Here is a video. Most just add a tee.
Later I made another mod to lean it a bit when at idle.
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Wow, ask and ye shall receive! That’s a sweet video! So if I’m committed to not running gasoline, that’s a nice way to use the existing carb as the inlet tee for the chargas and air. Downside is that you have to get the number/size of holes correct so that the throttle will still work and the idle and all that works correctly.
If I tee the air and chargas before the air inlet to the carb, the carb and throttle “should” work right out of the gate. And I could run gasoline if I make a mess of the whole thing. I think…?
If I’m understanding that correctly, I think it seems like the safe thing is to tee it before the carb and get the tractor running. Then when I have more confidence, start modifying the carb (or get a spare to mess with).
Thanks again for the video, that was awesome!
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Go for the tee first. Most of the time it is best to start simple. Do not spend a ton of time on your first charcoal rig. Get your fingers dirty first and then make improvements. Your mileage will very, so to speak, from everybody else. Now, if you were building from plans I would stick to them for the first go around. With charcoal you do not need a set of perfect plans.
The mixture valve will still need some experience adjusting even with the tee method.
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Thanks Jeff, good to know! First step, garden tractor. Second step, charcoal retort heated greenhouse. Third step, charcoal truck. Fourth step, wood gas power generation for the property. Fifth step, fix all the world’s problems. 
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Very good video Jeff . Thanks for posting .
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Hi Mike, Sorry about the delay. That is how I did it. You can go behind the carburetor with the chargas inlet. If I had to do it again I think I would go that route. The only reason I did not do that on my first was because then you have to build a throttle system. Jakob
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Thanks Billy! I’m slowly learning how all this stuff works. It’s probably very obvious that I haven’t tinkered with engines much. This will be a great opportunity to really dig into this tractor.
So if I use the existing carb, I get to reuse the throttle and have the possibility of running on gasoline. But, per Jeff’s awesome video, there are restrictions in the carb that could be improved upon if I only want to run on chargas.
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take some pictures of the carb assembly with something for scale. A lot of those older small engine carbs were built big so it gives you some leeway. The modern ones are sleek and tiny forcing you to modify.
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Will do David! My goal is to give the tractor a thorough rebuilding/fixing/cleaning this summer. If I’m really ambitious I’ll jump into this project as well. I do need it running for winter snowblowing and fall/spring firewood hauling. So I should have pics of the carb by July. It is a 44 year old tractor so hopefully the carb is huge 
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Your first go at it will not be perfect. Start simple, start faster and start running that engine. Fine tune later and endlessly… It never ends…
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It never ends? Well poop…
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That’s the good part. When you stop learning you have to admit you’re getting old.
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I would say you are effectively dead when you are not willing to learn.
Rindert
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