Adventures with oil pressure

I think the Triumph is trying to make me crazy. After closing on Sat., I was running it to check on the fuel system and the loss of oil pressure. Adding the extra discharge hole in the carb and enlarging the existing one helped, but it wasn’t anywhere near enough.

The oil pressure was again at 50 psi, enough for the crank to live but not enough for running with a load. I opened up the accelerator pump orifice and rechecked the running….better but still not enough. A couple of ignition timing changes didn’t seem to make a difference either. The oil pressure was a couple of pounds lower.

I thought this might be a good time to check the blower belt tension and since the motor was warm, I made certain the tension was on the snug side of spec by tightening it up slightly. I ran the motor again and damned if it didn’t start leaking out of the back of the primary, near the sprocket shaft.

I drained down the primary to the level plug and loosened the blower belt and after cleaning it all off ran it again and it quit leaking. All I can figure is that the tighter belt deflected the crank and caused the seal to not keep oil and/or crankcase pressure in the motor, although the outer crank seal didn’t leak (Japanese seal?).

At this point I checked the flow into the pump through the line and then removed the screen over the inlet of the line. No improvement. I took out the pressure relief valve and increased the tension on the spring, but no help there. At that point I took off the timing cover and re-evaluated the oil pump.

The pistons looked a bit more scored than I remembered them and there was a fiber in the check ball area of the pressure side of the pump. I went to the box of parts from the other motor and compared the pumps. The old parts box pump looked better and after cleaning, I installed it.

After start-up I watched the gauge go to 105 psi, and then the pressure relief popped off and the pressure stabilized at 90psi. At this point, the throttle response seemed the best it had been yet. So now we are going to enlarge the original discharge hole, add another, and watch the blower belt life at the reduced tension to in turn reduce crank deflection.

Why oil pressure and running may or may not be related makes as much sense as blower belt tension and a clutch shaft oil leak. Ya gotta love it! I think I will move the tank up to right below the pipes and carefully heat shield it to increase the head of potential pressure at the oil pump, and special care will be needed to deal with the cap at that point.




One Comment Add yours

  1. Bill!! I love your blog, I just stumbled upon it…Very Interesting, the bike looks amazing. If you have a chance please check our blog at I am very interested to hear more about the bike. I am not gonna make it to the lakes this year as I have a broken ankle, my partners will be there with their vintage bikes. m-vf 500cc triumph a-vf 250cc triumph cub. The cub has 2 records and the 500 is looking for its first after 3 years of hard work. I am building a pre-unit for APS-PF 650cc. Hoping to get it done this year or begining of next year for some El Mirage runs. You are a major inspiration-keep up the good work
    -Chris Hamilton

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s