Inline temp gauge?

What is it you are really trying to accomplish?

If the idea is to catch the fact that your engine is overheating then you will need to be able to read the gauge while you are riding. This would imply a gauge mounted on the handlebars.

Temperature gauges will come in two basic types: Electrical and mechanical.

The mechanical gauge will not require any electrical power but they will either be mounted directly to what you are measuring or there will be a small tube that connects the sensor with the gauge. These tubes generally can not be shortened so you may need to tuck 6 feet of tube some place.

I would not recommend drilling any part of your engine to install the sensor. Instal a "T" in a hose, insert the sensor into the T.

Electrical gauges need power. There are lots of electronic types that could run off a small battery but I have my doubts that they would survive long on a dirt bike. I ride enduros and I have tried a couple of times to mount a cheap kitchen timer to my handlebars. They have generally lasted about 10 miles before they had their brains shook loose.

If you just want to occasionally get a reading and can stop to look at the gauge then I would recommend getting one of those small thermometers that you poke into a steak and sliding it into the fins of the radiator. After you have stopped for a second and the air flow through the radiator has stopped it will get a reasonable reading of the water temperature.

Rod

here ya go
http://www.eddie-sanders-racing.com/oscmax/index.php?cPath=20_36

If you want to protect the engine in the event of a water pump failure then the only place to measure the temperature is at the engine. If the water pump fails the radiator and hoses will cool down considerably as the engine overheats.

The best thing to do is to measure the cylinder head temperature. You can use a thermocouple sensor that is like a large ring terminal that mounts under the sparkplug. A mechanical gauge can be self powered from the thermocouple but I doubt that the mechanical gauge would survive the rigors of off road.

Here is a website that details mounting such a device on a "paraglider", which has a similar engine setup: http://www.aerocorsair.com/id62.htm

If you could do the same thing except use a digital gauge that has no moving parts it might survive on the handlebars.

Rod

some people claim that the CHT should not be greater than 220ºC after some seconds at full load, like the biggest strait, or up hill... after that the engine will start to overheat and start to loose power...

Any measurement you make is going to be a "relative" measurement. That means that it will go up or down according to the temperature of what is critical but it won't be the same value. In other words, the temperature inside the cylinder is going to be a lot hotter than the temperature anywhere outside where you can easily measure it.

In this case, realtive is all you really need. Make note of the temperature when you are riding normally and the bike's cooling system is working properly. Imagine that you had a gauge with no numbers on it and you just drew a green band in the area that the needle is normally. Then you draw a red line to the right of that. It doesn't matter what number is associated with those marks, what matters is if the bike is running normally or not.

Rod

Why not just use an EGT gauge ? It is the ultimate in melt down prevention !