Finally got the air cleaner adapter for the 420cc Predator that is used for the 9000w generator from Harbor Freight. It adds an air horn that allows you to hose clamp on a pod filter, which will let me hook up an air mixer to the engine. Very gentle taper down to the carb bore size.
This is going to be started once I have the engine fully broken in and once I have the Sierra finished. I will take my time with this build because I want to do it right the first time. I’ve mentioned it before but I’m thinking of building a Svedlund style single nozzle downdraft charcoal gasifier with a cast refractory hearth. Charcoal because the gas is easier to clean and the hearth is merely an insurance policy against tars, and will maybe let me mix in a little wood.
Body of the Gasifier is my 100lb propane tank, nothing fancy and has sturdy walls. I don’t intend for the hopper to be very huge, if I can get an operational day’s worth out of a hopper(12 hours) then it would exceed my expectations. Conservatively I think it would be more like 6 hours runtime.
I have two silicon carbide pieces I plan to use for the nozzle tip, one is a spare. 25mm ID and just barely doesn’t fit in a 1.25" sch40 pipe but should fit with some filing or sanding drum on a Dremel. Pressed fit with some silicate based muffler sealant as a glue to help it from falling back out due to heat cycles or vibrations.
I’m planning to mount the entire unit on its own wheeled buggy, separate from the generator but just as mobile hopefully. I can most likely recycle my ammo box filter for this build, worked great with a 2 liter engine should be no problems with a 420cc engine.
By the way, I will be adding a nipple to the air mixer so the valve cover breather still gets sucked into the engine. I don’t want to mess with any of the designed system, a lot of minibike guys just use an air filter but I feel like that hurts more than helps and they just want a quick solution. Any vacuum lines running to the current box will be rerouted to the air mixer assembly. Main goal is to still be able to seamlessly go from gasoline to producer gas via the fuel tank petcock and some adjustment of the mixer. The occasional use of gasoline will help clean the valves of soots if any get through.
I keep going between the idea of using cast refractory with added porcelain and wire aggregate, or ceramic wool and stiffener with a light refractory lining pasted over that.
I have both at hand so it’s not a matter of cost, just trying to think which would last the longest or be the easiest to maintain. The refractory that I have is Rutland Dry Mix 211 Refractory Mortar 2550°F. I’m not even sure if it would make a good cast hearth but it’s what I can get.
I just stuff a piece off of those green scrubby pads in the hose. No need to complicate its just a crank case vent to keep presure from blowing all the seals out. Keep the weight off those bolts Ive broke quite of a few and those bolts generally snap off flush with the block. And how they manage to cram a full bottle of green lock tight into those small holes is beyond me.
Yeah I was planning to make a brace for the PVC pipe that will plumb into it clamped to the frame of the generator. Either that or high temp hose. Mixer will definitely be not near the carburetor to keep the majority of the weight off of it. Going to make the air adjusting valve myself, I’m thinking a spring loaded butterfly with a thumbscrew for a hard setting once it’s dialed in, I figure engine vibration would otherwise rattle it out of adjustment.
