Won't return to idle/slight oil seep...

[Mikep328]

Thanks Ian. I'll take a look under that cover this weekend and see what's happening.  Hope no major disassembly work will be required to sort out whatever it is.  If such work is required, I'd probably just let it seep for a while and enjoy riding the bike!

Julie, appreciate the talc suggestion; I'll definitely do that!

[McCabe-Thiele (Ted)]

The slight oil seep I have does not appear to be from the pan gasket. It is dripping from the cover on the left side of the engine adjacent to the pan and then down the side of the pan.  So based on an earlier post, the suspect is the gear change seal?

I suppose I could use the oil seep to determine if there is oil in the bike as per old BrittBikes - "If it's not leaking it's out of oil!"  But I'd prefer the typical Honda method - no oil leaks at all!

Sounds crazy but I found new oil especially 10w/40 synthetics would leak oil via the rear main seal on cars - after a few days or a 100 miles they would disappear - I put it down to the thin searching  oil & plasticizers that they add to modern oils then fixing the cause.

[Mikep328]

Good advice re checking instead of ASSuming the oil pan gasket was the leak.  I removed the left side cover and found that the leak is at the lower left (as you face it) of the oil pump.  It seeps immediately upon starting the engine.  no leaks from the oil pressure sender. I'll check the service manual for the procedure to remove/replace the oil pump seal but if anyone has some specific advice re this, don't hesitate to post!

This added several minutes later:  It appears from the service manual that the pump has essentially three Orings - a large one and two smaller ones that appear to fit around the lower bolts AND that the pump can be removed without draining the oil.  Is my reading correct?

[McCabe-Thiele (Ted)]

There are 5 O rings in total in the oil pump.

[Nurse Julie]

There are 5 O rings in total on the oil pump.

There are 8 in total on the 400 Ted, including the gearbox oil pump O rings.

[McCabe-Thiele (Ted)]

Oops it's not a 500 its a 400 they have those extra rings - my Bad - either way more than 3 by quite a few.

TBH I had forgotten just how different the two oil pumps are.

[Oddjob]

Try and lean the bike to the right when removing the oil pump in order for any oil to drain back into the sump. That's if you're not dropping the oil that is.

[Mikep328]

Good idea, will do!

[McCabe-Thiele (Ted)]

Just a thought if your oil pump is leaking oil - could the cause be linked to something else that has caused the leak?
I'm thinking oil pressure valve, oll filter valve?

[Oddjob]

Probably just the age of the orings Ted, if they are original they are really old now.

[Mikep328]

According to receipts the engine cases were separated to do various work, including a DSS cam chain tensioner "upgrade" so I ASSUME the oil pump was reinstalled with new O rings.  Maybe an Oring wasn't seated properly or moved out-of place during assembly?  In any case, I hope the cause will be obvious and easily resolved with new Orings. 

[Oddjob]

Doesn't mean they've removed the oil pump though Mike, if it's not needing to do the work they'd have left it in place

[taysidedragon]

I took one engine apart and the oil pump o-rings were in a hell of a state, had not been replaced, just smeared with orange silicon gasket. Not everybody puts it back together properly. 😣

[Mikep328]

That's interesting -  Never having done it (or looked up the procedure), I had assumed that the pump had to be removed to split the cases. 

Actually, I hope the pump was NOT removed previously.  If it was and is leaking due to some faulty assembly, it will make me wonder about the quality of the considerable engine work that was done...£2,216.85 worth per the receipt!;) 

This added a few minutes later:  After leaning the bike to the right for a bit then placing it on the center stand, when the pump is loosened/removed will any oil - other than residual oil in the pump itself - be draining out?  Will I need a catch pan or will a few rags handle it?

[Nurse Julie]

Always best to have a tray and some rags handy Mike. Ideally you need to keep the bike leaning to the right through the process.