Oil flow to head

I have a unusual oil coolers mounted to the front frame down tubes…1 for each cylinder…3/4” ID tube x 12””with cooling fins…Will the oil in those lines and coolers drain back into the sump past the oil pressure relief valve ?
Thanks,
Rod

If oil comes out of the back of the timing cover goes through the coolers then into the head on both sides to feed the rockers, the oil will drain over the cam and back into the sump like it usually does from the head. However, I have no idea how your setup is plumbed. The coolers look cool. Edit: where is the pressure relief valve on your bike? If it was my old bike it would appear to have been removed in the first pic.

I'm probably missing a technical step in my comment. Somebody will spank me shortly.

Hi. Short answer is yes. Your oil pressure relief valve regulates oil pressure to the top end feed lines entering the oil coolers at the bottom. I guess the oil lines at the top are connected to the cylinder head. As Schwany wrote, from inside the cylinder head, oil drains back into the crankcase sump with no restriction apart from flow restrictions imposed by rockers and rocker spindles.

Your plumbing is unusual, IMO. Oil coolers are usually hooked up between oil return line and oil tank. Oil temperature in the oil return line is much hotter than oil temperature in the top end feed line, and the flow is also much higher.

- Knut

I was just trying to cool the oil before it enters the head…I measured 7-8* cooler @55 mph..95* ambient temperature…kinda disappointed on the amount of cooling. My question is… does the oil in the cooler return to the sump when engine is stopped thru the oil relief valve?

The relief valve is just above the double banjo in first photo…not shown

How is it actually plumbed, is there a loop at the bottom ?

Out of timing case with stacked banjo into separate lines to the bottom of each cooler. The output of each cooler goes to separate inputs to head…hope that makes sense

Britbike850 said:

I was just trying to cool the oil before it enters the head…I measured 7-8* cooler @55 mph..95* ambient temperature…kinda disappointed on the amount of cooling. My question is… does the oil in the cooler return to the sump when engine is stopped thru the oil relief valve?

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The oil pressure relief valve opens when the pressure is high. With the engine not running, the pressure is low so oil does not bypass the oil pressure relief valve. Oil in the lines to the head will, over time, leak back to the sump via the oil pump unless you have a check valve (not standard in pre-MK3; MK3 has one standard).

IMHO, lowering the temp a little in the rocker feed not going to reduce the head temp enough to notice. Makes more sense to cool the return to the oil tank as @mdt-son said. That oil has been in the crank, sump, and head.

Britbike850 said:

My question is… does the oil in the cooler return to the sump when engine is stopped thru the oil relief valve?

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The oil in the coolers would drain back to the timing cover gallery where it would drain to the sump through the crankshaft (if not positioned close to TDC) unless there's some leakage through the oil pressure relief valve or threads.
Your Commando appears to be a Mk3 which is the only Commando model that would do this (unless fitted with a Mk3 timing cover) as previous Commandos sent the oil from the relief valve back to the inlet side of the pump.

Thanks for all the replies…It is a MKIII…there was more oil in sump than I expected…new oil pump had solved the wet sump issue that I was having…oil coolers have added oil to the sump while sitting for long periods…guess I need to break down and buy a sump reed valve breather …
Thanks again for the replies,
Rod