A valid point, Jim.
After each engine run on woodgas, I switch back to gasoline for at least
10 minutes. I am hoping this will keep things clean enough for now.
I have lots to do in the next few months to get ready to go at again in
the spring.
One of the main projects is to make a final filter out of a nice 5 or 6
gallon steel barrel that has a clamp-on lid. It'll be filled with wood
shavings and mounted in the cool end of the gas stream, just before the
engine.
But the MAIN project is the reduce the diameter of the grate area in the
gasifier so I can get the "below grate" gas temperature up from the current
max of about 600°F to at least 1000°F. That will get rid of almost all the
tar.
To support these and other changes, I will rebuild my Arduino-based
datalogger, adding more pressure sensors so I can directly monitor pressure
drop across the new filter and a few other things. I will also add some
"traffic lights" to tell me, at a glance, if I am in the "sweet spots" for
grate temp and suction.
I may even start to make the datalogger into an actual process controller
by adding a servo to adjust the fuel gas mixture.

Pete Stanaitis
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"Jim Wilkins" wrote in message
...

One of my books on alternate energy warns that the first sign of trouble
will likely be the intake valve stem stuck in its guide after the engine
cools. IIRC if you miss that the second is either a bent pushrod or the
valve smacking into the piston.