Do they tend to run pretty hot?

Mine has stock aribox / filter / exhaust ect, the only difference in the carb settings is that I have dropped the needle one notch - simply because it runs best in that position. Pug colour looks good but it does feel very hot after a run. Ought i to up the needle back to where it "should" be to keep it a bit cooler.

I have had other 2 strokes over the years - and stil have my H2 Triple but none of them seem to get so hot to the touch as the DT.

It is running Rex Speedshop ignition so no opportnity to change the timing.

You can slip a small shim / washer under the needle to effectively set in a half step clip position .
I think Sudco list it as a spare part .
If you're concerned about high engine temperature , you might look at buying a TTM temperature sensor ,
to check head temperature . There are a number of threads covering this .

Not managed to find much about a TTM tems sensor - managed to find one thread on this forum. TTM sensor seems to be a sensor that is in the form of a washer that fits under the spark plug - neat idea. However I cant find anything on the web about them. UPDATE: Managed to find them, they appear to be called Trailtech Cylinder Head Temp Gauge.

I was thinking, my multimeter has a temp sensor attachment - basically a thermistor on a length of wire, so I could use that to give ms some idea, but what sort of temps are we talking about that are reasonable.

On the thread that I did find, 400 deg c was mentioned using the TTM sensor so is the the sort of temp I should not be exceeding ?

No idea what you read...  400 degrees F (fahrenheit) is likely what it said though, not C.

I suggest getting a correct cylinder head temp gauge that uses a thermocouple under the spark plug...  trying to "get close" with another method will give you data that won't be comparable. 

Head cools off quickly and temperature varies widely depending on where you measure. 

If you want to see roughly how hot things are an IR temp gun or your method should work...  I just wouldn't tune by it. 



 

I have the trail tech on my dt 360 and the highest temp that I have seen is 370 degrees.

There are literally dozens of threads mentioning the Trail Tech gauge and temps. Search is a bit buggy right now. Here's one of them with Enduronut's recommendation.

yamaha-enduros.com/index.php/forums/1968...-cylinder-head#53719

The head does cool quick so using an IR heat gun or other method to measure after stopping won't give you the peak temp under load... and also if something is off, you can have engine failure before a CHT gauge will register the excessive temp. Having a gauge is a good piece of mind though.

Thanks for all your words of wisdom and the link.

Of course I mean 400 deg f..............

I used to worry about head temp going back to my first bug build with a stock case where #3 had a hot spot, before it blew up and I went to a race case. Temp on head was always between 250 and maybe ~350F on a hill on a hot day, so I always thought I was ok because oil doesn't coke until ~400 (never went above 230F) and aluminum doesn't melt until >1200F

With these bikes, after burning a hole in my DT360 my first one where I new less than nothing and everything was wrong, I have decided to ignore temp and to instead make sure that lube pump output and adjustment is at spec, no air leaks, that jets are at least as rich as specified by Yamaha and that timing and plug heat range are proper.  Then I just ignore temp and ride to my hearts desire! 

Msavitt - now that has got me thinking.
Over the years I have had quite a few 2 strokes - several 250 and 301 MZs to which I have fitted home built expansion chambers to, thrased them to death and not one seizure.
I have had (and still have one) Kawasaki Triples, all of which have been fited with expansion chambers, different carb setting etc, again not one of them has seized or blown.
The DT is not making any pre ignition noises, meets my expectation in terms of performance, and the plug colour (which is what I have always gone by) looks great.
Perhaps I should just ride it and not worry........