Drip from Breather

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Hi all,
I believe my very stock 74 Mk2 850 to be in excellent mechanical condition, other than a high idle issue when hot that I posted about previously that I’m still investigating.
It is very oil tight
the breather from the oil tank is routed along the RH swing arm before venting to the atmosphere. Is this the original arrangement or did it vent into the air cleaner housing?
When parked there is always a small puddle of frothed oil from the breather.
It doesn’t really worry me but is this normal
al
 

Nater_Potater

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There's been a number of comments made here about the possibility of mis-marked dipsticks goading you into running the oil too high. I can't quote them directly (too lazy to look up right now). I know my '74 will do that if running at the "Full" mark, so I keep mine at the lower mark. Not to sound condescending, but did you make sure to run the engine sufficiently before checking the oil level? As you may know, if you were to top up the tank without doing so, then the oil that's hiding in the crankcase gets pumped on top of the already full tank, thus leading to an overfull situation.
 

MichaelB

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Yes normal. It originally vented to the air cleaner.
 
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Hi
There's been a number of comments made here about the possibility of mis-marked dipsticks goading you into running the oil too high. I can't quote them directly (too lazy to look up right now). I know my '74 will do that if running at the "Full" mark, so I keep mine at the lower mark. Not to sound condescending, but did you make sure to run the engine sufficiently before checking the oil level? As you may know, if you were to top up the tank without doing so, then the oil that's hiding in the crankcase gets pumped on top of the already full tank, thus leading to an overfull situation.
Nater
Thank you for the reply. Yes, I’m very aware of the wet-sumpimg issue The oil is checked after the motor has run for a little while. The oil level is certainly up to the full mark which I guess is where I keep it by default, not that it uses significantly oil.
The dipstick looks correct with actual level well below the filler neck of the tank.
The small amount of oil that drips out surprises me a little but is not a problem.
I don’t like the idea of returning it back to the inlet for fear of gumming up the paper air filter, although now I have changed to a K&N foam element so I suppose it doesn’t matter
On another matter, am I the only one driven nuts by the exposed air cleaner and the issue of soaking the element through the perforated housing when washing the bike?
The good news is that the bike is just getting better and better as is my enjoyment riding her. Unfortunately, to quote Game of Thrones ‘Winter is Coming’ which will curtail much riding.
Al
 

maylar

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When my Commando was only a couple months old it started having power issues going uphill. Worse in higher gears, worse with a pillion. As it was still in warrantee I brought it to my dealer who did a "tune up". It came back with the same problem. Then I noticed oil dripping from the air filter. I had over filled the tank and the filter was saturated. Installed a new filter and problem solved. That was the last time the dealer ever did service on my bike.

The rider's manual mentions this - to run the engine for 3 minutes before checking the oil level. I keep mine between the 2 lines on the dip stick.
 
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On my MK2A filling to the H mark will cause the breather from the tank to the air filter to deposit too much oil, so I fill to half way between H and L after the engine has been run to drain the sump and the air filter is moist but not wet with oil. As its a foam filter on the MK2A that works well.
 

jaydee75

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Hi all,
I believe my very stock 74 Mk2 850 to be in excellent mechanical condition, other than a high idle issue when hot that I posted about previously that I’m still investigating.
It is very oil tight
the breather from the oil tank is routed along the RH swing arm before venting to the atmosphere. Is this the original arrangement or did it vent into the air cleaner housing?
When parked there is always a small puddle of frothed oil from the breather.
It doesn’t really worry me but is this normal
al
Me too, that's the only drip I get off of my bike......I'm happy.
Jaydee
 
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I also run an open vent since 1978. I might get a small drop from the hose when I shut the engine off after a run.
 
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On another matter, am I the only one driven nuts by the exposed air cleaner and the issue of soaking the element through the perforated housing when washing the bike?
Don't spray the air cleaner with water. Problem solved. Errant water won't affect it.
 

Tornado

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My 74 MK2 850 has the stock. Breather running to tank, then tank to air filter back plate. Ive fitted the Yamaha reed valve to the breather from the timing chest.
One sunny day while checking for oil leaks, idling on SS, I noted what looked like smoke puffing out the K&N air filter. Blipping throttle sucked it straight back into filter, idle would see faint puffs emerging. Turned out to be oil mist, not combustion exhaust.
I think the reed flapper tends to aerosolize any of the hot oil vapour condensing within.
Does not worry me.
Some folks run catch cans, steel wool within, to help cool the breather oil vapour and reduce any venting to environment.
 

MichaelB

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I have a catch bottle in the battery tray.
Since installing the NYC/Comstock sump breather, bottle stays relatively dry.
Been considering cycling it back through the air cleaner.
 

lazyeye6

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My oil tank vent still goes to the air filter back plate even though I have a Mikuni with a pancake air filter. Never had a drip or even any
Milky splooge. Perhaps some very light vapor. I have a Comstock sump reed valve breather and never fill my oil tank higher than half way between the high and low marks on the dip stick. I also don’t allow wet sumping by using a oil supply valve WITH AN IGNITION INTERLINK.
 
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Hi a

hi all,
well that all sounds pretty simple, I’ll just run with a bit less oil in the tank.
And I still don’t like an air filter that can get waterlogged from a simple hose down

al
I've never hosed down my Norton.
Only wipe it down , with soft rags or shop towels.
Water gets into electrical connectors etc. and oxidizes them.
For the past few years I've decided to never drive it in the rain too.
That's 2 nevers.
When I was young these nevers were ignored.
 
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Y'all use water on your Commando? For mud on the tires, guards and wheels I understand, but all else I use a spray/squirt solution and wipe with clean damp cloth. Apply polish or wax after if needs be.....never a pressure wash unless totally rebuilding something... Compressed air comes in handy in my rare cleaning escapades also...... I guess I just think differently.

Rain is no no for me also..... don't carry rain gear plus no faring.... I'm spoiled and like my Commando dry. She's too old for BS riding and of proven worth already in my eyes.
 

illf8ed

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Hi all,
I believe my very stock 74 Mk2 850 to be in excellent mechanical condition, other than a high idle issue when hot that I posted about previously that I’m still investigating.
It is very oil tight
the breather from the oil tank is routed along the RH swing arm before venting to the atmosphere. Is this the original arrangement or did it vent into the air cleaner housing?
When parked there is always a small puddle of frothed oil from the breather.
It doesn’t really worry me but is this normal
al
Hi Alan, Idle going up when the engine gets hot issue has been around for several decades. It’s air leaking past the carb slides. Amal bodies get out of round easily when the flanges are over tightened to the intake manifolds. The slides wear uneven allowing air past. In the past we sleeved the slides, trued and bored the bodies. May be easier to buy new Amal Premiers these days.
 
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