Pat, I owned a '71 BSA RocketIII which I bought new(as you know, eventually to become basically the T160 Triumph later in the '70s), and I never had much problem with this cooling issue the 5 years that I owned it. My friend Phil had for many years until very recently a T150, and he never had much trouble in this regard either.
I do remember that the valve clearances on the middle cylinder were to be adjusted very slightly "looser" than the outside cylinder's clearances however, as #2 did run slightly warmer than the others.
The reason all the old A75 Rockets/T150/T160 had those oil-coolers sitting just below the gas tank was to cool #2, and as far as I know they did a pretty good job of doing just that.
These bikes raced with pretty good success back in the late 60s and early 70s, and as I remember even though this was the "theory" about that middle cylinder at the time, I don't recall BSA/Triumph having a particular problem with this on the track during that time either.
But, if you have torn down many of these engines in the past and found this problem to be true, I will defer to your experience.
Last edited by Dwight; 08/22/2007 4:20 PM.
