Hmmm, erstwhile, huh? Good job I have my Funk and Wagnells handy!When I was tootling along behind you at 60 per the other weekend there was the merest drool of emulsified oleaginous liquid at your breather extension accompanied by a pleasant evanescent vapour. I remarked on this at the time. I think that 80 per is just not allowing the oil to separate and obey gravity, i.e.not enough height or bore diameter just past your P.C.V./P.E.I. valve.Perhaps you need a Reagan-type "trickle -down"solution rather than a leak-down test.Maybe you need a bigger bore all the way to, and just past, the valve aforementioned. I await stern correction as always.
Comet Oil Use
- Thread starter Martyn Goodwin
- Start date
follows my line of thinking. My immediate plan is to replace the breather hose with one of greater bore size in the hope it will reduce the velocity of the escaping gasses n oil mix thus giving the oil a chance to separate and return to the motor by way of the breather outlet.
I think it would be best if your erstwhile friend was Rex Bunn. His book on motorcycle breathers is too expensive for me to buy, but I have been lucky enough not to be plagued with heavy breathing. I agree that lowering the velocity is a good way to divorce your oil from its flighty partner. I am still concerned that regardless of the velocity you end up choosing for your crank case gases, that you have too many of them in the first place. Also, my telltale brain says that the breather should be able to relax and goof-off the higher the RPM. Certainly, the blow-by is much less the the higher the RPM due to much higher ring pressures, unless...
David
David
Thought time .... Is it blowby or just the pumping action? Have you (or previous owner) removed the breather pinion and shaft? Have you noticed where oil is thrown as it leaves the large idler and dynamo pinion? What happens if you throw large quantities of oil at a hole and blow 500 cc of air at it several times a minute? Too late in the day for me to think this through, someone else can have a sleepless night.
My PCV has no non return valve, but it does have a drain tube that I connect to where the valve lifter cable should go. I back it up with a non return valve in the pipe near the back of the bike and no oil comes out.
H
My PCV has no non return valve, but it does have a drain tube that I connect to where the valve lifter cable should go. I back it up with a non return valve in the pipe near the back of the bike and no oil comes out.
H
Hi David, I actually am using a "Bunn" valve on my Comet already. The original breather shaft is in place but the breather pinion is absent. I have fitted a banjo where the original breather pipe fitted on the left side of the motor and have a hose running up under the tank. At the highest point in the hose is the one "BUNN" valve. From the BUNN valve I then have a longish hose that finally travels along the rear stand leg, exiting to atmosphere at the rear of the bike, behind the rear wheel. The hose exit position is such that any oil that gets through it to atmosphere does not land on any part of the bike. This is the ONLY breather I have installed.
I am thinking of some form of expansion chamber between the breather outlet on the motor and the BUNN valve to allow the oil to separate out asap. I should add that I have a spare used BUNN valve as well and it no longer works properly in that it no longer operates as a one way but in the meant-to-be closed direction it allows gas to flow, though slightly restricted - and yes I have cleaned it out. So I will also be checking the installed "BUNN" valve.
Personal issues mean I will not be able to get back to working on this till late next week. Will provide an update then
Martyn
Martyn,
I look forward to your progress. On the racer I used a 3" chamber where the generator would normally be. the tube then came out of the larger can. I hoped that this would slow down the oil. On the Flash I used the timed breather in the stock set-up. I had no issues so I concluded that the "can" was not necessary. On the current incarnation I use a small tube to a Ducati breather.
Just in case folks do not know, Bob Lamour in Ontario, Canada makes some nice parts. One of the items he makes is high flow banjo bolts which would certainly breathe better. He also makes hubs from 6061 with the metric bearings that Chankly likes so much. These are quite strong and the same price as the cast ones.
David
I look forward to your progress. On the racer I used a 3" chamber where the generator would normally be. the tube then came out of the larger can. I hoped that this would slow down the oil. On the Flash I used the timed breather in the stock set-up. I had no issues so I concluded that the "can" was not necessary. On the current incarnation I use a small tube to a Ducati breather.
Just in case folks do not know, Bob Lamour in Ontario, Canada makes some nice parts. One of the items he makes is high flow banjo bolts which would certainly breathe better. He also makes hubs from 6061 with the metric bearings that Chankly likes so much. These are quite strong and the same price as the cast ones.
David
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Hi Martin, I have ridden two renewed Vincent Comets for thousands of miles over the last 3 years. Both with stock, simple breather pipes. I don't think i have seen a single drop of oil out of either breather pipe.
I was concerned about the timing, so I fitted a hose to these breathers to blow thru ....fitted a timing wheel....set the breather timing per instructions on this goofy forum....sumpthin I don't normally do!
Maybe my 65MPH is not putting the engine to task, maybe 80mph is generating a lot of air flow. But I would check your breather timing, not a tick mark, but actual open/close and piston position.
Cheers
Craig
I was concerned about the timing, so I fitted a hose to these breathers to blow thru ....fitted a timing wheel....set the breather timing per instructions on this goofy forum....sumpthin I don't normally do!
Maybe my 65MPH is not putting the engine to task, maybe 80mph is generating a lot of air flow. But I would check your breather timing, not a tick mark, but actual open/close and piston position.
Cheers
Craig