Wet sumping head ?

Hello all,
I have a problem with a mk 11a 850 commando that blows out a lot of blue smoke after a run.
When started from cold there`s no smoke.
Ive done a compression test- both sides at 160psi- Ive done compressed air into the plugs , no leaks from valves.
Its only noticeable after 10 mins plus of riding and then only at a standstill. Reving the motor from tickover produces loads of blue smoke.
I`m reluctant to take the head off as everything else checks out ok.

At the weekend i went for a ride and when i returned i immediately took the inlet valve cover off, there i noticed a pool of oil. Now i dont know if this is normal but i measured the depth and it was a good 15mm deep. It took 10 minutes for the oil to drain away to 3mm. I took the measurement from between the inlet valves as close to the carburetter side as possible.
See pic.


Now the stupid question, is there a blocked drain hole? and if there is , where is it in the head as i could`nt see any holes.
I hope this is the answer to my problem as I`m stumped otherwise.

Many thanks for any info.

The drain hole on the intake side is next to the bottom of the right hand valve spring. It is partially obscured by the spring cup.

Thanks for that, is it possible to get an airline to it?

Oil drain clog popped to my mine too. Drain is in rear RH corner of rocker. Here's top of barrel looking front to back to see the smallest hole at 10'o'clock position that lines up with hole in bottom of head. Gasket and/or goop can block it. It goes through cases to drool out raw into TS case. Not sure even if wire poked down head would help as likely not blocked in head passage. ugh.

Could it be that the rocker spindles are fitted wrong? The flats should face away from the oil feed holes.

It certainly sounds like the drainback hole is restricted. It usually happens when someone gets carried away with the sealant either at the head gasket or the base gasket. You can get to the hole by removing the timing cover and you might try clearing it with a shot of air. Jim

Yes it may be gasket sealer, or slightly out of line gasket.
Do you really want to blow it down into the motor.?
Could this be a case of Crankcase compression.?
AC.

AussieCombat said:

Do you really want to blow it down into the motor.?

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My thoughts exactly. Think about it, did it clog from something coming up from the bottom going against the drainage - it's feasible but not likely.

Have you had this motor apart (top end) where you used a gasket sealant; this may give a hint as to what you might be up against. If the answer is no then it is more likely you have some sort of loose unidentified blob or debris blocking/plugging the drain back hole from above.

If the motor has not been apart recently then I would see about coming up with some sort of way to aspirate with a small metal tube that can fit between the valve spring and the lower right hand side of the valve chest adjacent to the RH intake valve. Just don't blow yourself up doing it (in other words I would not use a shop vac for this) as the oils and vapors are combustible. I think the spring cup partially covers the drain hole but there's clearance provided by the insulating washer beneath the spring cup. You should be able to just see it when the oil clears. You could maybe rig up a make shift venturi to a jar and use that as an aspirator. Might also get a dental pick or a cotton swab to see what you can dislodge if the blockage is at the valve.

If I recall correctly, the rear head drain empties into the timing chest (somebody please correct me here). If this is the case and other attempts at clearing the drain fail, pulling the timing cover may give you access to the drain hole in which you could apply compressed air. If that fails, then maybe some probing with wire. If that fails, then off with the head. If that fails, then off with the barrel.

Here's some pics of the drains:

Intake:





Exhaust (one each side that drain into push rod tunnel):



As Jim says you can blow air though the timing chest drain to force blockage back up to the head. Where the oilway joins this exit port from the passage in the barrel there is a right angle bend so wire won't work. If a gasket is flipped backwards it will block the oilway as well although a lot of gaskets have holes on both sides to prevent this accident.

Thanks for all the replies guys. I will try to get it sorted at the weekend.
Just for info the engine was totally rebuilt 2 years- 4000 miles ago by Norvil, who know what there doing. I would`nt think they would overdo the sealant or get a part the wrong way round.
As long as this build up of oil is the problem ,I`m happy.
Its the not knowing that bothers me.

Chris r

Hope for a blocked drain.
The alternative which is all to common with the rh4 head is a cracked guide hole and/or a loose guide. Jim

Thats cheered me up no end, Jim.
Maybe the big man up there will take pity.

chris r

blacklav said:

Thats cheered me up no end, Jim.

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Hate to tell you, Jim's an optimist

Duh, dude, we are all optimists when it comes to these mysterious fault ridden Commandos, similar to entering and enduring a marriage for better or worse, if ya love em enough.

Take outside or over a covering and start up and look to see if oil shows up in higher amounts than can drain out, as 4K miles on skilled build engine don't bode well optimistic blocked passage.

Let's hope he can clear it out by blowing through the timing hole and the culprit will blow out.

Dave
69S

Blacklav
You don't say if the smoke is coming from one or both pipes.
If from both I'll agree that the oil drain being partially plugged sounds logical.
Since it doesn't happen immediately if it is the drain it sounds like a partial not full blockage since after sitting for a while it must be draining.
However if the smoke is from one pipe then I'd start looking at a valve stem seal having split.

Bob

Kind of off topic, but didn't Kenny Dreer run a drain line from between the valves to the Mag plate on the VR880's? Any point to it?

Blaclav, is there a quality crankcase breather fitted.
Could the problem be Crankcase pressure.
Oil won't drain away if there is too much pressure against it.
A friend had the same problem (oil biuld up in the head) with his Atlas race motor, a breather fixed the problem.
Just a thought.
AC.

rpatton said:

Kind of off topic, but didn't Kenny Dreer run a drain line from between the valves to the Mag plate on the VR880's? Any point to it?

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Kenny used a separate oil drainback tube because the ports were widened to the point of getting into the original drainback hole which then had to be plugged. Jim

Ugh! Hobut , I`m feeling depressed now.
Even if this 13mm of oil is a definate fault ( indicating the blocked drain) how can it get into the engine if the inlet valve seals are OK?
I think the quick answer will be to take the head off and be done with it
Ho hum.
chris r