The Motofier - a Simple-Fire powered Honda XR-100R

I’ve been working on this project for some time, but today we had a very successful test. This is a 2003 Honda XR-100R dirt bike, obviously in very good condition for its age. I already had this machine, or I would have chosen something larger, perhaps with multiple cylinders. The gasifier is perhaps a bit large for the bike, but I wanted something with some range compared to that fire-extinguisher-equipped Honda from the 80’s which we’ve all seen (previously the cover photo for the Yahoo Woodgas group).

Anyway, the Motofier is powered by a Simple-Fire style, updraft charcoal gasifier, complete with exhaust gas re-injection. The mesquite charcoal was made by Ray Menke in an Gilmore style open retort which he and I built (actually he’s burned out a couple by now). The charcoal was ground to spec in a grinder which I constructed. The holddowns on the pot were pioneered by John Rubins of our charcoalgasifer group, and I constructed homemade valves for the exhaust re-injection and air intake using an idea from George Adams, also of our group. However, I used elliptical valve plates rather than round ones, and JB Welded them in place rather than bending the plates. As everyone knows, “hooking it up” takes the most time, ie getting the plumbing done. I used a combination of everything for that - including the kitchen sink … drain pipe, that is. There’s also a modified ice maker valve on the filter as a drain! The gasifier appears to be “just sitting” on the rack, but it is held down securely in a novel fashion. The stainless bands for the filter mounts were hand Sawzalled from some 18 or so gauge stainless from a copy machine part. It was too thick to cut with snips. Did eat up a bunch of Sawzall blades. Then when I went to drill the bolt holes on one of the nice, hard won stainless strips it was snagged by the drill bit and wrapped itself around the drill press chuck before I could throw the switch. Fortunately it hammered out nicely. DJ must have been watching over me, because I’m not sure how these mounts came out so nice.

Anyway, ran it about 30 minutes today and it appears to have over 50% power, maybe more, even without touching the ignition advance (which would be difficult on this machine). Made it up the “big hill” on our street in first gear - 3rd would be normal, I guess. Idles nice. In operation the air valve is totally shut, and it seals fairly well. Woodgas full open, of course. Exhaust gas valve full open, but need to add some backpressure to force more to the gasifier intake. Temp at the top of the gasifer came up to almost 300 F, due to the void space, but the gas was cooled to near ambient before it went to the filter. The gasifier exterior was ambient at the base and increased towards the top to something over 140F. Will check to see how much charcoal was used when it cools down.

Video, here:

Martin Payne


Howdy Martin,
Really nice install!
I’ve been wanting see this type of conversion… I have an old Honda 4 wheeler, it’s only a 250 but it sure would be lots of fun.
How about some details on how ya hooked it up and such, some stills would be good for the low bandwidth guys :slight_smile:
Again, Nice Work Thanks for posting!
HCWT (Have Charcoal will Travel)

MP, i watched and again and again…
super job, well done

TerryL, there are 8 photos here: These were posted on July 15, which seems like a long time ago. I bet Martin has some more photo details to add by now. In fact, now that he has “driven on gas”, he might even consider a blog page on DOW. Ray Menke

Good Morning Martin P,

Really super job!! Thanks for posting.


sweet ride!

Nice looking setup…

Martin, I’m glad you are still at it. I can’t view the video. Please post a few pictures when you have time so I can see what you built. Thanks, Mike
PS, just getting ready for winter here. I am having major trouble walking so will be staying put here this fall. It sucks … One day I could run and ride a bike and the next day I couldn’t pick my feet up off the floor. I have to head out into the field … Strong winds today. Hope I don’t get blown over … Gerber is still doing well. I have to wash the hinge out with hot water from time to time as food products wind up in it :o) …

Thank you all for the kind words and support! It took longer than it should have, but it is nice to see it run, and run well. Had to get it finished up before I start on … a truck, finally! 1995 F-150 short bed, regular cab, 300-6, 5 speed. I wasn’t ready for it, but a friend had it, and it has been “lightly used”. I couldn’t let it get away. He did much work to it - new radiator, helper springs, etc. I know more HP would be better, but I love straight sixes and the Ford engineers had their way with this engine before they were forced to give it up - MPFI and “luxuriously long runner intake torque making” as Mr. Unruh more eloquently says. I wanted a Supercab, longbed, but after talking with Carl in Arkansas I’m thinking maybe the weight savings will be beneficial. Also after seeing Richard’s truck in Arkansas I think I will lose the bed, build a flatbed.

Sorry, back to the topic at hand! Will post pics, happy to answer questions, help anyone - as many have helped me. I stumbled onto the PVC under sink drain pipe for the intake - really handy stuff - easy cut and fit with the compression fittings, etc. Most of the other PVC fittings are not glued, just forced together. Lotta time at Home Depot with stuff laid out on the floor and the plumbing guy asking me, “Well, what are you trying to do, what does this go on?”

Also going to post on charcoalgasifers the ellipse making lessons I learned, can do so here as well. Basically a ratio I backed into for converting a pipe ID to the appropriate compass drawing radius for the ellipse approximation drawing shortcut. Sorry, I know the WK uses round valve disk “dampers” just fine, it’s that little German in me that I just can’t seem to get rid of …

Ray - didn’t know there were blogs here, will have to look.

Congratulations, Martin, you did it. And in grand style to boot!

Thanks Carl! Really enjoyed meeting you and Richard in AR. Was sorry the time was so short, and I forgot to even ask for a ride in the trucks!

I notice the charcoal gas line passes right behind where you sit. A real “seat of the pants” temperature gauge!

AWESOME! those hondas last forever… the only suggestion i have is to route the lines where a tree on a tight trail wont snag them. how about a video with those pics?

edit, saw the video above, very nice

Ha! Ha! OK I heard my name spoken clear up here.
Thanks for the stills photos MartinP.
Great system set up you built here. Ties in with something I said in a recent personal corosopndence, and have consistently said here on DOW site - for the small light mobile systems the proven way IS CHARCOAL GASIFICATION.

No offence intended to any; but the raw wood fueled, very complex, and overweight then, motorcycles and even many mini-car raw wood fuel systems end up being “ship in a bottle” pretty impractical to use out in the real bathtub of Life.

Steve Unruh

Hi Martin
Thanks for posting. Very nicely made, looks store bought.
I Eco a few of the other guys, post a few photos.

what a great little system… These days I’m thinking about an old atv for conversion. I like how everything came together so neatly…
Congrats, David Baillie

Martin, Great job !
I’ve been contemplating doing up a bike but time is tight and the Dakota gets the attention first.
I’ve always admired those Yamaha TW200 racks, great to see one put to good use!
Thanks for posting the vid and pics… inspiring!
Tim J


Amen to that! Not to mention the plastic seat, as Ray pointed out. I had planned on it being cool by then, and so far that has been the case.


Ha! Ha! back atcha, and thanks. I tend to agree, but then there is the work of DJ on woodgas tinyfiers. Or Terry’s GEK riding lawnmower, which seems to work real well. (However I heard the engine blew, or something, need to track him down, find out about it.)

1 Like

Thanks for that! Yes, in Mexico they can rebuild an old Honda 70 forever. As to the lines, I was concerned about how I did it, but in the end this is really not a brush or trail buster, and I shun 90’s (elbows) for low pressure flow. So, I just accepted that it would hang out a little, and made most of the “hang” out the back. Will try not to pop wheelies. Having said that, doing a better job of keeping the lines tighter to the gasifier would be a worthy goal.