All modern engines are fuel injected, so the intake valve only ever sees filtered air.
So, no matter what type of fuel you use, the intake valve should never get carbon deposits.
Therefore I doubt these results... I suspect they are either doctored, or they use a very old carburettor engine which is probably deliberately mis-adjusted to make lots of carbon for the photo.
After all, that much carbon in just 100 hours of running would lead to a total blockage in just 300 hours. And my valves don't get blocked every 300 hours if running!
All modern engines are fuel injected, so the intake valve only ever sees filtered air.
So, no matter what type of fuel you use, the intake valve should never get carbon deposits.
Therefore I doubt these results... I suspect they are either doctored, or they use a very old carburettor engine which is probably deliberately mis-adjusted to make lots of carbon for the photo.
After all, that much carbon in just 100 hours of running would lead to a total blockage in just 300 hours. And my valves don't get blocked every 300 hours if running!