Ask The Pro - Answers - 2005 Honda ST1300

Too Cool

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I have had a problem with my 2005 Honda ST1300 since the middle of last winter. One day, I noticed that it did not warm up as quickly as it normally does. From there, things got interesting. After hundreds of miles of riding, I realized that the engine temperature was directly proportional to the outside air temperature. On a cold day, the coolant-temp gauge would never read more than one bar. On a really cold day, it would not show any bars at all. During the summer it seemed to be fine, going to three bars on the gauge and staying there. After investigating further, I think the thermostat is stuck in the open position. Two different Honda dealers have checked the bike, and neither could duplicate the problem. I know it hasn't gone away because of the extended time the bike spends warming up at fast idle, so I'm wasting fuel. It's still under warranty until September of 2009. Can you help?
Mike Bracken
Knoxville, TN

A Sure. We pinged Joe Zulaski, headman at, the worldwide Honda ST1300 owner's forum. It seems he's heard this story before: "There have been many reports of stock thermostats getting stuck in the open position. A lot of the riders find contaminates in the thermostat and suspect the foreign matter is coming from the anti-freeze or from some sort of internal coating that flakes off and clogs the thermostat."

Zulaski says that while there's no definitive evidence as to a specific culprit, the solution seems to be flushing the system and replacing the existing anti-freeze with the type listed in the Honda shop manual, along with a new thermostat.

"Many riders have gone to an aftermarket thermostat from Turbo City, thinking that the original part was to blame," he says. "We have received no reports of those getting stuck, whereas we have received reports from some riders who have replaced their thermostats with another original-equipment part, only to experience the same issue later. Unfortunately, in many cases, neither the Honda dealership contacted nor their rep seemed to be of much help."

Start with fresh coolant and a new thermostat-don't forget fresh gaskets-and everything should be copasetic in the cooling department.

Some Honda ST1300 owners have reported cooling issues caused by thermostats sticking in the open position.