Woodgased BCS walkbehind

Jaka, I think a piston bolt would be a good substitute for a drill


I was researching it last night. the most common thing I could find with the highest carbon content was either wrist pis like tone suggested or torsion bars I think they were 0.60% carbon. which is right on the line of mild carbon and high carbon. I like the idea of wrist pins because I can probably find them with holes already in them

How specific in size do the holes have to be?


Jakob, I know for a fact that General Motors wrist pins are hollow, and I’ve come across two sizes when I worked at the dealership: 12mm bore and 14mm bore. Maybe find a dealership and ask if you could buy some scrap from them. Far fetched but they might work with you.


Jakob, the drill bit has a 6 mm hole, is this the right size, but it depends on the construction of the hot zone itself,… I know that the piston bolts have holes of larger diameters, but it is not a problem to reduce it, you heat it to white and reduce it by forging to the desired size, I did this with my first gasifier


How do you mix the water into your charcoal? how do you measure it?
Also what size charcoal are you using?


Hi Jake.

Just pour over the charcoal realy… to say the truth l do it by feel usualy but l guess it lands to about 20% water.

I use the usual engine grade size.

Edit; usualy my engine grade is everything smaller thain 3/4" minus dust


It seems the ideal water content is about at the point where the dust stops forming when handling the fuel. But every sistem is different, my Škoda liked much dryer fuel per instance… increased cr might has something to do with it…


hello jakob, it depends how the gasifier is constructed…updraft needs dry coal and eventually water drops or steam adding through the nozzle, because with moist coal the water is not ctacked but escapes with the gas…
downdraft can have moist coal, but here depends if the hearth let bypass the water vapour or not…kristijan has, when i remember right, a woodgas hearth in his skoda gasifier, where no water vapour can bypass, so all transform to hydrogen, but the metall is exposed to more heat…
in my downdraft gasifiers i have a wider hearth with some charcoal around to protect the metall, but there vapours can bypass…so my coal should not to be too umid, otherwise i have starting problems …when my coal is too umid i must ventilate with open hopper for 10 minutes to dry out, than starts well…
a bit umidity in the gas though can be useful for filtering, dust remains easier on the filters…
my modest insight…please correct if it is wrong
ciao giorgio


Giorgio I think you hit the nail on the head. Like many things involving gasifiers the answer can be “It depends”.


With warm weather, it was time to put some grass on the ground. Tone shaved a few mm off of this engines flat head for me and l polished the valves this winter. I was real curious of how this will effect performance.

Well. Let me say guys… whenever you plan on gasifying an old, low compression engine like this, l strongly advise you go the extra mile and do those things. Yesterday was the most pleasurable mowing experiance l ever had, on any BCS mower. Never have l had an engine run so smooth. They fart and hickup a lot on petrol, the carb is primitive, the governor is fast so they always act funny on petrol. But with woodgas and the better compression l got now, thats a different story.

I was most surpriced by the throtle responce. No hesitation even after a long idle.

Also, l have noticed that while mowing, before the cr increase the governor held the throtle preety much 100% open. Now it holds it at half open. Means the engine is way more efficient, and indeed, l was mowing for about 45min yet l still had fuel left in the tiny 2.5 gal hopper


Sorry for bad quality. Neighbours camera


hello kristijan, you have reported more up on this thread that your mower was not more to start last year, also not more with gasoline…
was there another problem or only the valves?
my little mower, the blue bertolini, this morning was absolutely not to start…cylinder head off- the valves seems to close correct, spark plug gives spark…
two days ago we have had a heavy hail, all the gras lays very flat, difficult to cut this year…


Kristijan, do you use slope boots in your area? It looks like you could benefit from slanted heels :smile:
The story behind the “slope boots brothers” goes back about 100 years in a nearby village. The bachelor brothers were not extreemly poor, but pretty cautious about expences. Their boots were worn, with extreemly slanted heels and according to the legend their excuse to always wearing those boots was their farm was situated in steep terrain :smile:


Giorgio, the fact it didnt run well on petrol could be due to the clasical problem with runing woodgas trugh a carb, dust in the orfaces. But the motor ran fine on woodgas then suddenly, bang, boom and the engine dyed. It was found later that the culprit was a crack in the gasifier leaking air in and at some time the gas egnited, bang… Runs smooth now.

JO, we too joke here that our cows have shorter legs on one side for the same reason :smile:


yesterday we polished the valves also. the exhaust valve seat was not fine more, thoug the valve sets strong on his seat…now is to feel better compression, will try starting after when not rains…
here rains in the hay every day a bit, so not dries, hope you have better weather …
i remember you have had problems with pulsation in the filter on your mower, so filter cake cannot build up on the towel…have you found a solution?
ciao giorgio


Oh mess… quality of hay goes down…

I have not. I tryed foam but the gas is too hot for it. I think l will soak towels in oil and try making the filter out of that. Shuld stick on it better.


I changed the oil the other day, what a mess! All gooey from carbon dust. Never had this happen. The slow turning single cilinder engine pulsates too much on the filter…

So l soaked the towel with a mix of engine oil and gasoline (to thin the oil) and wraped 3 layrs of it. Its a bit more restrictive but still has enaugh power. After about 2 work hours the oil seems to be the same colour as it was so it seems this worked.


gohin poulenc has had a safety mesh at the end of the filtering-cooling path, also with a bit of oil on it…i think easier to clean as a towel…-ash water…
i use as end filter the water irrigation filter…it is 4 to 5 times finer as gohin poulenc´s mesh…
i have never tried with oil on it, but will try the next time when we make again some washed hay…
on your towel filter you could make a tighter net inside and outside, this could also help minimize pulsation…?
my dust trap over the cyclon has drastically reduced the dust in the filter train…


The safety filter on the Gohin wasnt ment to filter anything, it was ment to fill and tighten up (kill the engine) if the sack in the main filter burst.

Its important to know the principle of sack filters. The cloth or mesh isnt whats doing the filtering, the so called “cake” is. Sack is just there to hold the cake. A layr of packed dust on the surface is the actual filter. Problem is, with such strong pulsation as on the single cilinder engine, this cake can not form.


i think the gohin filter has booth funktions, because the driver has always a second clean filter by hand to replace regularly…so is described…