Mayonnaise

Maestro, SEI-V
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Mayonnaise

Post by penman »

Yesterday I decided to re-check the valve clearances on the 500, having done about 400 miles since re-commissioning. I was quite shocked to see a LOT of "mayonnaise" in the front cylinder rocker box. Looking further, the breather pipe was full of it, as was the breather collector box and the two pipes to the air cleaners. Removing the various pipes to blow them out, there was a lot of water in there. I haven't seen mayonnaise for years, it's something I associate with clapped out Ford Anglias and the like and I don't remember seeing it in air cooled engines before - and I've never seen it in this quantity.

Correct me someone if I'm wrong, but I believe the mayonnaise is actually an emulsion formed by oil in water - typically condensation under the rocker cover mixing with oil mist(?) On those old pushrod car engines, I think it was mainly associated with worn bores and a bit of blow-by. Short journeys probably didn't help if the engine rarely got fully warm.

The engine is running well and so far, I've never ridden it less than about 40 miles at a time, so I am confident that it is always reaching normal operating temperature, and staying there for a good while. Searching this forum, I found mention that a loose dipstick can cause this, though I think that is by allowing water ingress. The dipstick wasn't loose, but I've replaced the O-rings anyway. There is no mayonnaise in the rear cylinder rocker box. I have also had a look on my 350K2, which has the same breather system, but there isn't a hint of mayonnaise anywhere.

Someone has borrowed my compression gauge, but I'll have it back today and check the compressions. They feel OK and even as "judged by foot" though and the bike starts easily and idles well.

Any suggestions anyone? I've cleaned it all out so I'll see if it returns.

Many thanks!

Joe.
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
Papa Lazarou
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Joined: 10 Nov 2016 09:42
Location: Sussex

Re: Mayonnaise

Post by Papa Lazarou »

Mayonnaise is, as you say, an emulsion of oil and water.

It's much more common in water cooled engines (think leaking head gasket). I'm no Morini expert but finding mayonnaise in an air cooled engine means one of two things to me:

1) there's water getting into the engine-it's leaking in somehow. For that, you'd need to have somewhere the water gets in plus a supply of water-driving through heavy rain, pressure washer cleaning. If the bike is kept under cover and only ridden in the dry, this seems pretty unlikely.

2) an engine which hasn't seen much use can have condensation on the inside. Running it, cleaning out the resulting emulsion and changing the oil usually sorts it.
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Re: Mayonnaise

Post by penman »

Papa L - thank you, a useful bit of logical thinking. I haven't used a pressure washer on this bike and it hasn't yet seen the rain. That's luck, no doubt it will sooner or later! The bike had been standing for around 20 years and certainly there was plenty of moisture in all sorts of places. However, I cleaned out the sump as best I can with paraffin (air/paraffin gun through the oil strainer hole) to remove considerable sludge and I would have though that would drive out any water, unless there is a hiding place for it which I haven't spotted. The breather box was clean and dry and all the breather tubes are new. I started (of course!) with new oil and I changed it at about 130 miles. Maybe I'll change it again.

The front cylinder is running slightly richer (or cooler) than the rear judging by the plug colour, but I would regard both as being well in the "normal" range. As I mentioned, I'll get the compression gauge back from my mate today and I'll check that just to be sure.

A small spot of mayonnaise wouldn't bother me, it's the sheer quantity that's bothering me. The breather box was literally full of it.
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
Papa Lazarou
Posts: 156
Joined: 10 Nov 2016 09:42
Location: Sussex

Re: Mayonnaise

Post by Papa Lazarou »

I had a friend who had an old Vauxhall which was full of emulsion. It worked great until I decided to clean it up for him and change the oil....

No, just run it. Emulsion always comes to the top. Then change the oil.
Steve Brown
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Joined: 12 Nov 2007 23:44
Location: Leicestershire

Re: Mayonnaise

Post by Steve Brown »

I'd agree with Papa above, get it really warm (as you have been doing) then change the oil again, and possibly again till it flushes out. My 350 only ever gets this if I do short runs in the cold damp weather so I try to avoid that. As a further thought, I have found some engines don't seem to like some oils! My 750 Matchless for instance always makes mayonnaise and condensation in the bottom of the oil tank if I use 20W/50. If I use monograde oil it doesn't do it! Not worked out why, just carried on with monograde.
I'm hoping to sell that 750 so if anyone is interested..... 8) I'll be advertising it soon.
All donations to the rest home for old Camels, Leicestershire.
Papa Lazarou
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Location: Sussex

Re: Mayonnaise

Post by Papa Lazarou »

A 750 Matchless? CSR?
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72degrees
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Re: Mayonnaise

Post by 72degrees »

For the front pot to be the only culprit suggests a possible ring problem on that cylinder to me.
MickeyMoto
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Re: Mayonnaise

Post by MickeyMoto »

I have seen this. A good thrash is helpful. Took the rocker cover off and I could not believe 'mayonnaise'. Was going to sell it to Helmanns!

Just checked my car, got some in the oil filler cap. 'er indoors does 3 mile journeys, so see above for this weekend's activity.
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Re: Mayonnaise

Post by penman »

Thanks for the replies folks!

I checked the compression today and I got 205psi on both cylinders - I don't think that gauge has ever been up so high! I couldn't do a leakdown test because I couldn't find my adapter, but with compression readings like that, I am pretty happy that nothing scary is going on.

I thoroughly cleaned out the breather collector box and all the tubing, as well as both rocker covers. I didn't have time to do a proper test ride but I did ride it up and down the road several times and I noticed that the rear rocker cover gets significantly hotter than the front one - not really surprisingly. So, if mayonnaise is going to form, I guess it is more likely in the front rocker box where there is a cooler surface to condense onto. That's my theory anyway. With the piston movement, I guess there is significant air movement in the rocker breathers as well as in the crankcase breather - maybe that also leads to condensation in those tubes.

I still don't know where the moisture is coming from, but for a short while I am prepared to assume that it'll dry out with use. If the mayonnaise reappears in quantity though, I'll have to re-think. Still open to other ideas and suggestions!

Joe.
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Re: Mayonnaise

Post by penman »

MickeyMoto wrote:I have seen this. A good thrash is helpful. Took the rocker cover off and I could not believe 'mayonnaise'. Was going to sell it to Helmanns!

Just checked my car, got some in the oil filler cap. 'er indoors does 3 mile journeys, so see above for this weekend's activity.
Thank you! I like the "good thrash" idea, it sounds a deal more interesting than grovelling around on the floor with bits of rag, mopping up that white muck!
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
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72degrees
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Location: West Midlands

Re: Mayonnaise

Post by 72degrees »

penman wrote:
MickeyMoto wrote:I have seen this. A good thrash is helpful. Took the rocker cover off and I could not believe 'mayonnaise'. Was going to sell it to Helmanns!

Just checked my car, got some in the oil filler cap. 'er indoors does 3 mile journeys, so see above for this weekend's activity.
Thank you! I like the "good thrash" idea, it sounds a deal more interesting than grovelling around on the floor with bits of rag, mopping up that white muck!
"Dealer's decoke". Hopefully that will sort it. Not a phenomenon I have ever noticed - at least not on just the front cylinder. When I had broken rings on mine years ago it was on both pots and it was still easy to start and went surprisingly well. Just copious emissions from the breathers, which as it happened during mid summer didn't have time to form splooge, but left an impressive vapour trail and led to a very oily rear number plate.
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Ming
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Location: Central France

Re: Mayonnaise

Post by Ming »

[quote=
...Thank you! I like the "good thrash" idea, it sounds a deal more interesting than grovelling around on the floor with bits of rag, mopping up that white muck![/quote]

..."Dealer's decoke". Hopefully that will sort it.[/quote]

I was always told it was an 'Italian tune-up', apt really. One of my basic tools too...
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Re: Mayonnaise

Post by penman »

I am highly indebted to Ming for the term "Italian Tune-up", which I shall use with pleasure from now on!

So, as instructed, I did the Italian tune-up in the form of an 83 mile blast and I enjoyed it greatly. There are definitely no cobwebs on the "East side" of the rev counter face now. However, the mayonnaise is back, once again in quantity. The two tubes from the breather collector box to the air cleaners are transparent and are absolutely full of white emulsion. The two tubes from the rocker covers are black, but pulling them off, they appear to be full at both ends. There is also a little visible in the big crankcase breather, also transparent, but it's not clear which direction it has been coming from, it may have entered the breather from the collector box or from the crankcase.

I must say I am mystified by this, it seems to indicate quite a lot of water inside the engine, but where has it come from? It has done about 170 miles since the last oil change, so I guess I must clean out all the emulsion and change the oil again. To clean it out thoroughly is a couple of hours work because the collector box really has to come off the bike and that involves removing the tank, battery, rear rocker cover and of course all the pipes - a fiddly and tedious old business! I've had another look at the 350K2 and there really isn't a trace of emulsion anywhere, and that was filled with the same oil from the same can at the same time. So I can't blame the oil.

Any suggestions? Otherwise I'll proceed with an oil change and clean-out once again.

Joe.
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
'It must be a .....'
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Joined: 12 Sep 2010 12:25

Re: Mayonnaise

Post by 'It must be a .....' »

Hi, it all sounds rather odd. I've only seen this when commuting (8 miles) in the winter and it wasn't too bad.
On UK 500s there are no air box breather pipes; the air box holes are blocked with plastic bungs and pipes go to atmosphere from the collector box and I wonder if this set up would help?
So from the collector box the bottom large pipe connects with the rear of the engine and 2 of the four small top pipes go to the rocker boxes and the other 2 to atmosphere; quite quick to do and worth a try.
Hope this helps.
penman
Posts: 325
Joined: 08 Mar 2016 09:20
Location: Milton Keynes, UK
Location: Milton Keynes

Re: Mayonnaise

Post by penman »

'It must be a .....' wrote:Hi, it all sounds rather odd. I've only seen this when commuting (8 miles) in the winter and it wasn't too bad.
On UK 500s there are no air box breather pipes; the air box holes are blocked with plastic bungs and pipes go to atmosphere from the collector box and I wonder if this set up would help?
So from the collector box the bottom large pipe connects with the rear of the engine and 2 of the four small top pipes go to the rocker boxes and the other 2 to atmosphere; quite quick to do and worth a try.
Hope this helps.
Interesting. This is (was) an Italian bike, imported a year or so ago. The breather collector box had been completely bypassed - a short open pipe on the crankcase breather, no pipes on the rocker box breathers and sticky tape sealing the two short angled pipes in the top of the air cleaners. Someone must have done that for a reason. I have restored it to original (the same as on my K2) and this is the result!

On the UK bikes, where were the two breathers from the collector box routed to? - forwards, backwards, short pipes, long pipes?? I'm guessing that if I did this, emulsion would be pouring out of those pipes. I'll give it some thought, perhaps I'll try routing those pipes into a plastic bottle to see what comes out. I still don't know where the water is coming from!
1984 Moto Guzzi V65
1969 Honda CB450
1975 Triumph T160 Trident
2019 BMW F750GS Sport
1978 Morini 500
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