I'm glad you got that bike running well! Also hooked up the CHT. For my CT-1 it normally gets up to about 320 F/160 C when running at 55 or so for a while. That's at around 70 degrees ambient temperature. As far as the speedos being accurate, a year or more ago I attached to cell phone to the bike, with a speedo app. I found that the Yamaha speedo reads about 3 mph fast.

 I also just got a inexpensive borescope, and while I was using it for other things I popped out a spark plug and took a look inside the CT-1 cylinder. I've never had this cylinder or head off, and when I started working on this bike 3 years ago it had about 320 miles on it. I'm right at about 3,500 now. Does everything look okay?

imgur.com/a/5rJSWuY

Only one way to be sure & that's pull the cylinder. How does compression feel on the kick start. If it's going good i guess it's all ok. Too be honest, now i look at the marks i'd be a bit worried, like has it lightly seized etc. It's a bit like clear oil lines--what you can't see you won't worry about.

I appreciate the reply. It's actually running fine and has never seized that I know of. Feels pretty normal when I kick it over as well. Like I said, I just happen to have the borescope and  wanted to take a look. I have no idea what it should look like after 3,500 miles.

Didn't mean to worry you but was just my observations. Cheers.

Hot looking.

If 320F° is true, the piston is over 330F which is limit with limited lifespan.

c

In my experience, 320F CHT is on the conservative side in terms of safety and longevity.  

(For reference, Rotax air cooled aircraft engines consider 350F to 420F CHT to be the "normal" range if I remember correctly.)

260 f to 320 f is a normal operating cylinder head temperature for a Yamaha Enduro. If it were running an extended time up to 350 that could cause eventual damage. I just went for about a 10 mile ride. After going a couple miles at around 55 it runs about 305 f, then it cools down as I slow. When it's warmer out, say in the '80s, it'll get up to 315- 320 after several miles at 55. I do think my CHT meter is pretty accurate, comparing it to several infrared heat guns.

Well alrighty then.

..........If it were running an extended time up to 350 that could cause eventual damage....................

My experience disagrees with this part of your statement.  I did a lot of desert racing with two strokes...  hundreds of miles in deep sand, dry lakes...  and even a 24 hour endurance race.  Often in very warm temperatures.  I saw CHT's  in the low 400's all the time.  I even went two seasons (years) without a major teardown once and was still winning races.

A few years ago with one of my modified Yamaha 175's (later monoshock) I saw over 500F during a flat out run on a warm day on the El Mirage dry lake. GPS verified mid 90 mph speeds.  I DO NOT RECOMMEND PUSHING CHT THIS FAR!   That said, I consider low 400 CHT's to still be safe on an air cooled two stroke.  

One caveat with CHT is it reacts way too slow to warn you if say you're cruising along and, for example, make a sudden long full throttle run with a lean main jet.  If you ever notice the CHT starting to climb fairly rapidly, it might already be too late to stop a meltdown.