No Oil Pressure After Rebuild

The oil pump needs primed. After the rebuild it is dry with no oil in it. It needs oil to help it seal so that it will create enough vacuum to draw the oil out of the sump.
My 907ie did this last spring after I had drained the oil in November but didn't fill it with fresh oil until the spring. The oil in the pump had drained out into the sump. The solution was simple. I removed the oil pressure switch and used an oil can to squirt oil down the hole until it was full then refitted the oil pressure switch. When I then started the engine the oil pressure light went out instantly.

 

I'm assuming you have sufficient oil in ? Oil capacity is 4 litres'ish ? Not wanting to state the obvious... I had tried spinning my engine over after an oil change and, not wanting to overfill, with the resultant hassle of trying to remove excess, had not quite out enough in. Result was oil light wouldn't extinguish. Topped up and all was fine.

 

Like Derek says, it needs a while to build pressure up after a rebuild, especially if you've swapped out the cooler etc. The whole system needs to be primed under load.

Geoff Baines advised me that those engines have got a pretty shallow sump so you might want to run it a little on the brimmed side anyway. I used to run mine so that the sight glass was nearly full.

 

I ran my 750SS with the oil level about 2.5mm below the top of the sight glass.

It didn't lose or use oil at all (or none that you would notice, anyway).

 

Does the three litres take account of the oil in the filter??

 

The oil capacity is quoted as 3.5 litres which is what it will need with a completely dry rebuilt engine. On oil changes I usually find that they take around 3.1-3.2 litres to fill to the upper line with the residual remaining in the engine.

 

I dont suspect this is the problem if the oil pump wasnt removed at all, but would a missing oil pump O ring cause this? Just curious

 

At the risk of throwing in a red herring here's my experience on my 748.

I had an issue after I'd recommissioned it last year (and done an oil change as part of that) with the low pressure oil warning light coming on. It had happened once before in the bike's past shortly after it's first service, but the dealer supposedly fixed it. I know I used the correct amount of oil to fill it back up again so I knew it wasn't low oil. Having read on here about pricing the pump I did just that, as explained above, but to no avail.

Unsure of why I should have low oil pressure when I had an engine that had only done 2600 miles at that time , isn't leaking oil anywhere, or burning it, I bought an oil pressure gauge and took the measurement - 5 bar, within the range it should be. When I went to replace the oil pressure switch I thought this is weird, 'why is there no washer between the switch and the crankcase cover? its just the metal switch butting up against the metal seat on the cover. There definitely wasn't a washer there when I took it off just a few moments ago'. On checking the parts diagram sure enough there should be a washer there, so I found a washer of the correct diameter, fitted it and re-fitted the switch. I've never had the same problem since.

It seems that by lifting the switch out by the thickness of the washer it can better read the pressure of the oil underneath. I've no idea why it worked, but it did.

Are you perhaps missing that washer?

 

Theres two, sit between pump and case. As shown here....

 

Whenever I rebuild engines, I never use straight engine oil; but usually coat all moving parts with a 25% oil to 75% mix of Wynns Oil Treatment....the treacle-y stuff, like STP.

It does mean that when firing up for the first time, there is enough lubrication while the proper engine oil starts to get around.

 

Homemade assembly lube!

 

And why not, eh?

Sticky as hell.......not so bad in a mix, but neat Wynns makes a mess.

I made a mistake when I rebuild a Guzzi Le Mans engine and used it neat........would it start? Eventually, but it shagged the battery charge and I had to use jump leads from the car.

Exhaust smoked for about 5 minutes.

 

Why not indeed, I think its a great Idea as I just bought some Lucas assembly lube which was expensive for the amount I got.

 

Have you tried a pressure gauge in the pressure switch hole?

 

I don't know the bike at all but when rebuilding an engine as @Arquebus has stated. Everything gets coated in an assembly lube.

Next as also stated some pumps need priming others not, doing a pump on a recent Guzzi it was essenntial to pack the pump, for this the recommended (& used) lube was Lubriplate, often used for engine rebuild lubing. I tried without, didn't prime & with which worked a treat.



After a build I remove plugs, prefill the filter as much as I can (easier to do on some engines than others). After filling the sump I crank the bike over, plugs earthed to the casings and removed, then spin it until I establish pressure

Given where you are, I agree with the others, get a gauge onto it and see what's happening. With no pressure on a running engine, especailly one that uses plain bearings, you can do a lot of damage in a short time.

I'd remove and earth down the plugs with a gauge on it. Turn it over (without the plugs in you don't place so much load onto the bearings) If no joy then I'd look at priming the pump as a starter.

Although as I've said I know sod all about that engine, just my own way of doing it & I'm no expert

John