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Who makes this breather?

minivin

Well Known and Active Forum Website User
VOC Member
Ok, I have just looked at the bottom of the pannier that was on the left hand side of my Comet, and it is SOAKED with oil that must have come out of either the engine breather, or the clutch mainshaft hole.

To say that I am sick of this bloody Comet is now putting it exceedingly lightly. Three sodding rebuilds and the thing is pumping oil out of it faster than I'm putting petrol into it.

I never had this problem while running an Elephant trunk the first time round, but I just don't like the aesthetics of it. Could someone tell me who makes the following engine breather and whether it can be fitted with a straight Britax crashbar in the sidecar lug?



Having had the barrel rebored a second time with new pistons and suffering this problem again, I can only come to the conclusion that the standard breather channel is heavily restricted on my bike.
 

ogrilp400

Well Known and Active Forum Website User
VOC Member
Far too much emphasis is placed on breathers on Vincents. They are only meant to relieve a small amount of gases that bypasses the rings and exhaust guide, not 500cc every stroke as a lot think. The primary on a Comet (and a twin for that matter) only need a very small amount of oil and if that oil rises then it buckets out the clutch shaft hole. So, first a seal is needed on the crankshaft to stop oil migrating from the crank case into the primary. Next a felt and oil slinger is needed on the back of the clutch to make sure that no oil at all gets out.
 

minivin

Well Known and Active Forum Website User
VOC Member
Unfortunately I lost 1/2 litre of oil in 100 miles, I suspect therefore that I may have either of the following problems:

i) the crankcases are constipated
ii) the new oil pump is not scavenging correctly
iii) the new barrel and piston is duff
iv) the reconditioned head is duff

After re-timing the breather a second time, after the bike used to throw the oil out the exhaust port as well, the exhaust is still suffering some oil leakage as the mag cowl had a few splatters over it after the 100 miles, it was also kicking smoke out the exhaust at low speeds and primarily when opening the throttle. The breather was timed via the old method of blowing down the pipe till it opens at TDC and if I remember correctly, it closed at 20BBDC.

The new oil pump should work, but I may have to start pulling the sump plug after a run and seeing whether any oil comes out.

The barrel has a brand new liner in a Trevor Southwell muff, I also took Trevors recommendation of not even bothering with drilling the piston skirt oil gallery, so that oil path is no longer.

Finally the cylinder head is a more complex matter, a new inlet guide should have solved any induced oil consumption.


Having had items on this engine reconditioned for four rebuilds in five years, the only missing factor is that I no longer have an Elephant trunk on the bike.........
 

Hugo Myatt

Well Known and Active Forum Website User
VOC Member
I have had this type of breather on my Rapide for many Years. It was made by Ivan Caffery. It has never, as yet, passed any oil noticeably.The down side is that the nylon ball in the non-return valve adds considerably to the normal Vincent clatter. Some people say that the exposed stainless pipe causes condensation and consequently sludge in the system although I have not found this to be the case.

Regarding crash bar. Yes it can. When the Rap was solo I had a Maughan SS crashbar fitted along with the breather. Now with a sidecar it does not interfere with the fittings either.
 
Last edited:

vibrac

Well Known and Active Forum Website User
VOC Member
Far too much emphasis is placed on breathers on Vincents. They are only meant to relieve a small amount of gases that bypasses the rings and exhaust guide, not 500cc every stroke as a lot think. .

Yes 4 quid for a standard motor parts PCV in line filter and the jobs done -perhaps 2 for a big twin.
Its all here discussed a thousand times use the search button top right :-0
 

timetraveller

Well Known and Active Forum Website User
VOC Member
" till it opens at TDC and if I remember correctly, it closed at 20BBDC" !! Does that mean that the breather is open all the time the piston is descending and closed all the time it is rising? If so then look no further.
 

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
Another wrinkle I discovered is a variation in the boring/casting of the exhaust port and neighbouring rocker tunnel. My Comet had the tunnels re-bushed, and the engineer did this beautifully- but just broke in to the exhaust port by a freep. This took some time to track down and bugger-all time to fix! It produced similar symptoms to yours. Are you sure the breather is timed right- read my previous posts and more erudite ones as well! Failing this, have you got a porous casting? Keep us informed and please don't lose heart!Cheers, F5AB/2A/7945 since 1970. Less than Half a litre in 500 miles. Kemp piston, standard breather, valve stem seals.
 

john998

Well Known and Active Forum Website User
VOC Member
Yes it was made by Ivan Caffery, some years ago. Ivan is not too well at the moment sadly.
When one was fitted to my Rapide the oil consultation dropped by half, only disadvantage is the noise from the nylon ball clacking. John.
 
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