Originally Posted By: asand1
Pull the spark plug and see iff it still has as much "compression". I bet there is carbon on the head above a valve,
causing more resistance when the valve opens.
With no plug in, of course it doesn't, spins free (and makes a funny gasping 'wwahwahwah' noise). Is it possible for carbon to buildup enough to impede a valve, in the time fame of three strokes..before the valve again travels it's entire path.. does that happen? Aside from all of that, though.. cylinder pressure leakdown decreases with head carbon buildup?
Originally Posted By: spasm3
You have been running a gas engine on a ?70% diesel blend?
you probably have a bunch of carbon all over the piston top.
Nahhhh! lol I promise, it's not carbon
That diesel run was a short-term experiment, and as I noted earlier, it did burn very cleanly in a HCSI mode, as noted by the same usual non-odourous exhaust, lack of smoke or soot on the muffler and clean plug; areas that would be notably sooty with poor quality combustion. Only time I could get it to blow a little diesel smoke was when disengaging the run handle just enough to cut the spark, but not enough to hit the brake, if you know what I mean! Mmm smelled like truckin'. Otherwise, no smoke faint smell, proper combustion.
I appreciate the ideas, but I'm not seeking diagnosis. There is nothing wrong with the engine, it runs incredibly. Exhaust smells very 'clean' as far as uncatalysed small engine exhaust goes, it has excellent stall resistance, esp with that diesel mix because it would compression ignite under those loads! Nevertheless, it runs regular gas 98% of the time, and has never knocked.
The engine's had a [excessively] good start to it's service life with about 10 initial oil changes in about 10hours, broke in hard, has been filled with a variety of oils from Esso XD-3 0w40 to the old Castrol Motorcycle mineral SAE50 in there now. Doesn't burn oil. It used to have a piece of dental floss tied to the throttle that I'd yank as a preemptive 'booster' for heavy mulch ops over wet bulky grass, a highly engineered setup
It's been kerosene flushed and drained at all angles to wash the break in sparklies away. Aside from being covered in winter salt dust, that engine's service plan has been BITOG neurosis tier
Anyway, this isn't normally a kind of post I'd make, but had just felt so compelled yesterday when what had happened made me chuckle and want to share.