Originally posted by John Healy:
I wish this was a new problem, but it has been with us for more than twenty years.
Kommando is right that production of these seals has moved to the far-east, but it is not the only problem. I think if you check, all of the seals available are made in the far east, including the one I prefer: Pioneer brand (which was o.e.m. to Triumph).
I made the tool above when I first started using Morgo rotary pumps, as they can easily invert a seal if you are not careful. I would check all of the brands I could get my hands on and finally settled on Pioneer. They will typically hold 50% more pressure than the best competitor.
We have tested some seals that would invert with less than 100 pounds of pressure.
Now, sometimes it is not just the seals fault. There can be other factors that can push the seal beyond its limits:
a. Oil that has a viscosity greater than was specified by Triumph for a given season of the year will strain the seal beyond its limits, especially at start up. Unless you have a good reason, and fully understand what you are doing, using oil with a viscosity heavier than Triumph recommended can cause seal and other problems.
b. A oil pressure relief valve that is sticky or stuck closed.
c. A crankshaft whose end has been turned undersize.
d. Too little rod bearing clearance.
e. Too little side clearance on the rod.
f. Using a Morgo rotary pump without making the required modifications AND increasing the clearance on the rod bearing shells.
h. putting the seal in backwards.
i. cutting the seal's lip when the timing cover is offered to the motor.
j. Blocking the oil passage to the tappets, as you do when you install a Morgo long rod 750 cylinder and don't make accomidations for the oil that was by-passed to the tappets. Typically doesn't happen by itself, but in combination with one of the other things on this list.
k. Blocking of one of the oil pressure by-pass holes. i.e blocking the oil hole from the presure relief valve so that you can run a breather off the timing cover without making accomidations to redirect the oil out of the pressue relief cavity.
l. Some combination of the above.
m. I am sure I am forgetting something!
In my experience you have a 50/50 chance of damaging the motor when the seal fails. It all depends on a lot of factors. I can only relate to you that people who race Tridents (albiet, different oiling system) instruct the rider to stop if the oil pressure falls below 70 pounds.
Typically, when the pressure falls in a Trident it is telling the mechanic that the center mains are begining to wear, which will starve the rod bearings and lead to ruining some very expensive parts. When your seal inverts you are starving the rod bearings in a twin.
SDA stands for Sung DA a Taiwanese seal manufacturer. I haven't tested one lately, but the last ones I tested inverted at about 150 - 160 pounds cold, and less once I heated up the aluminum body of the tool. The typical Pioneer inverts at over 200 pounds.
In all fairness I must tell you that I sell Pioneer seals, but those that know me will tell you that I don't push any of my products unless I believe there is a compelling reason to do so. So you will never see me promote a product I sell in Vintage Bike, this site or in any TIOC information.