1973 Triumph Tiger - High Oil Pressure In In-frame Oil Tank

sorry, just saw this.

im going to ask whether the oil tank is overfilled? if you top it up to just under the cap when its cold, the oil will expand and then spill out when you take the cap off. or is it actually blowing out under pressure?

the large diameter vent line from the breather fitting on the chaincase to the rear mudguard vents the crankcase through the drive side main bearing via the chaincase interior. the tank itself is vented by a smaller line that runs from a fitting on the spine tube under the tank, down the spine tube to a T in the big line that vents the crankcase.

if the big line from the breather fitting is plugged at the back end somewhere, then crankcase pressure can run up the little line under the tank and cause pulsing in the oil tank. perhaps that is what is happening?

triumhs dont wet-sump like nortons or BSAs, so excessive oil in the sump wont cause an overflow. the correct oil level on an OIF machine is high enough for you to get oil on your index finger when you stick it in the filler hole.