I have only cleaned my burner down to the grate 3 times in 6500 miles and found several marble sized gray hard clinkers in the 6 1/2” restriction
Is that the name because of the sound when they hit the pan?
The only reason to clean to the grate was to check for erosion (none) and once to increase the restriction from 6 1/2” to 7” to feed my 460 CI Ford.
Hi Mike,
Are you running charcoal?
No
It is a Wayne Keith design wood burner
Meaning it makes charcoal in top half and burns it in bottom half
Hi Michael, I think @Wayne has a 7 1/4" opening on his V-10, your engine is pretty close to his in CI. I have a 7" with my 318CI engine. You might get a little performance by going a little bigger. But watch out for tar production at lower speeds.
Did you get the exhaust preheat air going on your truck?
I have always wonder about preheated air vs. non preheated air in gasifier and the formation of clunkers. In mine just some hard ash at times.
Bob
Hello Bob and Michael.
I would need to go back through the building thread of my V-10 to be sure but I think I have had a 9 inch choke for about three years now .
Truck is running good , Almost 31,000 miles on it now . 
Yes i have a exhaust preheat. I built a shroud around the catalytic portion with 2 of the 3”blowers and a check valve upstream.
I only use the blowers for startup
My burner will overheat if i pull more than 5” of h2o for more than a few minutes
This limits me to 45 -50 MPH on a level road
I used 3” thinwall tubing everywhere except 5” at the exit rom the burner
I went back and looked. It is 9 1/4" on the tape measure on the new build. That’s a big reduction hole. Wow!
Bob
Sounds like a bigger choke may be in order?
What temp do you consider overheating, and where are you measuring it?
488 cubic inches… 
There is a thermocouple at the entrance to the cooling rack, probably 2’ from the burner exit
The temp runs in the 500 to 600 range when the 460 CI engine is under 2000 RPM.
On a gear down to climb a hill RPMs up to 2500 and vacuum at 15 to 20” the temp will rise to 650 and then rapidly climb to over 700! WHOA
Time to go hybrid and back vacuum to under 5”
Good morning Mr. Mike
At about 650 is when I also will go hybrid.
The last couple thousand miles I have only noticed one clinker about the size of my thumb last week.
I am about to fire up for the day and hook to a trailer .
BBB
Hi Michael, I think the highest temperature I have seen coming out of the drop box on mine has been at 500 * f and that was at cruising speed of 70mph. About 300 * f at the rails between the third and bottom rail down from the top. My top gauge is in (BOO) mode, Bad Operating Order mode, need to replace it.
Bob
I didn’t mention that at about 650 to 700 deg F the power rapidly drops off and temp can go to 900 in seconds.
What this means is that I am pulling so hard that some O2s are getting through and burning up my woodgas