Carb Adjustment

VortecZ71 · Jun 16, 2012

I just had a new Walbro carb put in my Simplicity Regent. I think it needs a little adjusting. I think its getting too much fuel at full throttle. Can you tell me which screw does what in the picture of my carb below. Chris

RandyT · Jun 16, 2012

The screw at the top is for adjusting the idle speed. Most of the newer carbs just use that screw to prevent the throttle from slamming shut and stopping fuel and air flow, because most now use a governored idle. the bottom screw is for adjusting the idle fuel mix, may have a minor effect on the top no load fuel mix, but little to no effect under load, ie, blades engaged.

VortecZ71 · Jun 16, 2012

How can I adjust how much fuel it gets at full throttle then? After the tractor warms up and I put it at full throttle it sounds just like if I was to put the choke on. It's even worse when the blades are engaged. If I lower the RPMs a bit, the engine runs a little smoother.

Also, does turning the idle screw clockwise increase or decrease the amount of fuel.

Jim Thompson · Jun 16, 2012

The idle screw has no effect on the amount of fuel. It is a speed adjustment only. The other screw will have minimal effect and only at idle. Those are usually set at approximately one and a half turns ccw from fully seated. I don't recall ever having to adjust one after a rebuild. The carburetor may be defective or you may have other issues. A stuck float or trash keeping the needle valve open could cause the engine to run rich. A dirty air filter could also cause your problem although I wouldn't expect that the shop would reinstall a dirty filter on a new carb.

Jim

VortecZ71 · Jun 16, 2012

Jim Thompson said:
The idle screw has no effect on the amount of fuel. It is a speed adjustment only. The other screw will have minimal effect and only at idle. Those are usually set at approximately one and a half turns ccw from fully seated. I don't recall ever having to adjust one after a rebuild. The carburetor may be defective or you may have other issues. A stuck float or trash keeping the needle valve open could cause the engine to run rich. A dirty air filter could also cause your problem although I wouldn't expect that the shop would reinstall a dirty filter on a new carb.

Jim

The carb is brand new as is the air filter. The tractor runs perfect for the first 10 or so minutes. It seems I start having issues once the engine gets warmed up. If I turn down the RPMs for whatever reason such as to get off the tractor and then turn it back up to full throttle I start having problems. I did not have this issue before the new carb. The shop installed a new one because the tractor would dump fuel out of the exhaust at startup. BTW, its an older simplicity with the 14HP Kohler Command.

Jim Thompson · Jun 16, 2012

VortecZ71 said:
The carb is brand new as is the air filter. The tractor runs perfect for the first 10 or so minutes. It seems I start having issues once the engine gets warmed up. If I turn down the RPMs for whatever reason such as to get off the tractor and then turn it back up to full throttle I start having problems. I did not have this issue before the new carb. The shop installed a new one because the tractor would dump fuel out of the exhaust at startup. BTW, its an older simplicity with the 14HP Kohler Command.

Very familiar with both the tractor and the engine. You may want to return it to the shop that did the carb replace. If you want to try to correct the problem yourself, you may want to check the linkage that controls the choke to insure that the choke is opening completely.

Jim