English French German Italian Spanish

Rebuild oil pressure

Submitted by david_evans on Tue, 12/05/2015
Forums
Commando

I've taken the precaution of fitting an oil pressure gauge after my rebuild. I have new big end shells on a reground crank, yes there is a seal inside the timing cover and a new grommet on the pump. Morris V twin 20-50, initial start up cold is good with about 50 psi and settling down to tickover at about 35psi. 45 mins of running in driving (below 4000rpm) and the cruise pressure at 3500rpm is about 25psi and tickover, zero. I might have a rubbish gauge but thought I would get better than that. I serviced the pump about 3000 miles ago and the return flow is good. Thoughts?

Submitted by phil_hannam on Tue, 12/05/2015

Permalink

Somewhere on this website there is a similar thread about oil pressure and where best to measure it from. The Commando oil system recirculates a proportion of the flow. Would this affect the indicated pressure?

Plan B......fit a 12 start pump worm/gear. You can get these from the same suppliers as hen's teeh.

Submitted by tony_harris on Tue, 12/05/2015

Permalink

I think if you take the feed off the rockers it's less than off the back of the timing chest. My 750 engine(on 20/50) is about 60psi cold 50psi hot but about 35/40 psi below about 1500rpm. This is taken off the rocker feed on the cylinder head.

Submitted by david_evans on Wed, 13/05/2015

Permalink

The pressure in a system is the same throughout the whole system unless there is a pressure reducing valve fitted. This means that the pressure whether it is measured at the back of the timing cover or the rocker feed bolts is the same. If you restrict the pipe, the flow will be reduced but the pressure will remain the same either side of the restriction.

Submitted by tony_ripley on Wed, 13/05/2015

Permalink

Previously david_evans wrote:

The pressure in a system is the same throughout the whole system unless there is a pressure reducing valve fitted. This means that the pressure whether it is measured at the back of the timing cover or the rocker feed bolts is the same. If you restrict the pipe, the flow will be reduced but the pressure will remain the same either side of the restriction.

Dave,

This is only true in a static system where there is no flow. If you have flow then all bets are off. Consider the case where you have a high pressure feed pipe with a small hole feeding to a low back pressure system. If there is nothing to restrict the flow in this system it can be close to atmospheric pressure.

Tony

Submitted by david_evans on Thu, 14/05/2015

Permalink

Hi Tony,

Thanks for drawing my attention to the link, it is good revision. I'm not too concerned by the low oil pressure and I don't think the gauge is particularly accurate at low readings. Blatting along at about 50-60mph there is about 20 psi and as long as there is flow of some sort at tickover I'm not going to loose any sleep over it. I know that the engine bottom end is as good as it can be for a 45 year old bike. I wouldn't think an oil cooler is a worthwhile mod in this climate as I'm keen to get the oil up to a working temperature. I might investigate an oil temp gauge just for interest.

 


Norton Owners Club Website by 2Toucans