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Oil not returning

Submitted by mark_tomblin on Sat, 18/02/2023
Forums
Commando

Hi

After a lot of work I have now sealed my cylinder head and stopped the dreaded smoking from the valve guides.

I noticed earlier that my oil was only returning at a trickle so £240 later I purchased a new oil pump from the NOC shop

When I put this on, at first I had a little trickle of oil - but now none!! I have drained the sump I got about 5/8 of a pint , then filled the oil tank with fresh oil, started the bike-  the oil is being returned via the engine breather . I pulled the pipe off on the return side at the engine and no oil is coming out the pipe, plenty is coming out of the breather so the pump must be filling the crankcase but no return? Any help would be most welcome before I push this damn bike into the cut ...

all the best

Mark.

Submitted by richard_payne on Sat, 18/02/2023

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Is the gasket the correct way round ? To be honest, even knackered oil pumps usually give a fair return...could there be a blockage on the pickup side ? Silicone in an oil gallery or similar ?

Submitted by mark_tomblin on Sat, 18/02/2023

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I will investigate tomorrow I did not need to remove the gasket or used any silicon but it’s worth looking at cheers Richard.

Submitted by peter_shand on Sat, 18/02/2023

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Did you change the oil filter? it takes a minute or so to for the return to fill the filter and then be seen at the tank. Have the oil pipes been transposed on the oil filter mounting head? the oil filters have a flow and return side so pipes on wrong can halt the flow,  

Remove the oil pump and blow through the ports in the crankcase with compressed air to prove clear. Does the engine have the large sump plug/strainer? if so remove and prove clear    

Make sure the feed pipe is primed (slacken the oil junction block bolt till oil weeps out)

If an anti wet sump valve or tap is fitted, remove it. 

Hi Peter the oil filter has not been touched,I have taken the pipe off at the engine tomorrow I will take the pump off and check for obstructions and work through all that has been suggested thanks for your suggestions cheers mark.

Submitted by ashley_cutler1 on Sat, 18/02/2023

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Return gallery at the junction in the RH crankcase worth checking out, it blocks at the point near the grub screw. 

I am of the mind that the new pump is faulty as the oil came out of the hole with the grub screw it flowed ok I removed the plugs and turned the engine via the kickstart with the block and grub screw replaced after a lot of turning over a dribble came out of the block but the breather was really chucking it out back into the oil tank so the bottom end is getting flooded with oil . I was hopeful that this would be a quick fix . 

Submitted by david_comeau on Sun, 19/02/2023

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Lack of sump filter allows severe degradation of scavenge side return . Your symptoms are known within this last 750 NHT family.

Submitted by philip_hannam1 on Sun, 19/02/2023

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I would be checking for the feed and return pipes being replaced incorrectly somewhere in the oil system. It is very easy to do especially if the bike has an oil filter fitted. When I purchased my second Commando the return oil pipe was connect to the breather on top of the oil tank.

Submitted by andrew_mackenzie on Sun, 19/02/2023

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As the crankcase appears to be receiving plenty of oil (5/8 pint mentioned), doesn’t that suggest the oil feed pipes are correctly connected?  If the drillings from the scavenge oil pick up to the oil pump flange are unobstructed, there is surely no reason why the scavenge pump suction could not draw the oil through and return it to the tank?  That would be the focus of my attention.

That’s what I think Andrew.

I know that the thing is piped up right and it is filling the crankcase up with oil, right up to the breather level.it’s the scavenger side of the pump that’s the problem I have another old one that I will try if that works better I will send this new one back it was from the NOCShop and it is supposed to cover all models but I think it’s possibly faulty . I am at a loss if it’s not .

So fingers crossed.!

Mark

 



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