more on breathers

b'knighted

Well Known and Active Forum User
VOC Member
The so called Mac Read valve, was originally thought out by Ivan Caffrey of the York section. Credit where it`s due, likewise the Dave Hills stand was the creation of Larry Honour of Liphook.
Sorry, I didn't realise that - Did the Ivan Caffrey version use a vertical stainless tube instead of the rubber tube, or was that a later incarnation?
 

b'knighted

Well Known and Active Forum User
VOC Member
I replied before I read on - The Kemp version seemed to end up with what appeared to be a used Brillo pad in the ATD cover clogged with emulsified oil. The one on Peters bike has a rubber exhaust from the separator chamber but I have often seen them used without.
 

bmetcalf

Well Known and Active Forum User
VOC Member
I hope you have photos of the test rig and onlookers' reactions and will post them.

I thought this was disproved a few years ago by the French letter test? I certainly found with my PCV valve that on starting the 'bag' inflated to a few 1000 cc and then stabilized since the crankcase is now below atmospheric and the valve is preventing the air return
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
When I first got my Comet the PO had removed the original timed breather, replacing it with a pipe sans valve to atmosphere from where the magneto should have been ( please do not ask how or why). After I reinstated the magneto and the generator I tried all sorts of contraptions in order to get to a oil tight motor and a breather that did not approximate a total loss system. I had excessive crankcase pressure and nothing I tried seemed to work. I tried elephant trunks, PCV valves, Bunn breathers and a hole lot more.

The solution was found after I destroyed a piston thru detonation. I fitted a new liner along with a new piston and rings (and sorted the carb and ignition). This eliminated all of the earlier "blow by" that was causing excessive crankcase pressure. At the same time I installed an original timed breather, modified as recommended by PEI - I opened up the "slot" in the pinion thus giving a longer duration when the breather was open. Being a Comet I have only one piston to worry about. I set the timing of the breather so it opens during the down stroke of the piston, and closes at 2 degrees After Bottom Dead Centre.

My timed breather outlet now goes into a catch tank (actually a discarded plastic drink bottle, painted black) and in over 2,000 miles of running there is around a teaspoon fool of creamy emulsion in the catch tank. Oil consumption is so low as to be un-measurable.

Just my experience
 

Peter Holmes

Well Known and Active Forum User
VOC Member
I know that the Harley Davidson marque comes in for a fair amount of derision in our circles, but some of their Vee twins dwarf our meager 1000cc so they must be displacing a huge amount of air, what is the HD solution, most of the modern ones seem to be oil-tight without marking their territory whenever they park up.
 

Black Flash

Well Known and Active Forum User
VOC Member
Bloody hell Peter,
I know you well enough and seen your beautiful shadow to come along. But I have never ever seen your Rapide in such a shiny condition before.
If you find the time to polish your Rapide like that I think your not giving it all at redecorating the house ;-)
What a show off

Bernd
 

macvette

Well Known and Active Forum User
Non-VOC Member
Open Series D, engine rebuilt four years ago an now well run in. Standard D breather with outlet routed to an aluminium pedal bike drink bottle mounted on near side of the battery carrier. The outlet from the front exhaust cap is piped to a dip tube which ends just above the the bottom of the bottle and there is a short vent pipe from the top of the bottle. I put a couple of inches of oil in the bottle to create a liquid seal so it's easier for crankcase pressure to get out but needs about 4 ins of vacuum before outside air can get into the crankcase. The set up looks standard except for the bottle which fortunately came finished black so it doesn't stand out. The engine has inlet valve seals and when it's running you can feel a slight pulse of air from the vent tube on the bottle but no oil comes out. The oil level in the bottle barely changes in a years riding and the engine doesn't drip ( there is the occasional smear of oil around the rocker oil pipes). This is probably due to a very careful rebuild as well as the breather arrangement .
 

A_HRD

Well Known and Active Forum User
VOC Member
Bloody hell Peter,
I know you well enough and seen your beautiful shadow to come along. But I have never ever seen your Rapide in such a shiny condition before.
If you find the time to polish your Rapide like that I think your not giving it all at redecorating the house ;-)
What a show off

Bernd

Fear not Bernie, the photos were taken in 2007 - the last time it was polished properly. The photos show both sides of the pig-ugly and wonderful Mac Read/Ivan Caffery breather. I can ride 200 motorway miles and not have a drip under the bike at the coffee stop. All leaks are inwards!!! Now get back to work, you're not retired yet. ;)

Peter B
Bristol, UK.
 

paulpackman

Forum User
VOC Member
I have dug a few sketches I made from which I manufactured the breather valve that I have had on the Twin for the past 23 years.
Simon. If you have the facilities to do a bit of turning and if you give me your E mail address I will forward copies to you from which
you can manufacture same. I have attached a picture of my bike which shows the finished article in place which you may agree is quite neat.
IMG_0666.jpg
 
Top