Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Oil Sumping / Air cleaner sucking - hack?

Last several start up's, the Three Wheeler had sat a bit and a slurp of oil got sucked into the air cleaner.

I would like to avoid this. I am assuming the oil is sucked up through the breather hose from the sump. If prior to starting I simply disconnected this breather line, or if I even added a shut off valve in the hose, I am assuming this would prevent this behavior? I don't see any issue doing this? Am I missing something, or is this a quick way to stop this and avoid having to drain the sump prior to starting after an extended sit with no negative effects?

Since the S&S ECU won't allow the engine to fire up when cranking with the throttle open you could try cranking the engine over for a few seconds with it fully open. This should mean next to no vacuum trying to draw oil up from the crankcase while the oil is scavenged from the sump.
That's the theory...I didn't think to try it till after I had changed to a different ECU that would probably instantly have it bouncing off the rev limiter.
You don't really want to block any of the crank case breather hoses as a rise in pressure might blow out the crankshaft oil seals if you forget to unblock them.

I think the possibilities of screwing things up is increased by disconnecting hoses or, as others have suggested, isolation valves to prevent the oil draining into the sump over time. I know it is possible but....... Maybe just draining the oil from the sump after a prolonged period of inactivity is the safe option? That is unless you strip the threads on the sump plug but that is another story.

There certainly would be risk if the vent line was blocked off. What about this approach. A valve that in position A allows normal crankcase vent pass through to the air cleaner. Position B allows venting the crankcase to outside air. Worst case is if you forget to put back into normal operating position, the crankcase is vented but not under vacuum. Is negative crankcase pressure a requirement?

DO NOT block the vent line. You can simply vent the crankcase to atmosphere (with some sort of filter on the end).
A better idea is to consider an air/oil separator. Check out my post here: http://www.talkmorgan.com/ubbthreads.php/topics/647169/breathing-without-slobbering#Post647169

Thanks for the link.

So why is the vent line going to the carb? Is the reason strictly to reduce emissions? Is there any other reason to vent to the intake?

The reason it's going to the carb is Positive Crankcase Ventilation (PCV). Besides the emissions, PCV is very helpful in minimizing oil leaks as it creates a slight negative pressure in the crankcase. If you are going to vent straight to atmosphere, I would recommend a larger opening and pipe from the crankcase. There is at least one unused port near where the vent/drain from the oil tank comes into the cam box.

Google "benefits of positive crankcase ventilation" or something similar and you'll find plenty of reading.

It also occurs to me, there is a related issue here. IF you are running with your oil tank vent/drain in the lower position (which was typical from the factory) it will not fully drain oil mist after use due to having a low spot in the tubing run. AND if you make a few short trips that don't fully boil off accumulated moisture in the crankcase especially in these cooler days of autumn, you can end up with a foamy sludge blocking that vent line until thing warm up. SO with the vent line plugged, on startup, the engine cannot vent excess pressure to the tank and it has to go somewhere, so the intake vent tube seems like a good place, blurping oil into the intake.

Search on this forum (or Google it, as the search here isn't great-Google results for M3W searches typically bring up this forum!) for posts on M3W breather or crankcase breather and you'll find posts on the simple drain line modification to help these issues.

Just fit an oil catch tank - works well for me.

And beware about undoing the sump plug - as planenut states - there's not much in the way of thread in the crankcase so its easy to strip the thread......

Good advice and a nice trick with an MMC S&S ECU to crank the engine to push excess oil out of the sump. I shall try it soon.

Another warning with the sump plug, if you do remove the plug make sure it is fully home and tight when refitting if not the vibration will cause it to come out. I discovered this with catastrophic results requiring a new engine.