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A: Oil Pipework Oil consumption

robin stafford

Website User
VOC Member
Has any body checked the oil used on their twin . I have no oil leaks apart from the crank case breather to which has been extended to the rear pillion foot rest hanger cannot seem to seem to stop oil from leaking out when stopped about 1 inch dia puddle on the road. I have routed the breather pipe under the engine. would it be better to go upwards with the breather pipe but the route would not be easy . For the last 5000 miles i have been using fully synthetic mobile one 0/30 with the high content of ZDDP with no restrictors in the barrel feeds and no metering wires in the rocker feeds. no smoking on the over run or normal running . would you say that 500 miles per pint is ok . I think most of the loss is going on the road via the breather any ideas
 

Albervin

Well Known and Active Website User
VOC Member
I usually obtain about 3,000 miles with no loss of oil that I can measure. I use a 30/50 oil with lots of zinc and phosphorous etc. I change oil at 3,000 miles or twice a year (Summer/Winter). In Australia, Winter and Spring are best riding times. If you are using the standard timed breather it has been well documented to enlarge the slot to extend the timing. When was the engine rebuilt? How many miles on the rebuild. After a rebuild I will put the ugly elephant's trunk on for a couple of thousand miles and then re-fit the original breather but with a wider slot. The only oil leak I have is the two drops under the crankshaft sprocket which annoys the hell out of me. Originally Vincent said about 200 miles/pint which is beyond belief. Later it was amended to 500 miles. Today, with modern metallurgy and machining I would expect nothing less than 2,000 miles/pint. If you are not burning it then there is a serious problem with breathing. Co-incidentally I was only talking to someone an hour ago who was losing a lot of oil via the primary drive/generator. He drained over a litre of oil from the primary drive and his rear tyre was soaked. In the twenty years since I rebuilt my Rapide it has consistently never needed an oil top up between oil changes.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
If its blowing out the breather then the crankcases are getting pressurised from blowby past the pistons and rings. There is no shortcut to dealing with Vincent barrels and excessive oil consumption and you have to ensure the fit between muff and liner is correct before anything else and simply boring a barrel to say +20 piston will not work.
A Vincent with modern pistons, rings and properly sorted barrels should do at least 2000 miles per pint. I used to change the oil in my Rapide every 2000 miles and inbetween it didn't need topping up at all. Over the last couple of years that slowly got worst and started to blow oil out of the breather, but didn't appear to be burning oil. So last year during to lockdown I pulled the top end and found the front cylinder liner had lost its interference fit so it was time to do a top end overhall as the pistons and liners had been in for over 50,000 miles. New pistons, new liners in the muffs which was bored to 6 thou interference fit to the new oversized liners, and its back to a clean breather pipe but I have not managed to do many miles to fully bed the rings in due to covid restrictions and winter.
 

robin stafford

Website User
VOC Member
the engine has been built four years ago with new voc barrels and new 7.3 pistons new valves and guides but has some mk2 cams so the guides are machined down with no seals . the engine does not sump even after a month . in four years only had to drain a egg cup full of oil out of the chain case .may be the oil is a bit on the thin side but it makes it very easy to start even in this cold weather, starts 1st or second kick
 

Ken Tidswell

Well Known and Active Website User
VOC Member
I wonder if the bore has glazed over before the rings could settle in.
I think you have got glazd bores . Does the oil smell of petrol? I f that is the case then change to a running in oil for 200 miles drain and fill up with a 'Classic ' oil of which viscosity you prefer. IMHO modern high lubricity oil can be a problem with older engines with ring packs not degsigned to work with synthetic oil . This happened to a Comet of mine.
 

greg brillus

Well Known and Active Website User
VOC Member
I would say the bike sounds perfectly normal.......especially using that thin an engine oil. The bikes sent out new from the factory would have used oil on account of the oil passage through the liner being too high up and delivering oil into the rings. Nowadays everyone's expectations are that of the modern car/bike that it should be oil tight no matter what.........well to find a perfectly oil tight Vincent is extremely rare.......no matter how well built it is. Probably better if you change to the "D" type breather cap over the front exhaust valve, and blank off the original spot with a new sump drain plug and sealing washer......Run this pipe aft and down forward of the battery box, and "T" it together with another short flexible pipe to the oil tank breather line, then run this with a length of 3/8" bore black oil hose just aft of the rear axle on the left side of the machine. If the engine starts quite easily now, I would go to a higher viscosity oil........If the drive side main bearing is a standard open type it will loose some oil into the primary, this is normal, but just drain off the excess every so often. If the primary level comes up say a 1/2" more than the drain plug height, it will tend to loose some oil out from where the generator passes into the top of the primary housing.......Some folk go to all sorts of effort to seal the generator here, but I have found it not necessary.
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
I think the oil you are using is way to thin. I have been using Amsoil V twin 10w50 for a few years. I am not sure it is the best but it works. My bike uses so little oil I never have to add any. I have the standard breather with a pipe that goes back to almost the rear axle. Almost nothing comes out of there. Usually just a shot of emulsified oil when I kick the bike over. I use a non standard timing for the breather which makes a lot more sense than the standard timing. I believe it reduces the pressure in the crankcase. I am not the only one who does this. Recently I solved the oil consumption problem with my car a Merc SLK350 by chaging from a 0w-40 oil to a 10w-60 oil.
 

Nigel Spaxman

Well Known and Active Website User
VOC Member

LoneStar

Well Known and Active Website User
VOC Member
I found Nigel's dissertation very convincing, so adopted his ideas during my recent rebuild. I also replaced the banjo bolt with a L-fitting, for greater cross-section, and use thin-wall black tubing from there (c. 1/2" ID).

Good results, not perfect. A few drops of oil escape from the tube when idling or parking after a ride, but very little. No accumulation towards the rear of the bike, and very little overall oil loss.
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
I found Nigel's dissertation very convincing, so adopted his ideas during my recent rebuild. I also replaced the banjo bolt with a L-fitting, for greater cross-section, and use thin-wall black tubing from there (c. 1/2" ID).

Good results, not perfect. A few drops of oil escape from the tube when idling or parking after a ride, but very little. No accumulation towards the rear of the bike, and very little overall oil loss.
I use the standard Banjo bolt but I drilled it out a bit, and I marked it to make sure the hole is always lined up with the tube. I have a 3/8" tube, a pretty standard one going under the engine, a hose going back to near the swing arm, and then a tube attached to the brake stay. Not much leaks out. I am glad to hear that some other people read about my method that and are using it. A lot of people just can't get past the idea that the valve has to be open only when the pistons are coming down. It has more to due with the crankcase volume than what direction the pistons are moving. The standard timing closes the valve right at the exact time when it should remain open for a bit longer.
 

robin stafford

Website User
VOC Member
I have checked the engine oil no smell of petrol so I dont think the bores are glazed the compression is very good can stand on kick start with both cylinders. will using mk two cams increase the oil consumption with short guides. I have got an elephant trunk breather may try to see what happens but I dont like the look of them . What is the theory of using thicker oil it take longer to reach the cam gear. 5000 miles I have only adjusted the valve gear once on the front exhaust Have done oil temp checks in the summer after a 100 mile run at 60/80 mph the most recorded was 36 c so a thicker oil will never come up to its working temp
 

LoneStar

Well Known and Active Website User
VOC Member
I use the standard Banjo bolt but I drilled it out a bit, and I marked it to make sure the hole is always lined up with the tube. I have a 3/8" tube, a pretty standard one going under the engine, a hose going back to near the swing arm, and then a tube attached to the brake stay. Not much leaks out. I am glad to hear that some other people read about my method that and are using it. A lot of people just can't get past the idea that the valve has to be open only when the pistons are coming down. It has more to due with the crankcase volume than what direction the pistons are moving. The standard timing closes the valve right at the exact time when it should remain open for a bit longer.
FWIW, here are the measurements I took of my stock breather installation. Cross-sectional area at various points, in square inches:

1. slot in breather collar - .252
2. slot in breather spindle - .179
3. breather spindle bore - .085
4. bore, banjo bolt - .054
5. side holes (4) in banjo bolt, total - .076
6. annular gap between banjo bolt and ring - .085
7. output pipe from banjo ring - .041
 

bmetcalf

Well Known and Active Website User
VOC Member
I have checked the engine oil no smell of petrol so I dont think the bores are glazed the compression is very good can stand on kick start with both cylinders. will using mk two cams increase the oil consumption with short guides. I have got an elephant trunk breather may try to see what happens but I dont like the look of them . What is the theory of using thicker oil it take longer to reach the cam gear. 5000 miles I have only adjusted the valve gear once on the front exhaust Have done oil temp checks in the summer after a 100 mile run at 60/80 mph the most recorded was 36 c so a thicker oil will never come up to its working temp
ClevTrev has reported low temperatures after a longer run. I can’t remember what weight he recommends, but it seems logical to experiment and get the temp up to 180F by using lighter oils.
 

LoneStar

Well Known and Active Website User
VOC Member
ClevTrev has reported low temperatures after a longer run. I can’t remember what weight he recommends, but it seems logical to experiment and get the temp up to 180F by using lighter oils.
Apologies if this is obvious or universally understood - but why would a lower viscosity oil run hotter, other factors being equal?
 

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