[Truckman]

the sensor is on the lower rear of the motor and the thread size is a metric pipe thread....good luck finding any kind of adapter at all.I also would steer clear of adding anykind of T or anything to the oil cooler lines as they are only a bolt and clamp/O-ring design which really doesn't like to be modified.honestly a cylinder head temp guage would be you best and most accurate way of telling engine temp on these motors as any condition to overheat the motor oil will be seen by a high head temp reading minutes before the oil temp guage starts to climb.ask any Kart racer and they'll tell you that an EGT guage is best then next best thing is a cyl. head temp guage for the air cooled motor.oil temp is a great idea for them but it's a pain the butt to pull it off the proper way and get an accurate reading.

 

[Truckman]

yeah.unscrew the spark plug and then put the head temp sensor in place of the plug washer and reinstall the plug.I used them for years on my karts and they are darn accurate...right up to the melting point of the piston reliable too as you can get digital head temp guages from Mychron or Digitron.they are vibration proof and water resistant but they make nice watertight covers to put on them.u can also get them with a TON of other options on the guage.speed,EGT,head temp,coolant temp,rpm,timers,backlighting,etc..they mount with a ball and socket setup similar to a RAM mount.

 

[Truckman]

here are some from Ebay.the lower end Digitron gauges have CHT and Tach. so you can also have a Tach. which is handy too.for the tach to work the lead is just zip tied to the plud wire at the head and it reads the pulses.these are auto turn off gauges too.
<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?Vi" target="_blank">http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0026605351</a>

<a href="http://cgi.ebay.com/ebaymotors/ws/eBayI" target="_blank">http://cgi.ebay.com/ebaymotors/ws/eBayI ... 0024976273</a>

this one looks to be a great deal.i'll find a link for the leads but they are about 20$ for both brand new.
<a href="http://cgi.ebay.com/ebaymotors/ws/eBayI" target="_blank">http://cgi.ebay.com/ebaymotors/ws/eBayI ... 0025316311</a>

the DT46K is what you would really want to use if you were buying new.
<a href="http://estore.websitepros.com/768505/Ca" target="_blank">http://estore.websitepros.com/768505/Ca ... ron+Gauges</a>

personally i would scan ebay for a few days and pick up a good deal on a used digitron tach.you can get killer deals on these as in the karting world guys are always buying the newest most high tech gadget and the "old" stuff is usually going pretty cheap.just use Kart racing for the ebay search or racing kart....there is always a good deal goin on.

 

[Truckman]

the sensors are expensive because it's a type K thermocouple.that's why i would lean towards the Kat gauges they are much cheaper if you find a deal on one.

 

[Truckman]

expect to see 250 degrees on a regular basis.my 100cc yamaha motors that turned out 18 Hp would run between 275 and 410 degrees depending on the weather.the honda motors are a low compression setup so the temps will be much lower,but would not be alarmed to see 250 on the gauge or maybe higher from time to time.