Sumpin's Wrong

Due to circumstances I had to let the Commando rego lapse a year ago but am now in a position to re-register the old gal. I'd booked a roadworthy inspection for this morning and rode the 30ks down the highway to get this done. Bad news is the inspection didn't get far when it was noticed that there was a rather large amount of oil on the nice inspector man's floor. Rode back home and spent the arvo trying to find where the leak was. (Not a pleasant task as it hit 43C in my garage!) Checked all pipes and fittings and tappet covers. Cleaned the engine with degreaser and took it for another ride. Oil seems to be dribbling from virtually every gasket face. What's going on? Crankcase is pressurising I'm guessing. I've put an XS reed valve on the breather down the back of the engine and vented this into the oil tank (across-frame tank not pannier / side-cover style) and this should make the bike more oil tight, not less. Any clues?

It sounds like crank case pressure to me too.

Are you sure the reed valve is working? Is it in the wrong way around? etc.

Make sure the oil tank is vented and the cap is secured properly.

Dave - So it's been sitting for a while? Remove the XS breather and check that it is not gummed up with 'mayonnaise'. They tend to do this. Blow through it - the reed valve should vent freely in one direction and not the other. What's the compression pressure like when you kick it over from cold and warm? Is it burning oil on acceleration? What are the plugs like? Black and oily or burning clean? If it is burning oil and you are getting those oil leaks, it might be a broken ring (hopefully not), or gummed up rings.

You didn't by any chance overfill it with oil after it had been standing?

Sure sounds like a deficiency case of a-cute sporty k/n filter-itis, aka: ring edge and gap wear blow by beyond capacity of reed valve control aggravated by anti-drain valve dry sump start on dry bores with a bit of rust scoring from forgetting to leave jugs near TDC. Guess what Norton used so effectively in the days before anti-drain valves and and one way breather valves, Hylomar from Rolls Royce aircraft.

Drained sump and got about a half litre out last night - sound like a wet sump or is that about right? Will pull the reed valve apart and check for gunk. Managed to get the RWC this morning, only a single drop of oil on the floor after the 30k ride in. Will investigate more after work tonight.
Thanks for the advice chaps.

Dave,

it is also possible that you have an obstruction somewhere from the crankcase breather tube up to the oil tank itself, and then from the oil tank there is the other hose going to the atmosphere, or to your air filter?

I would remove each of the lines and blow compressed air through the various hoses

sure seems like something is blocking your breathing and causing pressure to build in the crank......

Nothing wrong with the reed valve and all clear through the lines to the tank. Got my club rego yesterday so ride #1 was a quick highway fang down to Kilcunda.



Just got there as it was getting dark - hence the crappy grainy 'phone pic. Also wasn't keen to shut it off, so notice the rather high idle. Seems to have crept up since I left home - will have to look into that.
No oil leaks by the time I got back, so must have just been a full sump. Thought any excess would be pumped out in the first couple of seconds of running though???

davamb said:

Nothing wrong with the reed valve and all clear through the lines to the tank. Got my club rego yesterday so ride #1 was a quick highway fang down to Kilcunda.

Just got there as it was getting dark - hence the crappy grainy 'phone pic. Also wasn't keen to shut it off, so notice the rather high idle. Seems to have crept up since I left home - will have to look into that.
No oil leaks by the time I got back, so must have just been a full sump. Thought any excess would be pumped out in the first couple of seconds of running though???

Click to expand...

Takes more than a few seconds... watch the return rate through the oil fill hole...