AMR oil pump cure

I have a bag of several OPRV's removed from covers of engines I have rebuilt. Most of them had no shims and the most I have found was two shims. I should also say that the majority of the pistons were stuck closed or would only open partially. It is very difficult to remove a stuck piston without destroying the mesh screen, so I usually replace the piston and body. That being said, The OPRV is to prevent over pressurization of the oiling system, which is not particularly likely with ball and roller bearing crank. Even with a new OPRV you are likely to see low pressure on a gauge when warm.

Final Update...I put in 2 shims in the OPRV. A 70 degree day, the motor starts in 1 kick, and the oil pressure climbs to 80 PSI. I'm calling it good.

So far, cold, the oil pressure jumps to 60 PSI. Then it drops off quickly as it warms up. Figure it drops to around 10 PSI with in 15 minutes of riding around city streets in 80 degree weather. That's 10 PSI at idle. Seems like too big a drop for a fresh motor.

seattle##gs said:

So far, cold, the oil pressure jumps to 60 PSI. Then it drops off quickly as it warms up. Figure it drops to around 10 PSI with in 15 minutes of riding around city streets in 80 degree weather. That's 10 PSI at idle. Seems like too big a drop for a fresh motor.

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That's about what my 850 does. If you go for a high rev run up a mountain or a longish crawl in a traffic jam in hot weather, the pressure goes to around 5 at idle.

10 lbs at idle is real good.

Add an oil cooler if you want to keep your oil pressure up. Nortons have been running happily with 5 psig oil pressure when hot from nearly time immemorial. The anxiety occurs when one adds an oil pressure gauge.

Oil pressure does not prevent metal to metal contact ..... oil film strength does ..... oil film strength is of the order 110K psi, oil pressure simply keeps fresh oil in the spaces.

Slick

10W/60 oil will reduce the oil pressure on start up and keep it up for longer as the oil heats up. As @texasSlick says the oil film thickness is key, oil pressure is just an indicator that the oil film thickness is likely to be good but it is not a direct reading of the oil pressure within the oil dam created inside a plain bearing. You need to be a laboratory to be able to take direct readings of oil film thickness and pressure within that oil film.