Honda Spree and Elite 50 Forums

I bought the TTO Digital Temperature Gauge Made by Trail Tech. Ordered it from one of the suppliers on this site. The instructions say that to install the sensor you have to remove the crush washer from the spark plug and replace that with the sensor and reinstall the spark plug. I don't think the sensor and it's connector will fit in the spark plug well. And I don't like the idea of removing the crush washer. It is there for a reason.

Has anyone installed a gauge similar to this? Did you have any problems with it? Would it work if I install it under a bolt on the head instead? Will it be accurate or react quickly enough to be useful if I do this?

The other problem I see is that the lead is too short to install the gauge where it can be seen while riding. I was thinking about installing this gauge permanently. I guess I could splice the wires and extend them.

Maybe it would be better to use this gauge as a "test and tune" device and get the jetting where I want it and then take it back off until it is needed again.

From my understanding the sensor takes the place of the crush washer otherwise the sparkplug would not be at the right depth. The leads are short b/c it's designed for a dirt bike. They make extensions for them so you can mount it further away. I would not think it would be as accurate mounted on a head bolt. I would definitely use it how it describes. I know many people on here use them and say they work well.

not as accurate under head bolt read link below
http://hondaspree.net/wiki/index.php5?t ... nic_Meters

Mounting on the head bolt can be a lot lower than the spark plug. You are correct in thinking you have to remove that washer that comes with the spark plug. Be careful to not "cross thread" the fitting or the hole. Those temp send units need to be cleaned and inspected each time its taken off.

EXCELLENT info thanks guys.

I think I'll do a temporary install to get the jetting right when my exhaust gets here. I'm hoping it will get here today.

THREE questions I should have asked :

The important one : What is the peak temperature that is acceptable?

What is the normal temp for cruising at a variety of throttle settings?

How do best measure max temp? Is a few miles at full throttle what I need? Or should I find a long uphill that puts the engine under max load? Or will just a mile or so under full throttle be enough for a valid test?

As stated by others...180-315 degrees seems to be about right.


I tested 49 and 70cc engines and the top of the head was about 300F after idling for 13 minutes.

I found these two quotes on another site. I'm assuming 320 degrees is a safe max. I also read that 400 degrees is possible on properly tuned race engines.

Can I assume that an occasional 350 degree peak wouldn't kill a stock street engine?

I hope those more knowledgeable that I ( most everyone) will add their experiences.

your fine at 350 over 400 is bad under 300 is running a bit rich

on occasion mine hits 364. Didn't want to run without the crush washer on the plug so unscrewed it, put the temp wire on then put the washer back. Have not seen any ill effects from this way of doing it. but not out to get every ounce of power from the bbk.

not as accurate under head bolt read link below

Hey, thanks for looking into the wiki!

Intent with the comparison was to show a clear difference between the plug and a head bolt. Many tuners give numbers from the spark plug. If these temps are applied to the head bolt location, the user may have a false sense of security, as the readings are lower and did not reflect spikes the plug location captured. So back in that day, we had interesting threads, and temp postings, but with varying temp sensor locations and varying 'safe readings'. That is what fueled the comparison. Sure enough, there is a difference, thus members should make sure to know the source of a reading when mapping to your own situation.

-- Disclaimers
Even with a CHT on the plug, its not fool proof. Some setups have generated a piston failure faster than the head temp/meter and rider can compensate for. Starting quite rich and backing down never hurts. Several tuners have pointed this out along with CHT's are not mandatory.