Oil not returning after couple months sitting

Hi All

I was doing some repairs to the transmission, primary drive, alternator and rotor so the bike sat idle for the last couple months as i slowly got to each issue I found. Once i completed the repairs and was ready to fire it up and go for a ride i emptied the sump of oil and made sure there was the proper amount in the tank. Started it as normal and looked in the tank to make sure oil was returning like I always do....and there wasn't any...for a while. So i pulled the left hand side rocker feed banjo and started the bike and that was squirting plenty of oil. I took off the return line at the engine and blew air up the hose into the tank and there was no obstructions. So i started the bike with the return line off the engine and nothing was coming out....I even covered the pipe with my finger to feel for pressure or air pulses and felt nothing. So i have feed up to the rockers but no return at the pipe behind the engine.

Whats next and how should I go about it?

Thank you all.

Is there any oil in the sump now, when you drained the sump the return side of the pump would have nothing to suck on for a minute or so, maybe it's now air locked and needs priming or the pickup from the sump that then goes to the return pump is now blocked. Or you just need to run the engine longer until some oil gets to the sump.

Check the screen in the sump plug.

Do you have an external oil filter, and did you put in a new filter just before this happened?

A new oil filter will take 1 to 2 minutes to fill before oil returns to the tank.

There is no pressure to be felt in the return oil line if there is no oil flow, so do not be concerned that you felt nothing. Of course, you need be concerned why there is no oil flow.

Slick

texasSlick said:

Check the screen in the sump plug.

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I think it's a '73 750, so no sump strainer plug.

When I started mine after years of sitting, it took several minutes for the oil to be visible in the return. I was getting worried, and then it appeared. If in doubt, just remove the plugs and kick it to prime.
Jaydee

Update

L.A.B. is correct, it is a '73 750. Sorry, I realized I forgot to mention that when i saw Slick's post asking about the sump plug screen.

It does have a oil filter but i have not changed it in 600+ miles. I didn't change anything involving the engine or oil system since it was last working for a couple hundred miles.

I have started it a few times since i first started this topic just to show/explain to my dad what i was having issues with. After the few minutes with it running i emptied the sump and there was at least a cup of oil, if not more, that drained from the sump. So there was various amounts of oil in the sump during the last several times i'v started it.

(Warning: Non-union/non-mechanic practices about to be explained) After explaining some of this stuff to my dad he wanted to check some stuff out his own way...he's not a mechanic or a Norton guy but maybe it can give you guys some more info. So we hooked up some clear tubing to the return pipe on the engine and tried to blow and suck through the tubing. Nothing budged. We couldn't get air to pass in or out of the engine through the return pipe (we even tried when it was running too). I know nothing about the oil pump but i thought that we should atleast be able to blow some air into or out of the engine through the pump. Even with it running we couldn't the pressure or vacuum to change or pulse the slightest bit. However, before i drained the sump this last time i started it and the motor lifted oil in the pipe up to the end of the pipe but no further...when i turned it off the oil drained back down. All of this is hard for me to explain, so, i'm sorry if this is confusing or doesn't make any sense...just thought it might help pinpoint the problem.

theocean said:

Update

I have started it a few times since i first started this topic just to show/explain to my dad what i was having issues with. After the few minutes with it running i emptied the sump and there was at least a cup of oil, if not more, that drained from the sump. So there was various amounts of oil in the sump during the last several times i'v started it.

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If you have emptied that cup of oil out of the sump, there won't be anything to pump back into the tank !!,
for a while anyway. And it might take a while for the pump to prime and start pumping returning oil.

Take it for a ride around the block (assuming its only a few hundred yards), and then look and see if oil is getting back to the tank.

I had kind of a similar issue with my '73 model (with no big sump plug, just the drain plug).
The issue with this model is where the oil in the crankcase is picked up to go through the oil pump and return to the tank. There is an important modification to change the pick up point to the rear near the breather tower.

My problem did not return oil to the tank through the return line, but the crankcase filled with oil and only returned through the breather line right at the top of the oil tank at the cap due to crankcase pressure. Turned out that the oil pump return was blocked by a wad of silicon sealant that got loose inside.

Suggestion: with the engine running take off the oil tank cap and use a flashlight to visually check the oil return point.
If the oil level is too high you might not see it returning.

Also since you didn't mention about the oil supply line, remove the supply line (engine off) at the engine pipe and verify that you have gravity flow into the engine.

Good luck with it.

theocean said:

Update

L.A.B. is correct, it is a '73 750. Sorry, I realized I forgot to mention that when i saw Slick's post asking about the sump plug screen.

I have started it a few times since i first started this topic just to show/explain to my dad what i was having issues with. After the few minutes with it running i emptied the sump and there was at least a cup of oil, if not more, that drained from the sump. So there was various amounts of oil in the sump during the last several times i'v started it.

(Warning: Non-union/non-mechanic practices about to be explained) After explaining some of this stuff to my dad he wanted to check some stuff out his own way...he's not a mechanic or a Norton guy but maybe it can give you guys some more info. So we hooked up some clear tubing to the return pipe on the engine and tried to blow and suck through the tubing. Nothing budged. We couldn't get air to pass in or out of the engine through the return pipe (we even tried when it was running too). I know nothing about the oil pump but i thought that we should atleast be able to blow some air into or out of the engine through the pump. Even with it running we couldn't the pressure or vacuum to change or pulse the slightest bit. However, before i drained the sump this last time i started it and the motor lifted oil in the pipe up to the end of the pipe but no further...when i turned it off the oil drained back down. All of this is hard for me to explain, so, i'm sorry if this is confusing or doesn't make any sense...just thought it might help pinpoint the problem.

Click to expand...

These symptoms suggest a blockage in the return port from sump to scavenge side of pump. Read again Bob Z's post.

Pulling the timing cover may be in order, then the oil pump to inspect the scavenge port. Try to see if there is any obstruction in the scavenge port. Do not simply poke a rod thru the scavenge port as this might push whatever is obstructing the port into the sump, only to appear again later. Perhaps Bob Z can elaborate on how he cleared the blockage in his case.

Also, check that the oil pump drive worm is firmly fixed to the pump shaft. The fact you have oil pressure at the banjo, indicates this is not the problem, but it is worth an inspection.

Keep giving updates.

Slick

I found and cleared the silicon blob by removing the timing cover and oil pump. There it was, the blue stuff right where the oil pump paper gasket is.
The blockage did not allow scavenging back through the pump and back into the tank.
I also removed the drilling plug at the lower front right of the engine cases. This is where the machining of the oil pickup and path inside the crankcase casting is. I ran a pipe cleaner though the line to hopefully get anything else that could get sucked up from the bottom of the cases into the pump.
This worked for me to get oil scavenged properly and back into the tank.
The real fix is of course to split the cases and re-do the oil pick up to the rear. There are many posts on how to do it.

Looking back, what was Norton doing by eliminating the big sump plug and screen, and oil pick up, on this series of engines?

I hope this helps. If you are careful you can remove and replace the timing cover without replacing a good camshaft oil seal. But it's a great time to inspect the oil pump outlet cone seal and timing cover oil seal.

I have been thing more on this case. The OP's stated fact that oil rises to a certain level, then immediately falls on shut down of the engine makes me think there is a bypass route for oil direct to the timing case. I cannot reason how oil can flow back to the engine so quickly thru the gears, and with the possibility of an obstruction in the scavenge port.

What if a small piece of metal (what and from where?) got between the gears on the scavenge side of the pump. Such a condition could very well split the pump housing and allow oil to flow directly into the timing case. Just trying to cover all the bases. The OP should inspect the pump carefully.

Slick

Curious what happened here?
Also, are lines correctly placed? I recall there is a discrepency between the picture in manual and what is correct. Somewhere there is a proper (e.g. correct) diagram.

arbrnrngr said:

Curious what happened here?
Also, are lines correctly placed? I recall there is a discrepency between the picture in manual and what is correct. Somewhere there is a proper (e.g. correct) diagram.

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Curious and frustrating as well, when OP's do not feedback.

Slick