Originally Posted by combatpigg

It depends on your starting and tuning habits with diesel fuel. Don't let anyone tell you that running them this way is more forgiving..!
You have to run diesel engines very close to hydraulic lock ...more than with glow fuel.
This isn't conducive to a long and happy life with lightweight internal engine parts.
The fuel residue will creep under iron on covering and age a model prematurely, your clothes will stink, women will shun you.
I HAVE seen AME .061s on diesel turn 7 x 3 APC props 13,500 on a twin engine model. The guy who owned this set-up was a huge diesel conversion fan and he had lots of experience with them. He always backed off the compression screw, way off before using his electric starter. He was too old and stiff for hand flipping. With a twin engine model, hand flipping means a lot of time wasted when you could be flying.
Any way, he would crank the engine with the compression set too low to fire. As soon as he saw fuel reach the spray bar he clamped off the line. He would resume turning the engine over as he raised the compression enough to get it to "bump". Then he released the clamp on the fuel line and usually all conditions were just right for a safe start. To be sure the engine isn't over compressed the exhaust residue should ideally be brown but not black. Under compression causes the engine to misfire similar to being too rich. Over compression will cause the engine to heat up too much and lose power. Many times this condition will "creep up" during the run, especially if you are working the model really hard with constant maneuvering [like in a combat match].
I keep a couple of the 1/2 A RJL brand diesel heads handy and mix small batches of 1/3 lamp oil, 1/3 John Deere starter fluid and 1/3 castor oil for occasional runs.
Ideally, the Diesel Gurus say to use glow engines that are already broke in on glow fuel and are in tip top condition before switching to diesel. Well, ideally I wouldn't mess with any conversions and I'd just buy one of the PAW engines..!
1/2 A glow engines just aren't built heavy enough to give care free service on diesel over the long haul.
If you tear apart a purpose built diesel like the PAW, you will see the difference in design strength.