Starting from scratch and looking for input: KLR 650 build

I’ve just recently joined the forum and i’m starting a new producer gas build: a 1988 KLR 650. (although first i’m rebuilding the top end of the engine…) From what i’ve read so far a lot of members are recommending going with charcoal to simplify the onboard processing. I see the logic although i’d rather do straight wood for romantic reasons…

Can folks supply any knowledge/links to parallel projects? Any direction/food for though would be appreciated as i start designing.



sounds as a nice project for “excercising woodgas” , dough the only “small” bottle neck is going to be the pulsating gas stream / restriction from filters and cyclone…

whatever you build, take in account to build with the least restriction possible or just start with a charcoal gasifier to get the engine feeling and on the simultaneous track the wood gasifier.

Make sure to have your battery always fully charged … and welcome in the land of driving with lemons…

Many good folks around here and many experienced advice available on DOW…

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Here is a link to a parallel project using a small Honda running on charcoal. The Motofier - a Simple-Fire powered Honda XR-100R

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has anybody ever added a fan or a gas storage vessel to try to even out the pulse for a single cylinder? without any experience i don’t know how much of an impediment a single cylinder is in the grand scheme…but its what i’ve got so i’ll be working with it!
any advice on the best technical resource for starting to size the components? using calcs on the site a roughed out my gas requirements at around 7-8 l/s

Peter Janes,
Gary Gilmore has a video of his Harbor Freight 8750 watt peak (7000 watt) predator running on charcoal. I suggest you copy his system but pay careful attention to gas flow with sweeping bends and no restrictions. This engine is a horizontal single cylinder 420cc OHV engine. In the video, Gary points out his 16 gallon barrel filled with charcoal, and at the gas outlet, he shows a cooling disk. This cools the gas slightly, but also prevents sucking pieces of charcoal into the cyclone. The screw-on lids for 5 gallon buckets are available from Amazon. Sump pump hose is available from for a reasonable price.
There used to be sub-frames available for the KLR650 to convert it to a sidecar rig. One idea would be to weld up a frame to hold the charcoal gasifier and a 12 volt battery, forgetting the tub for a passenger.
If you do use a simple charcoal gasifier, then it will be necessary to master the art of making quality charcoal without creating smoke. A larger TLUD cooking stove can create a gallon or more of charcoal each time you use it. (One thing leads to another, and it is very easy to get distracted, at least it is for me.)
Peak torque of the KLR is around 4900 rpm, and I don’t know if it will even go that high on woodgas without some sort of adjustable timing advance. On woodgas or charcoal don’t expect more than 15 or 18 hp, and if you go with a sub-frame to hold the gasifier, it is going to be heavier than with a solo passenger, and is not going to have much performance, but it will be very unique.
Where are you located? What sort of riding conditions do you have where you live? Any other goals in mind for the bike?

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Yes. I have tried/done both reservoir/tank storage; and fan/pressurized boosting for larger single cylinder engines. Woodgas live from a producer.
Works, kinnda’ sorta’ with problems of BIG kaboom in the reservoir system under variable engine loading/off-loading conditions.
And a booster blower really needs a rather complex sensing feedback and fast reactive variable boosting capability to again respond well to variable engine loading/off-loading conditions.

All in all just much better to use the single cylinder engine ability to pulsate back and sweep clean the gasifier grate/hearth of exposed charcoal fuel ash.
Your reading here of others motorcycle? conversions and historical conversions will prove this to be pulsation sweeping of the the hearth and filtering areas to be important on system to be kept small, light and mobile.

Regards and welcome to the DOW
tree-farmer Steve unruh

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thanks for the food for thought! I’m on a small island in BC, canada. (its pretty flat and quiet around here). for me its a learning process. i don’t have high expectations of uber-performance. (i still have a stock gasoline bike for going fast!). i was hoping to avoid a side car and try to mount most of the gear as possible on low rear pannier racks.
Has gary gilmore posted any of his technical specs?

steve, you’re saying that the pulse of the single-cylinder actually has a useful function? i suppose the next step is to start sizing components…


Hi Peter,

Yes, the pulsing “can be” used useful… if/for… but…
Its quite difficult to explain what it does or don’t do, but once you can imagine yourself the picture its easy to use / avoid

ok, i give it a try to explain:
your car consumes more fuel when it have to accelerate and stop frequently, compared with a steady speed.

imagine the flow of the gas… its only sucked in YOUR engine during the intake stroke… = 25% of the time on intake.
Now, that gasflow have to start at the beginning of that 25 % and slows down before the end of that 25%

Next is to imagine the inertia of that gasflow…
each time the intake valve closes, the gas continues its flow, bumps on its own pressure and bumps back to the gasifier…

Old 2 strokes do use a kind of solution to prevent the bump back, but use the inertia to fill a “flask” with that building pressure, releasing just in time when the 2 stroke “asks” again for the next filling…

If and if… the design of your gas mix intake , hose lenght, hose flexibility is well tuned… there is a huge amount of that puls energy used to “extra” fill your cylinder… hence more power available.

special for low rpm.

So, to recap, a multi cylinder engine gasifier has a steady stream of gas, a one cylinder engine will only take/have 1 quarter off the time to produce the amount of gas needed.


missed to reply on this one…

as myself, using the basics of a Gilmore gasifier, i can advise you to some extend if you want to build a charcoal gasifier.

Your gas flow need will only be 5 to 6 liters per second, 3000 rpm @ WOT
This due to the filling grade of your single cylinder.

If you design for that flow, nozzle speed 25 m/s at 3000 RPM, then you’l have a reasonable idle gas quality with good gas quality around 3000 RPM and above

Now, what kind of a build would i do ? for this kind of bike …

a box , rectangle, on the luggage carier, bottom one side going into a pipe downwards, pipe being the reactor.
Reactor pipe 8" or 10", 24" long

The rectangle box having 2 or more compartiments, where as the compartiment above the reactor is the hopper, the second compartment is the filterhousing with startup fan.

If someone wants to see a sketch, i can make it, but later on.


Gary’s basic Simple-fire plans are in the library of this forum under the topic of gasifier plans. Library / The Simple Fire | Drive On Wood!
Gary, Koen, and Kristian have many videos on charcoal gasifiers. It seems that Koen Van Looken has offered to assist you in the design of a small unit that will fit on the rear of your KLR-650. Yes, Yes! This is your key to getting it done right.


Hi Peter,
converting a bike to charcoal has been done occasionally during the war.
Here are some examples:

Moto Gazogène Peugeot 1942 (Salon Retromobile 2009) (you can scroll between the pictures with clicking “Précédent” and “Suivant”)
Hope you find it useful.
Best idea is to mount the gasifier on one side and the filter on the other to balance things out.
Good luck with your project!


Excellent 15+ picture set of this motorcycle charcoal system Mr Tilman. Very balanced low center of gravity layout.

One picture even shows well the system layout components flow graphic.
I tease here intentional. LOOK all of you “must have a cyclone” fellows: no cyclone used or needed.

tree-farmer Steve unruh


Great pictures and very enlightning

Notice the long stroke from the 350CC 15 HP engine ( the P112 )
On the system layout you see a “water or Oil drip” ( thats what is marked on the photo) just before the intake. On the bike however its located just left below/behind the seat. ( I did find the valves for the engine so its not a 2 stroker. with 2 stroke oil ) Trying to find more detail on the pictures.
Nozzle pointing frontwards, , flanged type with nice cooling fin’s
Crossdraft system with grate shaker and cleanout on the backside.
Hot gas filter with steel wool
After the cooler a simple cloth filter in the box

Those old days… most important lesson? they teach us that it can be done…


I was just talking with an investor the other day about adding an oil mister in to the gas. The reason, is from working the GM engineer that helped me on the V8 machines. He came from development of gaseous NG engines and said the valve seats will crack over time. They used the GM 5.7 HD vortec truck engine with the hardened seats to overcome this issue. Later on once I am manufactured developed I may add on oil mister like quads and snowmobiles have for this reason. This could be a way to recycle waste engine oil.

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Great idea for any waste oil… if injected in the hot gas stream to carburate the gas, as described in old style gasproducers, you’l get carburated gas…

Kinky dough for filtering, but it also cools down the gas to lower temperature…

Maybe hot filter, then oil mist and cyclone ?

Thinking of building a bike similar as the KLR 650 project… i have a not so old CRF250 … i have to ask my wife first :wink:


Just an idea, woodgas and straight ethanol both run best on higher compression and advanced timing. If it isn’t too late, you may want to check into a higher compression piston. I have no idea if one is available in that the KLR/PIG isn’t known as a performance bike. Yeah, I have one. They may not go fast but they do go forever!


Tilman, thats a beauty. i really appreciate the builder keeping everything mounted low

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todd, a motorcycle mechanic was just recommending an aftermarket high compression piston for my rebuild so sounds like it might be a good idea…


hey koen, thanks for the technical advice. i’ve been busy with work and haven’t had the headspace to engage for the past few days. ill look over your recs soon and probably have some questions!

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