Propane

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Gordon

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I am attempting to run an engine on propane. I have tried in the past and could never get it to work. In looking at the information available I am just getting more confused. I have an adjustable regulator from a gas grill and I have a demand valve made with the Tecumseh diaphragm. The first question is should I be going for the low end or the high end pressure range? The next question is the carburetor used. Should I be looking for more flow or less flow? Do I want a smaller or larger orifice and a smaller or larger throat diameter? The engine that I am trying to use it on is 1.25 bore if that is important.
 

maury

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Gordon, I don't know how a home made demand valve would work. I use one I bought for use in a
truck. I use a BBQ grill regulator to lower the pressure in front of the demand valve.
You need to change your thinking about how a mixer/carb works with a demand valve. If you are having trouble, the chances are your problem is the mixture is too rich. It won't ignite if it's too rich.

So, air being pulled in through the mixer during the intake causes a vaccuum on the propane orface, and pulls a little gas in with it. Very little. At all other times there should be no gas flowing into the mixer.

If you are using a adjustable regulator, put it on medium or low, though if you have a good demand valve it probably won't matter.

I believe the demand valve i have is a Garrett.

Hope this helps
maury
 

krakkah

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I am attempting to run an engine on propane. I have tried in the past and could never get it to work. In looking at the information available I am just getting more confused. I have an adjustable regulator from a gas grill and I have a demand valve made with the Tecumseh diaphragm. The first question is should I be going for the low end or the high end pressure range? The next question is the carburetor used. Should I be looking for more flow or less flow? Do I want a smaller or larger orifice and a smaller or larger throat diameter? The engine that I am trying to use it on is 1.25 bore if that is important.
In my experience gassing GX25 engines its almost always rich! Imagine mouse fart and divide by 2!. You dont need much. There is some sweet systems for these engines for running indoors. Good designs to copy from.
 

Rustkolector

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Gordon,
I use propane and try to keep it simiple. I use a Weber Go Anywhere gas grill 1 lb. bottle regulator. It's a constant pressure (~ 4" water column) adjustable flow regulator. You don't need much pressure. I use Jerry Howell designed demand regulators. I try to find self compensating RC carbs with the smallest barrel opening. The needle valve setting will be 2-4 turns more open with propane than it would be with gasoline. RC carbs with an adjustable air bleed will also work.

Put the demand regulator hose leading to the carb in your mouth and very gently suck on it. It should let propane flow with with a very gentle vacuum signal and stop propane flow without a vacuum signal.

Propane probably works best with hit & miss and constant speed engines. Variable medium speed range engines will work also, but generally won't have a very have snappy throttle response.
Jeff
 

Gordon

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I have a gas grill regulator and I have built the Howell demand valve. I have tried several carburetors but I have not had much luck. I guess that I should experiment on an engine which I know runs well. I have been trying it on the Atkinson Differential which I have never been able to get to run more than a few pops. The engine keeps flooding so I thought that with propane at least it would not flood and foul the plug.
 

Harglo

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I am attempting to run an engine on propane. I have tried in the past and could never get it to work. In looking at the information available I am just getting more confused. I have an adjustable regulator from a gas grill and I have a demand valve made with the Tecumseh diaphragm. The first question is should I be going for the low end or the high end pressure range? The next question is the carburetor used. Should I be looking for more flow or less flow? Do I want a smaller or larger orifice and a smaller or larger throat diameter? The engine that I am trying to use it on is 1.25 bore if that is important.
Hello Gordon.
I run all my engines on propane with man problems with the home made carbs haven't found others at this point some due use a RC or other. Your talking about no flooding with propane. Well If my engines don't start I open the exhaust valve an turn them over several times close the valve an they start. So seems they can an do flood with propane. Its interesting to note how little propane is needed to run them. I have a propane station with 4 ports use the chain saw carb parts only cause there smaller.
Harvey
 

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