Oil tank return flow

Should the return flow be clearly visible on a ‘71 with a full oil tank? The flow is not easy to see or judge with a full oil tank at idle.

Return flow must cerainly be visible, although because the return part of the oil pump has a larger capacity than the feed , the return oil flow will be mixed with air bubbles.

The flow is not easy to see or judge with a full oil tank at idle.

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yes it should be easy to see as the flow is on top of the tank level with motor running, unless you have put in more than the specified 3 quarts

If there's something wrong with the scavenge, the crankcase will fill up with oil. Is that happening?

You should be able to see it flowing looking through the filler hole but if you have over filled your oil tank you won't see it, 1/2 tank full be the lowest level and 3/4 of a tank will be full so don't fill any higher or your tank be over filled.

Ashley

In lieu of a direct observation of flow, the first clue will be the oil level in the tank remaining steady or coming up a bit.........unless your feed side oil pump is totally on the fritz.

The oil level is at the low to medium side of the dipstick. It is not coming out the crankcase overfill return line. I will look harder to see if there is any swirl in the tank, indicating a good return.

Will check it again this weekend and might remove the timing cover to check if the oil pump nipple has a good seal to the cover.

At idle it's a fast dribble but when you rev it up a little you will see it shoot out sideways from the tube.

I'm wondering what you mean by 'crankcase overfill return line' – there's only one line that returns oil from the engine to the oil tank, no? Although I've no experience of a '71 ... I'm only aware that the shape of the tank had changed by the time they made my '74, but if the plumbing essentially stayed the same, the oil return line vents just inside the tank from the filler neck, not below the surface of the oil (unless it's over-filled, as already mentioned), so you can see the oil pouring/spurting/bubbling from the top of the line, like this – if that style of plumbing applies to your tank, and you're looking for swirl in the oil, you're looking too far down into the tank! And, again unless the tank's over-filled, that'd suggest that you're not seeing any oil issuing from the return line. That'd be serious. You don't have a shut-off in the oil supply line that needs opening, do you? Sorry, I had to ask! Otherwise, you need to check that oil's getting to the pump and that the pump is working. HTH, and that I'm not telling you stuff you already know ...

BTW, in that video, in case you don't know, the tube entering the neck of the filler, that has some white goo in it, is the end of the breather hose. The white goo is one reason people like to fit one-way valves or catch bottles in their breather hoses, to keep that stuff out of their engines.

batrider said:

At idle it's a fast dribble but when you rev it up a little you will see it shoot out sideways from the tube.

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This is what I see on mine.

Before the startup were you working under the timing cover ? Perhaps the oil pump gasket got reversed.

Torontonian said:

Before the startup were you working under the timing cover ? Perhaps the oil pump gasket got reversed.

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Nope, never. Bike had been cosmetically restored and I bought as a non-runner.

If it is getting oil to the nylon black head feed line and there is no oil coming out the breather, the pump and timing cover seal must be good. I probably just have a low return pressure at idle. I’ll rev it up and see if i can see it coming out more.

If you have troubles seeing it maybe stick your finger under the filler hole to where the return pipe is you will feel it I am sure get oil spaying on your finger but if you shine a tourch in the filler hole you should be able to see it when reved it should be flowing constantly.

Ashley

The flow is there. The bright So. California sun was just preventing me from seeing it adequately. Thanks all.