new valves thinking the 55,000 mile ones would be toast, but they are in great shape and back in.

I don't know if I will live long enough to ever wear this thing out!

Glen

 
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There may be a bit of richness somewhere in the throttle opening range, causing coke to stick to the exhaust valve seats.

Worn needle jets?
 
Triton Thrasher said:
There may be a bit of richness somewhere in the throttle opening range, causing coke to stick to the exhaust valve seats.

Worn needle jets?
Click to expand...

Could be.
For about 45,000 of the 55,000 the bike had very old Concentric carbs in place.
They worked perfectly for most of that, but did cause the bike to run very rich when the needle jets wore out. By then the slides were well worn out too, so new Premieres went on.
Fuel mileage with the old Concentrics was around 50 mpg most of time. It dropped to as low as 30 when the needle jets wore out.
With the Premieres fitted it's getting 55 mpg.
For 55,000 miles travelled there isn't a lot of coke on the cc or piston tops.

Glen
 
The bike is fairly stock isn’t it Glen?

If so it’s incredible to read your words and think about what ANY other bike made in 1947 would be like at that mileage!

Respect to the Phil’s !
 
Yes, close to stock.
Ive really hammered on it. For some reason it is a real rocket.
At the IOM I came onto the Sulby straight and saw five Vincent twins doing over the ton , all with riders laid flat on the tank. Well out In the lead was a beautiful Black Shadow that had been restored by Patrick Godet.
The rider was a hard riding young French fellow who had passed me as well as many others earlier.
I managed to get by the whole lot.
After that I rewarded it with 2500 miles of two up touring in the UK.
Other times it's done tons of mountain riding, often wot in 3rd for miles hauling up some big grade, two up with luggage at 80-90 mph.

We recently had a thread about testing Commando oil pumps for flow to avoid catastrophe.
I swear this Vincent oil pump, like all of them, oozes out about 20 drops per minute.
Somehow it all works.

Glen
 
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Soot can burn off from the piston crowns and cylinder head surface, but I think it can somehow glaze onto the exhaust valve sealing face and eat into the valve.
I cannot explain the physics/chemistry and I could even be wrong (again), but something like that seemed to happen to my T110.
 
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VR1 20/50 most of the time.
After seeing Jim's tests I'm switching to Belray.
VR1 tested fairly well but BelRay was better.

Glen
 
Triton Thrasher said:
Soot can burn off from the piston crowns and cylinder head surface, but I think it can somehow glaze onto the exhaust valve sealing face and eat into the valve.
I cannot explain the physics and I could even be wrong (again), but something like that seemed to happen to my T110.
Click to expand...

That would explain it.
From memory, the trip where the mileage dropped dramatically due to worn needle jets was also the trip where the compression dropped off.

Glen
 
I once got about 50,000 miles out of a T110 top end, but the state of the valves, guides and seats indicated that I should have overhauled it long before that.
 
With an old ring pushed down and squared up by bumping with piston, end gap measures 2 thou max variation top to bottom on one cylinder, 3 thou the other.
So dividing by Pi, both are under 1 thou taper.

Glen
 
I found another problem, the front cylinder exhaust valve lower guide was very loose in it's pocket. It appears to have been moving up and down & all around with the valve for many thousands of miles.
The seat was also a bit banged up from this. Luckily, Vincents also have an upper guide so that got tested.

The fix was to bore the egg shaped guide hole back to round and also considerable oversize on the Monarch lathe. I then made a new oversized valve guide in 660 Bronze.
After shrinking that into the head it was line reamed to 2 thou clearance on the valve.

I ground the seat using a borrowed 1960s Black and Decker unit.
No fancy three or five angle grind, just one angle as per stock Vincent (30 degrees) At 5500 rpm max I don't think the number of grind angles matter much.

With a minimal lap after the valve was gas tight.

I've got the engine back together and nearly ready to go.
The compression is back, the kicker will hold my weight for 10 seconds or so.
This motor might make a bit less clatter now.

Glen
 
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All together now and roadtested. The engine is quieter by half but still makes a fair old Vincent clatter.
It runs a little stronger showing 72 mph in top Gear at the top of dyno hill. It feels a bit sharper on roll on too.
Speed with the leaky valves was down to 68 mph at top of hill.
Not the difference one might expect going from an easy push thru compression to stand on the kickstart compression.
I suspect that the difference here is the static to dynamic difference.
When the valves are slamming shut while running the leakage is likely much less than felt at kickover.
Still, dropping from 70 at bottom to 68 at top vs pulling up from 70 to 72 at top is a nice increase, maybe 4 or 5 bhp?
The main thing is that the front cylinder exhaust valve lower guide is actually doing its job now!


Glen
 
worntorn said:
I suspect that the difference here is the static to dynamic difference.
Click to expand...
I think you are correct. My ES2 for once had a problem with the exhaust valve, it would tighten up on any decent run. Once after a lunch stop there was no resistance on the kick start lever but some dodgy people were hanging around us so i tried starting it and after a couple of firm kicks rode off - and adjusted the clearance down the road a bit.
 
That is quite a testimonial in several ways:

-The Vincent itself (design & robustness)
-Owner knowing how to ride hard without abusing the machine
-Quality of lubricants employed
-Value of regular/proper maintenance
 
Thank you for sharing this.
I know I want one.
I try to avert my eyes, thinking I can keep the “must find one” train from leaving the station in my mind...
 
Vincent was the motorcycle of our dreams when we were young. They were legends... Only knew their beauty and now I find they are amazingly hardy and reliable. All I've known them from is pics, much less heard one run.
 

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