Tuesday, June 19, 2012

Temperatures and Airflow

While I'm still very happy with the performance of the VTR, one thing concerns me (a little); overheating. There were times, during my previous commute, where the water temperature, as indicated by the dash gauge, crept towards the top end of the indicator zone (without entering the red portion). The ambient temperatures, at the time, were in the 70s (F). My immediate concern was what was going to happen when ambient temperatures reached into the 90s (F) or higher.

The obvious thing was to ensure that the thermostat was functioning properly. It is. The second concern was that the radiator was free of external debris (that is, the fins are not clogged with dirt or bugs or the fins aren't all bent). It is. The third concern was that the radiator is not clogged internally. It doesn't seem to be. Fourth, ensure that the coolant hasn't broken down and is up to the job. It is.

After all of those considerations, it seems that airflow, or lack thereof, is the key component to keeping the VTR cool. The bike does have a thermostatically controlled fan. However, it's hard to hear if it's running (when the motor is hot). I know some owners have retro-fitted a manual fan switch so that they can control when the fan operates, if they think the thermostatic switch has failed or if they don't want to wait for it to trigger the fan. Recently, I've been in some traffic situations where having a manual fan switch would have been beneficial. My wife and I recently rode thru some of Chicago's northern suburbs. The ride 'out' was relatively slow due to traffic and traffic signals. There were several times when I was keeping a wary eye on the temperature gauge. However, the ride home, following the same streets, had less traffic and we managed to time the traffic signals so that we were stopped less often. The needle on the temperature gauge never moved above half-way (the ambient temperature was higher, too).

So, it would seem that air flowing thru the radiator, regardless of ambient temperature, is important in keeping the VTR cool. My current commute is very conducive to constant movement. That is, traffic flows quite well and quickly thus aiding air flow thru the radiator. However, it wouldn't take much (an accident or a freight train - there are several grade crossings on my commute) to turn an eight mile (twenty minute) ride into a coolant boiling catastrophe. Perhaps a manual fan override switch is in order, now that Summer is here (or will be in a few days). Stay tuned for another "How To" post...


  1. I read you post re overheating. I've been using my VT here in Sydney and it does get warm in traffic, but the highest it's gone all week is about three quarters up the temp scale. Bear in mind it's Winter here at present! I wonder what will happen in our Summer, that can get very hot! Cheers William.

  2. Hi William, thanks for the comment and I'm sorry it took so long to respond. I've had various other VTR owners tell me that the Honda temperature gauge is notorious for reading improperly. I would make sure that the system itself is sound (clean radiator - inside and out, good t-stat, good coolant, good fan motor and good thermo-switch). If you're not sure about the thermo-switch, you can run a jumper to ground (earth) with an in-line, single-pole, single-throw switch. Then, you can activate the fan when you see fit. I've heard it's best NOT to run the jumper to the negative battery terminal, choose a grounding lug on the frame (that the wiring harness uses - there should be a few). Good luck and keep us posted.