I have a 1981 Yamaha XS650. I recently put in K&N stock replacement filter (ie, they are in the airbox and conform to the size of the original), however they may be leading to a leaner mixture because they purportedly let through more air. I want to tune my carbs (yes, I know that the B34s are n...

To understand the question at large, it is first good to know what the application is and how it came about. The engine in question is the older type of 4-cylinder engine used in Series-A Minis (not the modern BMW manufactured one, but the one produced by the British Motor Corporation). This Min...

No worries Paul. I think my response has caused a little jealously. Technically it's fine though. That said, I'm happy to hear - with proof - how it's wrong. I like diesel engines, but their efficiency benefits when compared to typical gasoline engines are not what they used to be; for the r...

I learned recently that many older and some newer diesels don't have throttle plates to control airflow. I was also quite shocked to learn about a condition called diesel engine runaway. Apparently a diesel engine can run out of control from diesel and oil pooling in the manifold. It seems tha...

Since the diesel has no physical throttle, power is controlled by limiting fuel. Air is always available so any unintended, un-metered fuel will cause the engine to increase rpm and power output. The most common sources are blowby oil and oil leaking from a worn turbocharger, these then pool in t...

I keep hearing about DEF ... what is it and why is it used in conjunction with diesel engines? I know it is a more recent thing (last decade), but don't know much about it.

Torque is the name of the game. High torque is needed to move heavy loads. If comparing a gasoline engine to a comparable diesel engine the diesel will always have higher torque. The higher torque comes from the need for a higher compressing ratio needed for compression ignition. To achieve the h...

The goal was to prevent valve float at higher rpms. Given the metallurgy of the day it required a lot of spring pressure to ensure that the spring was push the valve closed. The desmo unit mechanically forces the valve closed as opposed to using spring pressure. This would allow an engine to ru...

Almost every motorcycle I have seen has its air intake mounted such that it is sucking in air from the direction opposing travel. According to fluid dynamics, if the intake is made to face forwards, the engine would benefit from ram-air effect, which can result in higher engine power output. No...