Have a question about a briggs quantum carby (primer not choke). The engine is a XTS 50 from 2003. It’s in good condition and worked alright when I got it, but surged from cold. It was a bit better when warm. Anyway through one reason or another (partly because I infinitely prefer mowing with Victa 2 strokes) it sat for 3-5 months.
Went to start it last week as I thought I should, but I was too late – clogged carby. I will be installing a fuel tap shortly – they should come from the factory with one.
Ripped it apart and cleaned it out, and ran, but still surged badly when cold and somewhat when hot. Tore it down again and gave it an extra thorough clean, with only slight improvements.
The plug electrode is white (and always was white), which of course means its lean – also explains the surging. Checked the o rings, and cleaned all mating surfaces – no leaks.
My query is, where are the hidden mixture adjustment screws on this carby. They must be there somewhere.
There is a ball bearing plug on the carby (as shown in the picture), I am thinking of drilling a small indent above the ball bearing, so I can lever it out with a screw driver.
I am guessing there will be an idle mixture screw – but I don’t want to just open up a fuel passage.
If it is the model you it is a fix jet model, no hidden adjustment. You need to resize the main jet a few hundredths of a mm. Resize in baby steps. The main jet is part of the fuel retaining bolt. I had to this to several engines on garden tillers.
If it is the model you posted it is a fix jet model, no hidden adjustment. You need to resize the main jet a few hundredths of a mm. Resize in baby steps. The main jet is part of the fuel bowl retaining bolt. I had to this to several engines on garden tillers.
Tyler did this make sense to you? I know I left out a couple words which I added to my quoted text in red.
I worked on it yesterday, and drilled a indent above the ball bearing plug and levered it out. Thankfully I didn't damage it as there is no mixture screw under there as you said.
The model is 12F802 3112 B1. Date code 03071756
Cleaning it out extra well a third time has resulted in the plug electrode going from white to a more brown colour. Adding a small cylindrical piece of oiled foam to the top air filter (has a snorkel) solved the problem completely - just made it run that little bit richer.
One day I will probably end up resizing the main jet.
