Glowing exhausts

Ignition timing

It's not a gamble.

Set the ignition correctly, then follow the carburettor tuning procedure.

Some pattern exhaust pipes are made of such thin tubing they will quickly go red hot when the engine is run hard..  Any Chroming will then turn blue.  Then they start to rust. 
Below are my cheapo replacement pipes after just 20 miles.The previous standard Armours set had covered 10,000 miles and were in perfect condition but I wanted some swept backs. 
The Ignition Timing and Carb settings were not changed.

On a 1930 Ford model A with distributor fitted wrong way. Ignition timing my bet.

Just the once when the ignition timing slipped. Blued exhausts are different - often an indication that the bike is being used to its full potential.

Flame front is running down the pipe because ignition was too late...
J

This is what happens when the exhaust valve sticks open on a 16H...Yes, it was glowing red there when I stopped.