PulsaJet carb question

[PensFan]

My older Craftsman edger is equipped with a 3.5 hp B&S engine. It had been surging at no load. Bought a genuine B&S carb kit and installed it. Problem is better but not gone. This carb doesn't seem to have a mixture adjustment screw. Based on my Googling I suspect it has a "pilot jet." The kit included mixture adjustment screws for various models but nothing that fits my carb. Has anyone here ever come across a carb like this?

 

[Hammermechanicman]

Pic of carb?

 

[PensFan]

This is a picture from the Internet. Mine looks just like this.

 

[PensFan]

Here's what the "adjuster" looks like. It's all the way in.

 

[Hammermechanicman]

Look at the end of the "adjuster" for a small hole. That is the low speed jet. Make sure it is open and clean.

 

[PensFan]

I'll do that tomorrow.

 

[PensFan]

Checked the very small hole and found it to be clear. Engine still has a slight surge.

 

[Rivets]

Two things I would check. Did the kit come with a new pump diaphragm? Did you install a new gasket between the carb and tank. Remove the carb a see if the small auxiliary tank is full of fuel. If not the seal may be compromised and leaking. This will not allow a steady amount of fuel in the auxiliary tank.

 

[PensFan]

Two things I would check. Did the kit come with a new pump diaphragm? Did you install a new gasket between the carb and tank. Remove the carb a see if the small auxiliary tank is full of fuel. If not the seal may be compromised and leaking. This will not allow a steady amount of fuel in the auxiliary tank.

Yes, the kit included a new diaphragm (fuel pump). Yes, a brand new gasket between the carb and tank. I would like to avoid taking the carb off again. It's a big pain in the behind.

 

[slomo]

I would check the carb intake manifold to block. Briggs uses really thick gasket like 3/16" or thicker there. Chinese Amazon/Ebay carbs come with half the thickness of a Briggs gasket. That is step 1.

Step 2 is lap the intake manifold face and engine block areas. Every manifold I've seen is warped. Weight of carb and manifold hanging in the air with all the engine vibes over time. 220 wet/dry paper with soapy water on a sheet of plate glass. Go 400, 600 then 800 grits.

Make sure the fuel pump (spring and diaphragm) plunge into the body cleanly and evenly. I've had some Chinese ones that needed some metal massaging. Make sure it gets the full plunge travel as well.