Hitchcocks Forum

I have a 1951 350cc bullet which I have just completed with a new barrel etc. It is running, but I have a regular drip of oil coming out of the breather pipe under the primary chaincase.
I do have oil circulating and returning to the oil chamber.
What does this indicate and how can I solve the problem?
Many thanks
Dave

I think you'll find they all do that sir! And that's why the breather moved to the higher location on the barrel from the following year. You could try extending the pipe with a bit of rubber tube so that it feeds over the top of the gearbox sprocket, that may help.

REgards, Mark

Do you think it could be blowby which may resolve when you've put a few hundred miles on it and bedded in the rings.

Sometimes they go a bit overboard with the cross hatch honing and it makes for a poor ring seal for the first few hours.

Maybe completely wrong of course.

It is quite a lot to just divert to the drive sprocket. I,m getting a sizeable pool just running it on the stand, also, it comes out when I'm kicking it over.
There certainly seems to be a pressure building up to push the oil out.
The crankshaft nut itself hasn't anything inside it, should there be a valve or something to restrict what comes out? I have a cork seal on the end of it which fits into the recess in the chaincase cover.
What are your thoughts?

Over filled it with oil?

That is a possibility, I don't like to think I have too little oil in an engine so I will check.

"should there be a valve or something to restrict what comes out?"
Not sure if the old bikes had a duckbill on the end like the more modern ones but it's certainly worth a try. The idea is that the breather can breath out but not back in again. This helps to maintain a lower pressure in the crankcase.
It may also be worth leading the breather pipe "up and over" behind the battery so that oil can't escape so easily.
Have you checked that the scavenge pump is working properly? If it's leaving excess oil in the crankcase it is likely to be ejected through the breather.

Is it wet-sumping? My Indian Bullet chucks loads out if it's not run for while.

Thanks for your comments, been away for a few days and contemplating my options. Not sure that routing the pipe high would be a good idea as the tube would fill up with oil, increasing the crankcase pressure it's mean to lower. I am considering a high capacity scavange side pump but not sure it's suitable for a 1951 bullet, can I fit it without a high capacity supply pump? I have oil returning into the tank as a light steady flow, is that correct or should it be pumping out?
I need to speak to our hosts to clarify things, also check that the oil level isn't too high in the crankcase and tank.

"Not sure that routing the pipe high would be a good idea as the tube would fill up with oil"
I don't think it will - it will drain back as fast as it rises.
You could try clear tube then you could see what's going on.
Oil should be returning to the tank as you described but look at the flow to the rockers. The flow there should be intermittent as the scavenge pump should be pumping more than the feed.
High cap. pumps are a waste of money on a normally tuned engine IMHO