new 850 MkII owner :)

This is the first bike I have ever owned, so naturally Im going to have some questions. I pretty young (26) compared to most commando owners but am a experienced mechanic with time in military aircraft engines, and personal race car (which I parted out to buy the bike) The bike has about 17k on it, and sat since 1985 inside someones house as "art". Overall its in good condition, needing the normal items replaced and such. I took the bike out for its first ride recently, and noticed some oil leakage, which I expected. Today I decided to take it out for alittle longer, to pinpoint the problem. It seems to be puking a pretty good amount of oil from the oil tank breather hose, and possibly from the cap. I tried doing some searching on here, but my lack of bike experience is the problem. The hose is vented to atomsphere, hence oil being everywhere. Is this due to the bike sitting for quite a long period of time, and the engine needs to be run to get everything sealing correctly again, or do I have a much larger issue on my hands? The bike fires up 1st or 2nd kick everytime, so Im thinking the engine is in solid shape.

Double check oil level and then breather issues. You can search here for extensive knowledge on both issues.

By chance did you check the oil tank, find it low, and add oil? 'Cause if you did that on a cold engine, the sump may have been full of oil that returned to the tank when the engine started, and you're running with an overfilled oil tank.

That was something i was thinking. I checked the oil level when it was hot and found it to be over the full line. I didnt have time to let everything cool down enough to check the oil again. Ill give that a try tomorrow, and see what comes up.

Nice to see the youth of today has taste.
I would remove the plug from under the engine, and drain the oil from the engine.
Then remove the oil tank plug and drain the tank, and also I would change the spin on filter cartridge located in front of the rear wheel. I think you will have one of these, a MK2A?
Fill it with either straight 40, or 50 or I use Duckams green mineral oil 20/50.
No doubt others will comment...
Change the oil regularly on these bikes, they need it. I go for about 2000 mile intervals, but I only do the cartridge every other time...
Keep the oil level at the bottom level to just on the stick, never go to top level, it will just burn it otherwise.
They \wet sump easy, maybe after two weeks standing you can loose a pint in the engine, so be carefull not to top up ontop of this as previously suggested.
Always use the kickstart to pop the jugs onto top dead centre after riding, this slows down wet sumping.
Welcome to Commando ownership, I love mine! (850 mk2a
Stu.

Duckams maybe a bit hard to find in Pennsylvania. As for oil readily available here in the states, use something with a high zinc content. Redline and Torco both have a high zinc content. Mobil 1 is hard on Norton camshafts. This I know from personal experience and verified by the owner of Web Camshafts. As for not changing the filter with every oil change, you are leaving quite a bit of dirty oil in the system. Kind of like washing your feet and putting on your dirty socks back on. Besides, we're talking saving less than $10. If it we're me, I'd route the crankcase vent hose back to it's original position, the oil tank. The tank should be vented to atmosphere, usually the air intake box. I'd also recommend a crankcase breather check valve inline. Once installed, a lot of oil leaks mysteriously disappear.

Great to see a young rider who appreciates old British iron. Good luck and check in here often.

The breather hose you are referring to is a second breather hose from the oil tank. Originally it was connected to the back side of the air cleaner, aka as the 'ham can'. Engine vacuum burned off the mist.
The primary engine breather is connected to the oil tank, which in turn pressurizes it.
If the oil tank is too full it will puke oil out that second breather.
All normal. Test it yourself. Pull the oil cap while the engine is running. You'll get the idea.
The oil level needs to be measured when HOT, not COLD. As mentioned it needs to be at the bottom of the stick.
Are you familiar with 'Wet sumping'?
The oil drains/weeps/ from the tank to the bottom of the engine when it is sitting. After awhile you check the oil tank and say OMG, there is no oil and add some. After the engine is started it pumps it back to the tank and out the second breather if it is too full. Now you have a nice, well oil machine....everywhere. Sometimes it pumps it up through the rings, causing smoke, giving a false impression of a bad engine.
There is alot of info here and everywhere regarding cures.
The easy one is too check the oil tank, if it is empty, drain the engine sump and pour back into the tank.
Sounds like a pain, but you'll get good at it.
You can also attach a puke bottle to the second hose to catch the mist.
Welcome to the world of Commandos. 8)

Vulin said:

I pretty young (26) compared to most commando owners ...

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Welcome aboard. I'm a 26 year old Norton owner myself - just getting started on a restoration of a '74

Post pics!!!

nomadwarmachine said:

Post pics!!!

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lol.....yeah, I wish every topic had pics!!

Here are 3 quick recent shots from today. The bike may cream at first, but was painted red. My plan is to redo the tank, get the front fender stripped and back to its chrome form, and a couple other cosmetic things.

Vulin said:

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You're hurting the seat!

haha well possibly a corbin seat will be coming along sometime in the near future. Im about 6'5 255ish, so im sure the rear suspension isnt to happy either.