[Thomas]

It's always the same, you can't come up with the simple ideas yourself... the blow/suck test says that the breather is fine. I think I leave everything as it is but regularly observe it.
Thank's again, Rick.

[Rick Parkington]

OK I see, well at least you should be able to get a rubber pipe onto the metal pipe shown in your picture and try the blow/suck test, then you'll know whether or not you need to take off the magneto, let's hope not!
Cheers Rick

[Thomas]

Hi Rick, the oil flow is not very big. My 1946 BSA C11 is a mess compared to it. That's why I had to dismantle and test the breather of this machine. So, at least for the BSA I am familiar with crankcase breather.

It seems that the breather pipe does not goes to the rocker box but directly to the crankcase (as it does for my BSA). The pipe-crankcase connection is almost invisible and very difficult to reach under the magneto platform. The connector looks like the oil feed pipe to the rocker box, as shown in the pictures. The background of my machine is known to the club. It comes from the late Kenneth Rawlings in Swindon, went to Ywan Schuchewytsch in Brussels who drove the bike for only 300 miles within 6 years and went to me last year. So, I have some reasons to assume that Kenneth Rawlings brought it into ist great shape.

I have wet sumping only in spring after it was in my shed over winter. No real trouble here. I guess it is a good advise just to wait how it goes.

Best, Thomas

[Rick Parkington]

Hi Again Thomas, as Vic says crankcase pressure is a possible - not sure how your model breathes, you said before your bike is 1937, I think? I know the '37 250 has a disc-type breather on the rocker box cover so I guess yours is the same. Breathers can stick open or closed and cause a problem, if you blow and suck through the pipe you should feel it working, it need not be a perfect seal but it must open and close. Older engines were often designed to run with a slight vacuum to assist with oil sealing, that's why the breather needs to close, stuck open it just keeps sucking back what it breathes out.
Not sure what the background of your bike is but if you bought it as it is, it may just not be very well sealed. Leak prevention depends on care of assembly, choice of sealant and engine health. The usual cause of crankcase pressure is combustion gas blowing past worn piston/rings/bore, wet sumping of course can also increase pressure although this is usually an easily spotted problem.
But older bikes all tend to leak oil so it may just be the way it is. If it were me I would just see how it goes. If it doesn't upset you too much and doesn't make too much mess you could ignore it, keep topping up the oil and leave it   until the time comes to pull the engine apart for other reasons.
The leak is unlikley to be from the head joint - there's not supposed to be much oil in there! - if that is the source, the oil will be burned, sticky and black and not likely to drip anywhere. I'm not sure if series 2 models use a head gasket or are just lapped together with valve grinding paste to seal metal to metal like the earlier Sunbeams but I think your leaks are more likely to be from the rocker box than the head joint. Base gasket is possible, but it still could be oil from the rocker box leaking down the outside of the pushrod tubes and running round.
Cheers Rick   

[Thomas]

Hi Vic, it's a 1937 Model 9 (see my signature). You mean my crankcase breather could be blocked? That is what I also considered. For testing it I need to dismantle the magneto, right? On the other hand I do not expect an issue here. The machine is in very good condition and everything is actually fine. But who knows...
Cheers, Thomas   

[VicYouel]

Remind me what model  and year your bike is Thomas; if 1932 onwards have you checked the breather? it may be due to excess crankcase pressure.

Vic

[Thomas]

Hi all,

after a 100 miles run I had some oil mist on the oil tank. After one night there have been again
some slight leaks indicated by drops at the bottom frame and the bottom of the crankcase. It seems that the oil comes from the cylinder foot but maybe also from the head and I wonder if the head bolts have to be tightened. What is your experience with such a situation. Should I accept the issue as it is? Should I do something against it?

Cheers. Thomas