Hello all! Having a strange oil pressure reading that I can't quite get my head around. Read Dan1950's threads about his OPRV and weird oil pressure after rebuild, and while I'm having a similar problem, it's not quite the same. 1971 750 Commando. Just rebuilt the motor, new JS ultralightweight longer rods n pistons bored 40 over, new STD big end shells, crank polished (not reground) new AN roller main bearings, original cam, bushes and lifters, removed timed breather disc and spring, blocked off breather port, went with NYC norton sump breather. AMR modded OPRV discharge and put seals in the oil pump along with the check ball and spring in the timing case. New seals all around. Head rebuilt concurrently with kibblewhite black diamond valves and standard springs, new rocker shafts, original rockers.
Bike runs like a top! Trouble is, oil pressure drops off after a long hot ride. I live in a place where it is generally really hot in the summer (+100 highs, generally for a month or so) and I'm wondering if my pressure gauge acts more like a temperature gauge. Cold oil shows 60-65 psi, first 20-30 miles into a journey shows oil pressure around 40-45psi. Then oil pressure usually drops off around mile 30 or so to 15-20psi as the oil in the tank heats up to really hot. Usually cruising at 70-80 using the rest of the tank of fuel it hovers around 15 psi. Stopping in traffic, the pressure at idle when reeeeel hot shows like 0-5psi, which i'm told isn't all that unusual. Comes back up to 15-20 when you get rolling around 3000-4000 rpm. Oil is returning to the oil tank normally even when at hot idle, showing the 0-5psi. ORPV is new from andover, 2 shims, pulled and reinstalled to ensure no binding, everything is smooth as silk.
This is the first bike ever that I've put an oil pressure gauge on, so other than reading here, I've never known or cared what the oil pressure was in any of my 5 other vintage bikes. My CB750 has an oil pressure light, and that's up town for me! Am I worried over nothing, as there is adequate flow returning, and over several hundred miles there's been no damage? I'm about to do the 500 mile oil dump and I'm thinking about pulling the timing cover to check the oring on the oil pump, but... if it was gone or shot, wouldn't there be like zero oil pressure all the time? Mexicomike and marshg have mentioned that the oil pressure gauge is... superfluous at best. Should I chuck it?
Further oddity- took the bike up our mountain pass to 11000 feet this weekend and when we got up where it was colder, the oil pressure went from 15ish back up to 30-35ish! I have no idea what that means. Maybe install an oil cooler! Or just ride in winter....
Bike runs like a top! Trouble is, oil pressure drops off after a long hot ride. I live in a place where it is generally really hot in the summer (+100 highs, generally for a month or so) and I'm wondering if my pressure gauge acts more like a temperature gauge. Cold oil shows 60-65 psi, first 20-30 miles into a journey shows oil pressure around 40-45psi. Then oil pressure usually drops off around mile 30 or so to 15-20psi as the oil in the tank heats up to really hot. Usually cruising at 70-80 using the rest of the tank of fuel it hovers around 15 psi. Stopping in traffic, the pressure at idle when reeeeel hot shows like 0-5psi, which i'm told isn't all that unusual. Comes back up to 15-20 when you get rolling around 3000-4000 rpm. Oil is returning to the oil tank normally even when at hot idle, showing the 0-5psi. ORPV is new from andover, 2 shims, pulled and reinstalled to ensure no binding, everything is smooth as silk.
This is the first bike ever that I've put an oil pressure gauge on, so other than reading here, I've never known or cared what the oil pressure was in any of my 5 other vintage bikes. My CB750 has an oil pressure light, and that's up town for me! Am I worried over nothing, as there is adequate flow returning, and over several hundred miles there's been no damage? I'm about to do the 500 mile oil dump and I'm thinking about pulling the timing cover to check the oring on the oil pump, but... if it was gone or shot, wouldn't there be like zero oil pressure all the time? Mexicomike and marshg have mentioned that the oil pressure gauge is... superfluous at best. Should I chuck it?
Further oddity- took the bike up our mountain pass to 11000 feet this weekend and when we got up where it was colder, the oil pressure went from 15ish back up to 30-35ish! I have no idea what that means. Maybe install an oil cooler! Or just ride in winter....
that was a 2.311 std size, it was ground though, normally have .002+ , we generally like to grind to suit the new measured bearings in the torqued rod etc .
