1936 vb 600 oil build up in timing cover

[oliverjp]

Hi i have a 1936 Ariel vb600 after starting despite good scavenge back to the tank i get excessive amounts of oil in the outer timing cover .it eventually leaks out of the lower breather and magdyno shaft seal . i have good oil pressure and i have replaced the balls and springs in the pump after many years of Ariel ownership i am stumped with this as i don't have this issue with my other singles . Any ideas as to the cause would be welcome ?

[volker.halbach]

Sounds familiar. Pre-38 timing cases have the oil drain holes much higher than later engines. This is my 37 inner timing cover:

There are also correspondingly higher drain holes in the crankcase. Do you have the higher drain holes? Later covers have just one drain hole much lower.

It makes a big difference how far the lower breather elbow is screwed in. If it's flush with the inner cover, a lot of oil will leak out; more surprisingly, if it's too close close to the chain, it will also leak more oil.

Do you use a later oil pump with the bigger delivery piston? If I fit a later oil pump, I leave a trail of oil drops. I have switched from SAE50 to SAE40 oil, which seems to help with the oil in the timing case. Having said that, more oil leaks past the piston rings. On my 100mls journey to the Ariel rally, I used about half a litre of oil at 35 Celsius and traffic jams in Gloucester! Normally it's much less.

I asked people with pre-38 bikes whose bikes don't leave a puddle of oil behind. Usually they had blanked off their lower breather in the chain case.

[nevhunter]

There's more cylinder Distortion with side valve Motors and therefore More BLOWBY when they are worked hard . 3 Compression rings helps. Those breather elbows are not that well designed. The VEE remains in some cases and that's designed to provide more oil (For the rear chain or the front one in an early Model)?? By many standards the Breather is not large enough for the Blowby volume in anything bur a fairly new Bore and rings.Nev

[oliverjp]

Sounds familiar. Pre-38 timing cases have the oil drain holes much higher than later engines. This is my 37 inner timing cover:
IMG_20260331_135512.jpg
There are also correspondingly higher drain holes in the crankcase. Do you have the higher drain holes? Later covers have just one drain hole much lower.

It makes a big difference how far the lower breather elbow is screwed in. If it's flush with the inner cover, a lot of oil will leak out; more surprisingly, if it's too close close to the chain, it will also leak more oil.

Do you use a later oil pump with the bigger delivery piston? If I fit a later oil pump, I leave a trail of oil drops. I have switched from SAE50 to SAE40 oil, which seems to help with the oil in the timing case. Having said that, more oil leaks past the piston rings. On my 100mls journey to the Ariel rally, I used about half a litre of oil at 35 Celsius and traffic jams in Gloucester! Normally it's much less.

I asked people with pre-38 bikes whose bikes don't leave a puddle of oil behind. Usually they had blanked off their lower breather in the chain case.

My timing cover is identical to your cover . but for some reason oil gathers inside to the point where it is leaking out of the magneto drive .i have blanked the lower breather off as oil was pumping out of it .The only thing i have not checked is that the sludge trap is not full and is some how restricting oil flow to the big end causing it to back up in the timing cover .

[volker.halbach]

With these timing cases there is always a lot of oil in the chain case. I also believe that oil can escape around the quill, especially when the oil is thick. When I pump oil by hand into the crank, there is a lot of resistance because the oil ways are really small. Excess oil then leaks out at the quill into the can case and from there into the outer case. It's better with thinner oil. The biggest difference made when I switched from the later oil pump to the older. I would check this first.

[oliverjp]

Hi there ,that is a very good point about the heavy viscosity of oil causing the oil retention in the timing cover i will try a lighter grade and see if it helps

[nevhunter]

Light(thin) oils were never recommended for those Motors. The critical areas for wear are the Camshaft lobes and followers. Check if oil is getting to the big end and consider making the Quill seal better..
It may be off centre or worn when the Ball race had some play or Mainshaft run out.. Don't rule out Blowby. It DOES produce similar results.

[nevhunter]

A super effective oil ring can reduce the sealing of the Compression rings as well as significantly increase engine friction. Different ex Valves may require different EX Valve Tappet settings. Side valves get hotter than OHV valves do due to the crook shape of the Combustion Chamber. A BLUE Pipe is more common also and they require More ignition advance. Nev

[volker.halbach]

I read somewhere that the old oil thickeners were broken down much quicker than the modern ones, so that SAE 50 turned quickly into something thinner. The 1938 owner's guide for Germany actually recommends 30 for the winter to facilitate starting.

My quill is definitely somewhat off centre, but with no rumble from the engine or wobble at the end of the crank. But even when everything is perfect, new quills have a relatively loose fit, and oil will escape there.

[oliverjp]

I have removed the sump filter and removed the oil sludge trap in the flywheel and there was no sludge or material that would restrict oil flow to the big end . The quill looks unworn so i will reassemble and try using 30 grade instead of the current 40 and see if that helps with the timing cover drainage . To be honest i cant see any real issues ,there is minimal blow by on the cylinder and good compression . thank you for your assistance