Hot exhaust - investigation

[scooble]

after replacing the faulty temperature sensor, it now reads something a bit more reasonable.

After running the engine for a minute or two, I quickly blipped the throttle, and the engine would bog down initially and then spit out black smoke and hot carbon from the tailpipe.
I then noticed the rear right exhaust glowing orange - Eeek!
shut down the engine and allowed to cool.
I suspected bad jetting, so wipped off the carbs ( yeah right - so much easier on my KR1), anyway, the front mains were 115 and the rears 118 (which I assume is Jap spec jets), therefore, is prolly quite lean considering that it has a race exhaust on it.
I shone a torch down the ports and couldn't see much of the valves, it did look as if there was some carbon on the back of the valves, but I should be able to get hold of a borescope this w/e for a better look.
Does anyone have any pictures of exhaust valves that have been running too lean so that I can make a comparison

[Neosophist]

115 / 118 is later Jap spec.

Even with a full system this very unlikely to be dangerously lean unless you have some weird modified airbox / intake system or you have other faults with your carbs.

Black-smoke is usually excessive fuelling...

[scooble]

airbox is standard, I was thinking of going for 120/122 or do you think that's too lean too?

[arsey30]

If one ex is orange then it was running weak, no need to check.

Could be air leak, or the pilot jet or circuit may be blocked, although it only operates up to 1/8 throttle nominal, it does still controls fuelling up to about 1/4 throttle with a diminishing effect.

If it runs hot at rest by blipping, I doubt that main jets are to blame [Covers 3/4 to full throttle], especially as it is only 1 cylinder

Dave.

[Neosophist]

Only just re-read this.

I edited my original post.. i mean the jets are unlikely to be dangerously lean.

I just noticed that your pipe is glowing orange too.. as Dave has said.. this indicated a lean mix...

check the pilot screws / passageways and floatheights

[scooble]

I've checked float heights on other carbs before, but where do I measure from on the NC carbs, and what should the heights be?

I took the carbs off and gave them a thorough clean and blew all orifices through with an airline. All air screws have been turned out to two and a quarter turns.