Hi I have a jetting question. I have a Walbro LMT37 carb from a briggs 12.5hp motor, i just aquired a rebuild kit for it which came with 4 different nozzels(main jets) a blue one, green one and two brass colored ones with a smaller jet hole in one and the other with a larger one. My carb calls for the brass one with the smaller orifice, I believe the larger orifice jet is for a set up with an adjustable mixture screw thru the float bowl. would one of the other jets give me better preformance or is there any modifications i should make to the jet like drilling it out to gain a little better carb response or performance. my motor for the most part is stock, no cam or internal mods. it does have the timing advanced using an advance key and is ported and lower back pressure on the exhaust and a better airfilter(uni). I will be running this un-governed. I'd appreciate any input that you may have.
Thanks