Engine Breather Hose Size

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Rondo

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Almost embarrassed to ask this one, but the bike was purchased without some of the oil hose components on it so I didn't have the advantage of seeing how it is done properly. 1975 850 commando, the breather port coming off the back of the engine timing case is about 1/2" in diameter, the port on the oil tank just under the fill cap is only about 3/8"? What the heck? Do you go with 1/2" ID and then just cinch it down tight with a clamp on the oil tank, install a reducer?

So simple but just wondering what is normally done.
 
oil tanks 3/8 filler neck breather sounds like early, which do you have?
73=06-3095
74=06-3975

75 oil tank 06-3456 1/2 at filler neck
If all else fails you can get a 200K combat style reducer
 
This bike came from a home with may other Nortons, wondering now if the oil tank came off another machine?
 
The Picture looks similar to the tank in my Mk3, I guess the choices you have is either a reducer or can you remove the oil tank and modify to the correct pipe size.
 
Thank you! I'm assuming a reducer could be found in a plumbing parts store, maybe barbed 1/2 to 3/8. We may have another tank hidden in the boxes, I'll check that first.
 
possm said:
I guess the choices you have is either a reducer or can you remove the oil tank and modify to the correct pipe size
Click to expand...
SO HE IS NOT ALLOWED TO FIND A TRADE?
The
rear external pipes is slighty different length too.
The reducer works for little money ...
 
I know not the same year ('74), but that tank looks identical to mine, and it has a steel reducer nipple just in front of the tank's nipple. Look in your spare parts grab bag for a silver/grey cad-plated piece of tubing about 1 inch long. Or, go pick up one of these: 3/8 X 1/2 Barb
 
I had the same as maylar. I believe that was the stock set up but no idea why.
 
I've since made a trip to NAPA auto parts, ended up with a length of 1/2" hose and a corresponding reducer. Glad to see others were done this way. Its now installed and I'm still a long way from starting this up. Just finished rebuilding both master cylinders, can't wait to see where the fluid comes out first!! Next electrical, one of my weaker points. This is a lot different than my first MC which was a 200CC Triumph Tiger Cub! Thanks for all your help!
 
I use a breather valve from a car in the tube which vents fumes from the crankcase. If there is none there, the air in the pipe does not flow, it stands stationary while the motor is running. You need to have the situation where the breather sucks, even it does not at high revs. The internal diameter of the tube is probably irrelevant. Mine is only 3/8ths of an inch and it works well to stop oil leaks.
 
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