Adding an Oil Thermostat to Your BSA/Triumph Triple

| 6/10/2019 8:29:00 AM

Two readily available thermostats for your BSA/Triumph triples: the Madigan (left) and the Tru-Cool (right)

BikeMaster logoThe Triumph Trident and BSA Rocket III were among the first production motorcycles fitted with an oil cooler. Due to the extra cost, no thermostat was fitted. For long, fast runs, that probably never mattered.But as these bikes have become used more for pleasure than utility, shorter, slower rides are more the norm. Because of that, the oil often doesn’t reach high enough temperature to boil out the condensation that occurs when the motor is warming up. It also takes longer for the motor to warm up with the oil constantly circulating through the cooler. Neither of these factors are good for the long term life of the oil or the engine. Fortunately oil thermostats are in widespread use in the trucking industry as regulators for transmission coolers. Also, triple specialist David Madigan has designed a thermostat specifically for the BSA/Triumph machines that incorporates a special feature, a feed pipe for the rocker boxes. We’ll show you how to install either the commonly available transmission thermostat or David’s specialized one in this How-To. A detailed explanation of the function of these thermostats is well beyond the scope of this article. For a good report of the function of both of these designs, refer to, where you can find a report written by Richard Beard, who was present at the creation of the original cooler for the English triples. The Tru- Cool was sourced via Amazon, while the Madigan thermostat was purchased directly from David Madigan. The Tru-Cool was about $47 shipped, and the Madigan was about $80 with Priority Mail shipping paid by check. PayPal adds about $2.50.


1.) As always, disconnect the battery. Iput a rubber cap over the positive connector to prevent any accidental connections while working on the bike. Disconnect the gas lines from the petcocks to the carburetors too.


2.) We begin by removing the gas tank; the oil lines we need to accessare under the tank, along the top tube. You’ll need a 1/2-inch socket and ratchet to remove the bolts holding the tank in place. An extension will be useful in removing the front tank bolts to avoid interference with the oil cooler.

7/14/2020 2:40:30 PM

Well here's another fine mess I made for myself. David's email address is, not designs. I regret the error.

6/13/2019 6:20:40 PM

Well it wouldn't be a HowTo article if I didn't forget something, this time it was the fact that the T160 has a different rocker feed than the the T150 and Rocket 3. I'll let David Madigan, the man who made the T150/Rocket 3 specific cooler, give the details. From his post on "I would like to add that T160s have a dual rockerfeed line coming off the return hose which presents a problem with my thermostat. There is not enough room to add another pipe on the cap for the two lines so you would have to use T150 rockerfeed line or my machined rockerfeed with the AN-04 cap on the thermostat. 45 degree hose ends on the feed line from thermostat to rockerfeed lift the thermostat above the head. With the Tru-Cool, the dual tee has to be mounted in the return line before the thermostat. DM"

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