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Re: A slight case of wet sumping -Do I need to worry?

OK,

Only Ron understood my question not other people who have answered, I obviously was not clear enough when describing the problem. I'll have another go:

1. The bike ONLY wet sumps when running at idle for 10 minutes

2. The bike does NOT wet sump while parked.

3. The bike did not smoke when I started it, it came after 10 minutes of idleing.

4. The problem is not in anyway related to the piston rings.

5. It is the oilpump that is not returning as much oil as it is filling the engine with, AT IDLE.

6. The problem goes away when revving the engine.

7. I interpret this as a sign of the oil pump beginning to lose its oumph.


MY QUESTION: Do you agree with me regarding number 7 and does anyone have a similar experience with an oil pump?

My next question is of course what can I do to fix it? Apart from buying a new pump. I'm thinking perhaps milling some parts of the oil pump housing down in order to make the gears a tighter fit? Was such a long time since I put it together I only have vague memories of how it looked... :wink:


Best regards,

Simon

Re: A slight case of wet sumping -Do I need to worry?

Hello Simon,

I don't know if this will help, but it's based on my experiences with 1930s bikes.

I am assuming you ran the bike at idle while on its rear stand.

If so, then it may be possible for the oil to 'pool' in a pocket somewhere in the bottom of the crankcase - the engine is not perfectly level when the bike is on its stand, and this can happen. If so, you will get excess oil that the oil scavenger pump cannot reach, and it will cause the engine to smoke. I puzzled over this with a Matchless that would do the same thing when idling on its side stand, and it nearly drove me to sell it on. Once I put the bike level I had no such troubles.

I'd suggest trying the ten minute idle with the bike held level on its tires, and see if that makes a difference. It won't cost you anything, and it might help.

Best wishes, and Good Luck!

Allan

email (option): allanmatchless@yahoo.com

Re: A slight case of wet sumping -Do I need to worry?

Thank you Allen, that is very useful information!

The bike was in fact not quite leveled, it was on a side stand and also slightly uphill.

I will look into this further before doing anything else such as removing the oil pump for service.

It does seem odd to me that the “pump ratio” on the in vs the out side of the pump changes with revs.

Best regards,

Simon

Re: A slight case of wet sumping -Do I need to worry?

['It does seem odd to me that the “pump ratio” on the in vs the out side of the pump changes with revs...']..

I'm not quite sure what you mean there Simon...The feed gears have a smaller pumping capacity relative to the return gears as the system is a 'dry sump' system...This ensures the crankcase is scavenged (dry) when the engine is running and is the reason on initial start up that a constant flow will soon turn into an intermittent one once any residual oil is cleared from the crank case....

The capacity of both sides of the pump increases or decreases in proportion to rising and/or falling engine revs but not independently of each other...Ian

email (option): ian@wright52.plus.com

Re: A slight case of wet sumping -Do I need to worry?

Ian Wright
['It does seem odd to me that the “pump ratio” on the in vs the out side of the pump changes with revs...']..

I'm not quite sure what you mean there Simon...The feed gears have a smaller pumping capacity relative to the return gears as the system is a 'dry sump' system...This ensures the crankcase is scavenged (dry) when the engine is running and is the reason on initial start up that a constant flow will soon turn into an intermittent one once any residual oil is cleared from the crank case....

The capacity of both sides of the pump increases or decreases in proportion to rising and/or falling engine revs but not independently of each other...Ian
"The feed gears have a smaller pumping capacity relative to the return gears as the system is a 'dry sump' system...This ensures the crankcase is scavenged (dry) when the engine is running and is the reason on initial start up that a constant flow will soon turn into an intermittent one once any residual oil is cleared from the crank case."

Yes, thats exactly what I meant Ian. Why would it wet sump at idle-revs and then dry sump at higher revs?
It did but it makes no sense!

Best regards,

Simon

Re: A slight case of wet sumping -Do I need to worry?

I think Allans theory is the best fit for that...Ian

email (option): ian@wright52.plus.com

Re: A slight case of wet sumping -Do I need to worry?

If you think the scavenge pump is the problem.

Idle the bike until it starts smoking out the exhaust. Shut the engine off and remove the drain plug and see how much oil actually comes out.

Do the same test with increased RPM's until it does not smoke and drain it again. The oil quantities should be identical.

Re: A slight case of wet sumping -Do I need to worry?

Hello Simon,

Did you ever resolve the problem?

Best wishes,

Allan

email (option): allanmatchless@yahoo.com

Re: A slight case of wet sumping -Do I need to worry?

this happened to me on a unit Triumph. had me stumped. after a rebore, new pistons and rings, new valves and guides it still kept wet sumping while I was riding. Eventually I pulled the oil pump and found a tiny piece of hard crap that was caught in the scavange side ball bearing. A five minute fix which took me several months and quite a lot of money.

email (option): cas.vanderwoude@gmail.com

Re: A slight case of wet sumping -Do I need to worry?

Allan Hunter
Hello Simon,

Did you ever resolve the problem?

Best wishes,

Allan
Aloha,

And thanks for asking, been busy doing other things so have not gotten round to look into it.

/s

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