Oil Pressure, Carb, Saving Paint and Chrome Q and A

"An old rule of thumb for oil pressure is 10lb per 1,00rpm"

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by Pexels/cottonbro

Oil pressure issues

Q: Hi Keith. I have an oil pressure issue. I took a 1974 Triumph T160 engine and had it rebuilt with the only changes being new Amal carbs, new clutch, new 3-into-1 exhaust, new camshafts and lifters, Boyer ignition, new pistons and bearings and rings and a new high pressure oil pump. The bike runs fine for the first few miles then as you slow down to an idle to stop the oil pressure drops to zero. Add a little rpm above idle and it climbs back to a normal pressure (about 20lb) then reaches 40lb while running highway speed. The engine is mounted in a Trackmaster oil-in-frame unit. I read somewhere that the Triumphs factory-made with these oil tank in frames had similar scavenging issues. What is my oil pressure problem? How do I solve it? Thank you for your time.
Rick Rahm/via email

A: My 1974 Triumph T150 behaves similarly when the oil is hot. At idle the gauge drops to nil, but blip the throttle and it climbs instantly. An old rule of thumb for oil pressure is 10lb per 1,000rpm, so while 40lb at 4,000rpm may seem low, it’s not a disaster. Another test is how long it takes for the low pressure light to come on after you kill the engine with the kill switch. If it comes on instantly you most likely have a problem with the rod main bearings leaking out too fast. Another possibility that I just faced was the condition of my oil pressure gauge. The plastic face was crazed from sun exposure and it started weeping the fluid used to dampen the needle. I replaced it and the new gauge shows better readings at all rpms.

Carburetion question

  • Updated on Oct 8, 2021
  • Originally Published on Sep 30, 2021
Tagged with: 10lb per 1000rpm, carb jets, chrome, marring, original paint
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