Oil Pressure Relief Valve Spring correct?

Ted Lang · Apr 30, 2015

I was recently reading a few strings on oil pressure relief valves. I bought my commando in 1974 and never inspected the relief so I thought it was time. I have no shims, and a very stiff spring that rattles when assembled. Using a stock copper washer (not shown), I need about 90-100 psi to get this to relieve. It won't go at 45-50 unless I back off the dome nut a lot. I can barely compress this spring with my fingers. Does this spring look right??

Oil Pressure Relief Valve Spring correct?

Thanks

guest76 · May 1, 2015

The spring looks right, although there should be a washer under the dome nut.

toppy · May 1, 2015

In his DVD Mick Hemmings says that the spring should be spring should be shimmed untill it is just free to move. If the seal washer is missing then there is likely to be unnecessary preload on the spring leading to higher pressure being needed to activate the relief valve.

pete.v · May 1, 2015

Although the spring looks to be the right one, it looks rather tired. Also, shims/washers applied are only needed to adjust pressure.

Towner · May 1, 2015

You need to ensure that the little piston is freely moving. Perhaps try fitting a second copper washer to get the right pressure.
90psi is to much IMHO.

Ralf

Rohan · May 1, 2015

How was this 90psi applied to test it ?
Hydraulically ?

Testing with compressed air will lead to wrong numbers.
(??).

Ted Lang · May 1, 2015

Yes, Compressed air--how did you know?? I thought it would be less messy. I also THOUGHT that the force balance would be the same with either air or oil, but I'll go the extra step and try oil this weekend. (Experience beats thought almost every time.)

The piston moves freely, even just by gravity, except just when exiting the bore, where you need to give a little tug.

Thanks for all the input that the spring looks right. I wanted to be sure I had the right parts before I spent a lot more time setting up to test the wrong parts or wasted money on a replacement I don't need.

watson rider · May 2, 2015

The only way to get this right is to plumb an accurate oil pressure guage into the system and adjust [by adding /deleting shims and or changing springs]the oil pressure until correct.I have never had to change the spring shimming has always worked for me [start with two]and aim for about 30-35 psi hot @about 100 k,s /hr or approx 3000- 3500 rpm.

JimC · May 2, 2015

I don't believe you have to worry about over-pressurization when the oil is hot. Preventing over-pressurization when the oil is cold is the purpose of the OPRV. Shimming the OPRV for ~ 65 psi when cold seems to be about right.

pierodn · May 2, 2015

Hi.
The spring is right but are you sure about the sequence of the parts.
Goes the spring against the cap and not into the body?
More, could you explain what the relief valve needs?
Ciao
Piero

Anonymous · May 2, 2015

Hi Ted Lang.
My oil pressure is 50psi cold and 25psi hot (oil gauge from rocker feed line).
Synthetic oil 20W50.

Towner · May 4, 2015

pierodn said:
Hi.
The spring is right but are you sure about the sequence of the parts.
Goes the spring against the cap and not into the body?
More, could you explain what the relief valve needs?
Ciao
Piero

Hi Piero,

the sequence seems to be correct. Normally there is a washer between spring and nut. Cold oil can develop a huge pressure. The relief valve is needed to avoid the destryoing of the crank oil seal.

Ralf

Oil Pressure Relief Valve Spring correct?

Ted Lang

guest76

Guest

toppy

pete.v

Towner

Rohan

Ted Lang

watson rider

JimC

pierodn

Anonymous

Guest

Towner

Similar threads