Please clarify re oil in the combustion chamber

[Carson]

Yes, me again...I have read all the posts re getting oil in the combustion chamber and I have done numerous checks suggested, such as yes I have new guides, no the rings are not upside down etc.
What I am vague about is that oil blow off valve that houses the filter just below the dynamo? It is not clear (at least to me) if that valve is malfunctioning would that result in oil getting into the combustion chamber? If so what is the fix? Or is there another oil valve that I am confused about?
If I sound desperate it is because I am, never in all my years of dealing with engines have I been so confounded by a problem!!


Thanks, in advance, for your help....Carson

[Carson]

Lol...well that question worked out well??

[robcurrie]

The most probable cause of oil in the combustion chamber is poorly sealing piston rings. You should also read up about "wet sumping", because that also contributes to the problem.

Rob C

[Carson]

Thanks for those suggestions Rob, much appreciated, but the rings are in the right way up and have had about 100 miles of break in on them and as for wet sumping I have an anti-wet sumping valve that I turn off as soon as the bike is parked. So I feel reasonably confindent neither of those issues are the problem.

[clive]

Lol...well that question worked out well??

Diagnosis by Internet is not always easy and your first thread got lots of answers.

The pressure relief valve you mention by the Dynamo is unlikely to be the cause. It role is to reduce the oil pressure when you first start the bike and the oil is cold. It works by bleeding oil into the timing side cover and a malfunction would result in reduced oil pressure, with no chance of extra getting into the combustion chamber. Once the oil is warmed up it does not operate.

There is however a second pressure relief valve mounted in the nut that holds the driving gear to the shaft on the primary side. This is intended to relieve crankcase pressure as the pistons come down and is a one way valve, breathing out into the primary chaincase. Now if that was malfunctioning the crankcase pressure would build up as the pistons come down and allow/force oil up into the combustion chamber. A check, if a little messy, would be to run the engine with the primary cover off and look/listen for evidence of the valve working. Take care with your fingers, I nearly lost the top of my thumb whilst fiddling with a running single without the primary cover on. If this valve is malfunctioning the club spares scheme stocks the nut.

Ps you will shortly find as a guest member that you are no longer able to start a new thread as your three months is up.

[SPRIDDLER]

the rings are in the right way up and have had about 100 miles of break in on them

I know little about AMC twins and pressure relief valves, but in principle oil can only enter the combustion chamber via the valve guides or past the piston from the c/case (unless you are using 2-stroke mix).
Did you fit new rings because oil was previously getting into the combustion chamber?

IMHO 100 miles is not enough to break in new rings whether or not th'engine has been bored.
If you only fitted new rings did you deglaze the old bores? I'm assuming that all your checks included that the ring gaps were correctly spaced and are correct?

EDIT.....(Just noticed that you have started a new and second thread on the same issue so my comments are probably superfluous).

[Carson]

Thanks guys for those very informative replies, I will now give more time for break in to see if the problem lessens and then move on to checking the oil valve. Good concrete ideas that I can explore.

[Carson]

Clive, one last question before I open this NON-leaking primary chain case to examine the oil valve....is this the same valve that if it malfunctions causes the chain case to fill with oil, as I do NOT have that problem.

Carson

[clive]

I do not think a malfunction on the valve in the primary chaincase would result in the chaincase filling with oil. You are probably muddling the problem with that of wet sumping, oil draining through the oil pump into yhe crankcase when the vehicle is left standing, in the case of my twin much worse when left on the side stand. This could of course also be the reason for your smoking engine. Once the crankcase has filled to the level of the bearing it drains into primary chaincase. But well before it gets that bad it will cause very bad smoking when the bike is started. So if your smoking problem is when the bike has stood for a while, and you have not ridden the bike a number of miles, then this could be the cause of the smoking. Try draining the sump plug and see if this sorts out the problem. If you try this check the oil level because If it has wet stumped and you drain the sump there may not be enough left in the tank.
Basically the valve in the primary chaincase allows the crankcase to breath out into the chaincase when the Pistons are going down. If it failed open it would simply breath in and out as the Pistons moved, the problem I am suggesting is that it could have failed closed. This would prevent crankcase pressure being relieved and would tend to blow the oily air past the rings.

[Carson]

10-4, I do not have a wet sumping problem so tomorrow I will take off the primary cover and check out that valve. Curious thing is that my 54 Parts book does not seem to have any parts or pieces relative to that pressure relief valve?

Carson