/6 cylinder temp

[mneblett]

you increase the mixture at idle to get max exhaust gas temperature and then went back "one notch" lean.

go rich to get max power, not max exhaust temp. Once airborne, lean out at cruise for economy/range.

As a rule, leaner = hotter.

 

[mneblett]

when i had the one side running rich, i'd pulled off the exhaust pipes and valve covers as part of deep winter maintenance. the hot, rich side exhaust was sooty black, the cooler lean side tan inside the exhaust. additionally, the hot rich side was so much hotter it had scorched oil brown staining under the valve train whereas the lean side was perfectly clean. this all surprised me too.

Actually, you're reading the signs backwards. The black sooty coating is from incomplete combustion (i.e., too much fuel for the available oxygen) = lower temp combustion. The brown staining, to the extent is has any temp component, is due to the head *not* getting hot enough to release the oil byproducts. Sorta like (well, not much, but you'll get the idea) a self-cleaning oven -- dirty from 350F cooking, clean after 500F+ self-cleaning.

Here's a link to an article with a chart from Lycoming: http://www.n66ap.alexap.com/Mixture_article.htm

You'll see that exhaust gas temp and cylinder head temp climb as you go from rich to lean, until you are so lean that you are no longer burning much fuel (or making much power).

 

[DanHoug]

i'm not reading my CHT gauge backwards. right side showed high gauge temp with a sooty exhaust, and burned oil on the head. it wasn't brown deposits from a sludgy cold engine, it was a scorch like on the bottom of a baking sheet. i fixed the rich condition and gauge temp returned to normal.

 

[lkchris]

With aftermarket products, (say made in China) is it possible the quality of plating may vary enough to cause the difference in bluing at the same temp.

It's never been clear to me, either, that the radius of the bends in the two headers is the same.

Heat in cylinders is a pertinent topic with Airheads and the introduction of Nikasil cylinders for 1981 made a massive difference.

On my '84 R100RS is was essentially unnecessary to ever pull the dipstick to check motor oil level, as there was never any change. Couldn't say this about iron-lined cylinder bikes.

Instead of putting so much heat into the engine oil, the Nikasil cylinders very efficiently moved it to ambient, cooking the rider in the process.

They say there never could have been an R80G/S without Nikasil cylinders.

 

[8ninety8]

Talking about two different things. Cylinder head temps and header temps, two different things. Gotta read plugs for cylinder head temps. As for pipe temps, I look at where the blue is to see where the unburned gas is being burned off. Maybe nearer up or further back, doesn't matter to me. May be wrong, but, the bluing is always down the line from the exhaust nut, meaning, well, I let others explain it. FWIW, I'm no guru.

I am getting a couple 150 mains however, just for fun.