Subaru SP170DT1150 on a Rigid air compressor. Has a Mikuni carb on it, with idle mixture screw. Fairly sophisticated for a small engine carb. From what I've gathered it is very similar to the Subaru EX17 engine.
This engine has had a multitude of issues lately. It got a brand new carb installed this last summer. Then a piece of plastic jammed the intake valve open (no idea how it got in there) and the head had to be removed to get the plastic out.
On reassembly the engine will not start without carb cleaner or some form of fuel shot into the intake. Once running it seems fine. It is on an air compressor and it will charge the air tanks and then go back to idle just fine. However when the compressor calls for the engine to spool up it pops the throttle to WOT and the engine instantly dies. If you slowly open the throttle it is fine. But sudden jerking kills it, and the compressor opens it with a spring loaded device to WOT instantly.
The carb is clean as a whistle, it is virtually brand new with only a few hours on it. I put some copper through all the jets and shot carb cleaner around, still no go. I found a spec online stating that the idle mixture screw is supposed to be 1.25 turns out. When I drilled the plug out that covered it I found it to be fully seated. I turned it out to 1.25 after completely removing it and cleaning behind it with carb cleaner and compressed air.
The only part of this carb I have not removed is the emulsion tube. I can't find a spec for the float height anywhere online as of yet.
The difficulty in starting from cold (and hot) and death when the throttle opens indicates to me that it is running lean. The intake gaskets are new, and the air cleaner is installed. Anywhere else I should be looking to get this running properly?
I'm open to suggestions at this point.
This engine has had a multitude of issues lately. It got a brand new carb installed this last summer. Then a piece of plastic jammed the intake valve open (no idea how it got in there) and the head had to be removed to get the plastic out.
On reassembly the engine will not start without carb cleaner or some form of fuel shot into the intake. Once running it seems fine. It is on an air compressor and it will charge the air tanks and then go back to idle just fine. However when the compressor calls for the engine to spool up it pops the throttle to WOT and the engine instantly dies. If you slowly open the throttle it is fine. But sudden jerking kills it, and the compressor opens it with a spring loaded device to WOT instantly.
The carb is clean as a whistle, it is virtually brand new with only a few hours on it. I put some copper through all the jets and shot carb cleaner around, still no go. I found a spec online stating that the idle mixture screw is supposed to be 1.25 turns out. When I drilled the plug out that covered it I found it to be fully seated. I turned it out to 1.25 after completely removing it and cleaning behind it with carb cleaner and compressed air.
The only part of this carb I have not removed is the emulsion tube. I can't find a spec for the float height anywhere online as of yet.
The difficulty in starting from cold (and hot) and death when the throttle opens indicates to me that it is running lean. The intake gaskets are new, and the air cleaner is installed. Anywhere else I should be looking to get this running properly?
I'm open to suggestions at this point.
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