Mayonnaise, anyone?

[veloduke]

The crankcase breather just above the kickstart on my Mototrans 250 broke, so I fixed a long tube ending by the rear mudguard as some later bikes have.
The tube is beginning to fill with that creamy oil/water mix, and showed moisture in the tube ever since I fitted it.
The original breather had a one way valve in it, and I wonder if moisture has got into the engine owing to the absence of that valve?
When I ride the bike I tend to do 50+ miles, so it's getting hot OK.

Any thoughts as to what else might be happening?

I'll probably source an original style breather and fit that.

[Bevel bob]

Some oils seem to be better than others at keeping the oil and water seperate. The Duc single runs very cool and never really warms up on winter runs in temperate climates. 50 miles will not do it on my 250. !00 miles on the Norton gives me plenty of mayonaise ,thinking of Insulating the oil tank, or adding a 12v imersion heater.

[Duccout]

I think it is just normal for a cold, wet climate; hot air and oil mist condenses in the pipe. Now if your engine was water cooled......

[blethermaskite]

Max I think you are sorta right about the one way valve, most Ducati singles I have owned or worked on have had the long breather pipe to the back of the bike (on race bikes this has to terminate in a ventilated catch bottle/tank), on road bikes this breather always displays internal condensation even when ridden hard, on race bikes a lot less or none at all, I think its simply a matter of how hot the engine gets and the volume of hot air blowing out of the pipe....however on the late widecase (italian) singles I have owned with the relatively short breather pipe and the one way flap valve I would say there appears to be less condensation in the pipe (the standard Italian widecase breather pipe is black plastic so you can't see whats going on in it) I use clear pipe on my bikes and can see whats happening. As already mentioned Ducati singles generally as a road engine run quite cool and are a big lump of metal to get warm enough to evaporate any condensation inside, for this reason I never start my bikes without the intention of a long hard run to get them properly "cooking" and thus hopefully dispose of the water. So I think the one way flap valve tucked away inside the air box stops to a degree the interface between the warm air being blown out of engine and the cold air of the atmosphere .......or maybe I'm just blowing humid bubbles?
Cheers,
George

[veloduke]

Sounds like I need a valve.
My 125 has the mushrom type breather that was on the 250, and I've not noticed any salad dressing in that engine. Mind you, you have to go everywhere on full throttle, so it gets a bit hotter!!

[themoudie]

Max, I have never had any mayo' problems with the '74 450 MKIII, I have always used a clear plastic tube from the crankcase either into the air box where the air filter should be, or just left open under the seat. The only "problems" have been an oily mist deposit over everything that get's heavier as the bore wears! A quick wipe with cotton waste soon sorts that out and it waterproofs the electrics.

On the other hand a '79 Morini 125H and a '86 Morini 350 K2, both with the same breather arrangements into the air filter box and similar to that used by the Ducati, apart from plastic baffles inserted in the tube, directly above the crankcase. These always have a build up of mayo' around the base of the tube and baffles that requires cleaning out at the winter service. The baffles are deemed "necessary" by the manufacturers and the Morini Riders Club forum, as the back pressure that they create in the crankcase ensures that there is an oil mist lubrication for the rockers, there being no positive lubrication system for the rockers in the modular engine design.

The 450 MKIII runs on Morris 40W oil, whilst the Morinis run on 20/50W multigrade, so there might be something in this? But, I believe that an overly long tube, or an obstruction in the tube encourages the condensation of oil and water vapour in the tube the further away from the heat of the crankcases you move and this then runs back down to the tube base and into the crankcase.

I would advise keeping the tube short into a rear mudguard or bottle catch tank, with 30cm - 40cm to the open end from the crankcase vent and without any obstruction to the open end of the pipe. Many race bikes have these sorts of arrangements as it is easier to arrange, rather than long trailing tubes.

Good health, Bill

[veloduke]

Thanks Bill
It's interesting to hear other's experience. If I sort it out, I'll post again here.
All the best