Airbox drain pipe!

der

Joined
Sep 23, 2013
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68
Does everyone check the drain pipe from the air box to make sure it isn't fouled up with chain oil or road crud? If like me you don't then you'd best start or else you'll end up with a day like mine :(

After getting my bike back from service at Norton last August I was pleased to find that the emulsified liquid that dripped from the drain pipe had stopped, today I found out why....... the bloody pipe was blocked solid causing the air box to fill up with emulsified liquid, which when braking hard descending a hill caused the liquid to exit the airbox down into the injectors . masses of smoke ensued and an engine cut out!
 
air filter after removing from air box.
Airbox drain pipe!


looking in to the air box, the crud is now 1cm deep after dripping for over 3 hours (after clearing blockage in pipe)
Airbox drain pipe!


after clearing up with paper towels!
Airbox drain pipe!


stopped on the way home to make sure I wasn't doing some damage and 2 hours after releasing the blockage it's still dripping away (3 drips per second)!!
Airbox drain pipe!


BP the mileage is 4,600 miles
 
I was advised by my dealer about the air filter issue.
The mist from the engine breater saturates the paper air filter element.
It has a real impact on performance.

Was not aware of the drain hose clogging problem.

Thanks for the info.
 
Mine drips, especially if I overfill the oil, but never that fast. I'll keep a closer eye on it, thanks.
 
Hi there
1200 miles on my sport 961, Sorry to rub it in but great weather all year round in Aussie.
After first service i drained about 50ml of oil from air box.
I keep the oil on dipstick between low mark and bottom of dipstick. I have a small plug in the hose which I can remove to drain oil .
Get into the habit of draining it after every ride 100 miles or so. if you don't drain it it will build up and saturate filter. and worse go down intake .
Norton's still leak oil Its just controllable now !
Love the bike getting better every mile.
cheers
Paul
 
Use a larger diameter ID Hose . This should prevent blockage. The hose looks tiny , too small ?
 
Also looks like some galvanic corrosion around the ground bolt near the air box mouth. Maybe clean reconnect and grease it ?
 
TonyA said:
Also looks like some galvanic corrosion around the ground bolt near the air box mouth. Maybe clean reconnect and grease it ?

it looks corroded in the picture but it isn't in reality. Norton rebuilt my bike in a new frame seven months ago, it's done 900 miles since and looks as good as it did then.

The pipe may be too thin but it's the same as fitted to all the 961's. I don't think it's the emulsified stuff that's clogging it up though. A thick black goo came out the bottom half inch of the pipe, more likely the pipe had been routed under the engine and pointed in the direction of the chain and chain oil had hit the pipe then clogged it.... dunno just thinking. Prior to Norton changing the frame my drain pipe was a little shorter and hung loose pointing down to the road and never became clogged in 3,700 miles.
 
On this topic, also good practice when you receive a new bike to make sure the ZIP TIES are not too tight from the factory. My dads bike had the zip tie so tight on this hose it blocked the drain.

SIDE NOTE: Position the drain away from the BRAKE side of the wheel. Because if you overflow the oil, it drains out that hose and when driving goes on your rear brakes.. which means little to no rear braking. My dad also experienced this issue of no back brakes because he didn't fully understand that you had to check the oil level within minutes of shutting down the engine. All good once you know how but at first this one gets a lot of people. Even professional mechanics like him.
 
I too overfilled the oil level several times before speaking with my dealer. I waited too long after shut down and always discovered a low oil level. So I refilled the oil to a point midway between the low and high marks. I had oil exiting the overflow hose on to the exhaust pipe. Made a mess. The hose was routed to the rear brake side as well.

Found out that the correct level has to be measured within 1 to 2 minutes after shutdown, and the correct level is the low mark of the dipstick. Not between the low and high marks. Every refill that I did was an overfill. Wish the engine was designed with a wetsump/view window like the Hinckley Bonneville.
 
BritTwit said:
Wish the engine was designed with a wetsump/view window like the Hinckley Bonneville.

Once you are used to it, it's not an issue. This is why NORTON CANADA made a really nice detailed YOUTUBE video of changing oil.
 
The oil change vid from Norton Canada is a good one. Can some one repost the filter number. If I remember correctly, its the same cartridge filter used in some Mercedes Benz, which of course will make them very available to us. Especially since the dealership doesn't seem to keep many in stock.
 
Has anyone purchased an air filter yet ? That may be a good idea to have a second one handy . I should ask about the price . Thanks.
 
Also , Can the air filter in the above image be washed , allowed to completely dry and reused . Said so in the Norton manual.
 
TonyA said:
Also , Can the air filter in the above image be washed , allowed to completely dry and reused . Said so in the Norton manual.

My dealer said the air filter is paper, and has to be replaced if it gets oiled by the breather.
Which appears to be the norm when overfilling the oil.
 
Is this emulsified liquid due to me overfilling the oil?
The drain pipe on my bike dripped from day one of ownership, meaning Norton over filled the bike after building it. Likewise after it's 1st 2nd and 3rd service from them it dripped the emulsion. I was told it's a big air cooled twin thing more than an oil overfill.
 
The oil vapor is pumped due to pressure changes in the crankcase due to blowby from the rings, and from volume changes as the pistons move up and down in the bores. As the rings seal after run in the blowby is minimized, but the changes in crankcase volume are always an issue. Our 961's have 270 degree cranks, so the pistons do not always rise together and fall together as they do in a 360 degree twin, like a old 750 or 850 Norton. So our 961's should not be pushing a great deal of oil vapor or emulsion into the air box unless the oil is accidentally overfilled.
I had a constant drip from the airbox on my 961 until I finally realized I was overfilling the oil. Once I learned the correct method of measuring the oil level my overfilling stopped, and so did the anoying airbox drip. I still touch the end of the hose periodically, and it is moist and leaves a film on my finger, but no drip beneath the bike.

Just a word about the big twin problem, my Hinckely Bonneville is a 360 degree twin so the pistons do pump air pressure in the crankcase as they both fall together. I thrash the bike constantly, the breather rarely deposits any oil in the bottom of it's airbox. This is because the crankcase breather is properly designed for a modern big twin.
 
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