Author Topic: Walbro carb Jetting  (Read 5932 times)

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taz_tickle

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Walbro carb Jetting
« on: January 30, 2006, 08:01:06 am »
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

Offline George Herrin

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Walbro carb Jetting
« Reply #1 on: January 30, 2006, 11:03:53 am »
the nozzle with the larger hole is for a carb that come with a seperate tiny main jet that screws into the side of the tube where you screw the nozzle in. Where yours uses the smaller hole nozzle the hole in the side is not threaded for the tiny main jet. Being mostly stock you may be best to leave the jetting where it is. However you can use the larger hole nozzle and order an adjustable needle assy. screws right into the bottom of the carb allowing you a wide range of main jet adjustment. The part number is 100-506. You can call me here at work 615-446-6807 for the priceing I do not have the price sheet in front of me nor do I remember off the top of my head.
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taz_tickle

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Walbro carb Jetting
« Reply #2 on: January 30, 2006, 12:24:47 pm »
Thanks for the info. I think for now I'll stick with the original set up till I decide to put a cam in it, at that point I may consider some more extensive carb work.

 

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