Engine oil system - how quickly to pressurise?

[MB-Ian]

When I talk to people about warming up the bike, or ask on here about the choke and warming up the bike (see me other thread) people often comment that it takes minutes for oil to make its way to all the critical parts in the engine and start lubricating. A few minutes seems like an extremely long amount of time for parts to be "dry" before the oiling starts.

By way of comparison I work on Mercedes V8 engines which have a oil pressure guage and you can observe through the oil filler the cam-oiler tubes so basically you can see how long from when the engine starts, until the oil system is pressurised, the cam oilers being the last part of the oil path - furthest from the pump. On the MB engine from the engine firing to the oil pressure needle moving takes around 1 second and the oil to start appearing from the cam oiler is about the same amount of time, which is about 6 cam rotations (12 crankshaft rotations).

How quickly does an XS engine pump its oil around the engine? Japanese manufacturers being pretty cluey, I don't think they'd design an engine which ran for minutes before oil makes it to the cams etc...

Anyone got any thoughts on this one?

I.

 

[gggGary]

Yeah you are a lot closer with your 1 second than others are with minutes. The oil in the pressurized system does not drain out when you shut down the engine so it repressurizes quickly. The big end (and other) bearings in the XS are roller bearings so oil at start up is not an issue for them. The cylinder to piston gap holds oil also. While you don't want to do burnouts or full throttle acceleration when the engine is cold, most modern advice is once you can get the engine to run while off full choke, gentle riding is the best way to warm things up. The worst enemy of engines is too thick of oil and cold starts. With a close second or even worse being leaky carbs. If the oil in the passages is too thick the pump cannot move it along to lube things. Multiweight is better than straight weight no matter what your grandfather says. Not many of us ride our motorcycles much below 0C so no worries.

 

[XSLeo]

If you want to time how long it takes , remove one valve adjuster cover, start the bike. It won't take but a few seconds to get oil spraying out.
Some oil gets there quick. It takes a bit to replace what drains out with a full charge of oil.
If you come back from a ride and imediatly check the oil after shut down, then check again after 15 minutes or so, you will see the oil level rise. This rise is from oil draining back out of the engine. This is the oil that takes awhile to replace. If you let the bike set for a week then measure how long it takes to spray out the valve cover you will see it takes longer. Still not minutes but longer than when done when the bike is ridden everyday.
I hope this helps you understand what was meant.

 

[Hutzpah]

MB-Ian

My 1979 xs650 makes a single click from the head which has bothered me I would think
its one of the tappets.
I have had the bike sitting for a couple of days then started it up and used the stopwatch on my phone to take the time it takes to stop.

Which has been no more that 14 seconds.

What I do is start the bike then put my helmet on do up the jacket.
Then ride it a short distance out of the shed, lock up the shed then jump back on the bike.

This gives it abit of time to warm up and get some oil pumped around.
I hope that helps.

Hutzpah