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Baffled by Butane

1777 Views 4 Replies 3 Participants Last post by  rbednarik
A long weekend, some spare time and what better project than to bring the Aster K4 to life. Except that I am totally baffled by the burner. With the gas valves both almost closed, I get a sustained, but fairly feeble,flame. As soon as I open the valve the flame turns yellow and leaps high. I've cleaned the jet with compressed air but am beginning to wonder if an earlier owner was a little over-enthusiastic with cleaning and managed to damage the jet.

What I really need is an idiots guide to using butane as a fuel. Does anyone know of one? Alsos where do I get a replacement jet?
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A brief from Kevin O'Connor was a key to our operational bliss of a gas fired Aster K4:

Being seasoned veteran of the K-4 firing system, I've got a few tips/tricks

First a few questions:
-Are you testing the burner outside the flue or inside? If outside, the flame will behave very different than in the enclosed flue.
-Yellow flame is usually a sign of running a lean air-fuel mixture, so the burner is not getting enough air. Have you taken a look inside the burner tube to see if it is plugged?
-Are the gas fittings leaking fuel? Be sure to check the o-rings on each needle valve for tears or rips.

Try this:
-First blow back the jet using liquid butane, be careful not to freeze your fingers.
-Open the valve on the burner 2 turns and use the valve on the tender to control fuel flow. This allows you to eliminate one variable. Re-light in the flue and try again.
-If the burner howls badly, the tank does not have enough fuel in it, and is starving for pressure. Make sure the fuel line is not leaking or being pushed off of the hose barbs.
-Make sure the tank has a chance to stabilize to room temperature, then add lukewarm water to get the tank to 85-95 degrees, which is optimal for good gas flow.

You can get a replacement jet from Aster, the part number is 10-3.
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Ryan, thanks - working back through your recommendations I think the problem is that the jet is too wide . Everything else looks fine but if I open either valve more than a 1/4 turn, the flame goes from blue to yellow. I'll ordera new jet from Hans and see how I get on. The tender also leaks and the tender suspension allows the tender to rock form side to sode with no natural center position. All in all, this doesn't seem one of my best purchases...


Sounds like you have it narrowed down. Gas Jet seems most likely to me as well.

Don't give up! The K-4 is a very agile and strong engine...I was able to walk off with 24 loaded MDC hoppers (10 lbs a piece) with nary a hitch or slip of the driver. The major thing to remember is to always keep the water glass full! These boilers had the glass mounted 1/4" lower than they should have, so all readings are 1/4" off on the glass. Replacing a boiler is not the funnest task, either. Other than that, they are very good engines, docile and easy to operate.

Leaks can be sealed up fairly easily. In the interim of waiting for parts from Hans, maybe focus on getting the tender leak-free? As for the side-side issue, I have a solition for you. Get some colt .45 caliber pistol firing pin springs, disassemble the truck and cut the firing pin springs to length, then replace two of the OEM springs with the new firing pin springs, be sure to stagger them diagonaly across from one another. This stiffens up the tender trucks and helps prevent the side-side rocking, not to mention the dreaded rear end sag that occurs as the springs age, causing the coupler to drop down.

You can contact me off list (TR3services/at/gmail.com) if you become truly stuck. Always glad to help.
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