Lp conversion?

[Wisconsintimber]

Hi guys, just wondering if anyone runs their mill on propane? 

My sawmill can sit for 2-3 months sometimes and I have had 2 different engines on it.  Gas has always plagued me and I have a 24hp Honda on it now which seems to be running lean.  It has what seems to be a lean backfire on idle and just isn't quite right under power either(better but not quite right with the choke half on). I have cleaned the carburetor thoroughly several times and proved the passages with carb spray. I run seafoam and mostly run non ethanol, but this thing just won't run right.

My question comes in because I've been looking into converting a gas generator over to Lp and wondering if it is feasible to convert a sawmill engine.  The difference is that a generator runs at a constant speed so I assume that you tune the lp flow to run properly at 3600 rpm and it works fine.  On the sawmill I would have to be able to vary the lp flow for idle vs full throttle... just a thought, looking for suggestions.

[charles mann]

Look into the info available for convertibg auto gas engines over to lp. They run a variable flow somehow. May be able to get the required valves, flow regulators and or metering valves and apply that to your mill pwr unit. 

[bandmiller2]

Wisconsin, I think it is easily done with a simple kit. Look on you tube. It would probably be more expensive to run on propane depending where you live. As an alternative make sure you have a good shutoff and drain valve under your fuel tank. Short inactive periods shut the tank valve and run dry, longer periods drain the carb and tank. A little blue marine stable wouldn't hurt. Frank C.

[Crossroads]

You may want to check your valve clearance and timing, that may be the cause of your backfire. 

[paul case]

At one time Cooks sold a mill powered by a engine on LP.

My forklifts run on propane and the run various rpm's. The only thing I wonder about is the converting liquid to vapor is done on the forklifts by the cooling water on the lift warming the lp so that it turns to vapor. On small air cooled engines that would be a problem. I bet it can be overcome.

My 4 cylinder engines on my 2 forklifts run really efficiently. I had to get a 500 gallon tank with wet line to fill bottles. I think I already am saving money though. As a side benefit propane doesnt carbon your oil up so the inside of your motor will should stay much cleaner and last longer.

PC

[Bruno of NH]

They make multi fuel generators 
Gas/Lp

[sawguy21]

After having dealt with lp in small engines I am not a fan. Valves, seats, and guides won't last as long, the fuel is very dry with no lubricating qualities. Power is reduced and fuel consumption increases because lp has less btu's than gasoline.
Cold weather operation is also affected as Paul suggests. The mixer will ice up unless warm air is directed around it. Unless you need to run the mill in an enclosed area you will likely be happier with gas in the long run.
I had nothing but grief with a multi fuel lift truck. LP dried out the carb gaskets and seals, it leaked like a sieve when they switched to gas after running out of fuel instead of checking the bottle and switching out when it got low. Finally installed a straight propane system. The crew wasn't happy about walking back to the refuelling station.

[YellowHammer]

I don't know about air cooled LP engines, but for liquid cooled forklift engines the general rule is gasoline engine rebuild after 3,000 hours, Diesel engine rebuild after 5,000 hours, and LP engine rebuild after 9,000 hours.  I've seen LP forklifts for sale with over 20,000 hours on the engine.  The long life and low emissions for warehouse work is why most forklifts run LP.  The heart of the LP system is the "Vaporizor", a low pressure heat exchanger and gas filter where the radiator fluid heats up the LP and injects it into the carb at a regulated pressure.  The vaporizor also removes the "heavy ends" of the LP, an oil/tar like contamination that clogs the carb up.  
My Cat forklift has a Mitsubishi engine that can be configured to run either LP or gasoline.  

[StimW]

This video shows how to clean the carb-  Honda GX630/660/690 Engine Carburetor Cleaning Guide - YouTube
If you go to 4:40 min it shows removing the plastic jets.
They have tiny holes in the bottom and get stopped up.
Blow out with carb cleaner.
I have not worked on this carb but have worked on many DOZENS of 8-13 hp Honda's and when that pin hole gets clogged you have to choke to get them to run.

[sealark37]

Kits are available from lift truck parts shops to convert to LP.  The kit contains an LP carb that works just like the gas carb.  You also need the horizontal LP tank to provide enough evaporation surface to run an engine.  If you run any ethanol gasoline in your mill, that is likely the cause of your problems.   Regards, Clark 

[SawyerTed]

The kits I've used for adapting small engines for liquid propane still use the stock carb.  Carb issues still needed to be solved before adding a LP adapter.  It's a good solution for small engines that get run infrequently like generators. 

[bwstout]

I installed the carb kit on m 115 kw Honda generator last winter. It is not used often but I am very well please with it. It will idle down. I also redneck an old riding mower by just going through the breather directly into the carb throat ran it for 2 years deck final gave out and junk it. I just used a adjustable regulator at the tank and the throttle work like always. I did have a video but lost it when old phone died. The kit comes with the regulator with the jet to modify the carb. You can buy kits that will allow you to use either one I just opt out for propane on mine like it.

[Wisconsintimber]

Thanks for all of the responses, a lot of good information to think about!  Thanks StimW for the video, I'll have to check the plastic jets again.

[Wisconsintimber]

my impression of the conversion kits that I see for sale is that, yes they use the carb for air regulation, but they don't use the fuel bowl or do any fuel regulation.  That is done by an external Lp regulator.

[bwstout]

There is one kit that has a snorkel that goes between the carb and intake that you do not have to modify the carb. The kit I use on my Honda gen I had to removed the bowl and the snorkel goes up through into the  throat of the carb there is no reversal unless I buy a new carb. But I have mine to use it off of the house propane tank. I have not notice any lose of power run good works like it did when it  was  new bought it in 99 after during the ice and snow storm here in East Texas that shut us down for a couple of weeks before we got power back on. Right now I use one of the small 20lb tanks.