Question for 5twins

[hotshoe]

It seems from reading in this forum that you are the resident expert on tuning carburetors. I am building a Street Tracker starting with a 1979 XS 650 special. I wanted to run the stock air cleaner set up and after investing in new filters, all rubber boots, and powder coating ( about $300.00 ) I find they wont fit under my Omars fiberglass seat rear fender combination. I have to run the K&N round style air filters. Can you tell me what jet and needle settings I should purchase and start out with? Your help would be greatly appreciated.

 

[5twins]

I'm going to assume you're using the stock '79 BS38 carbs? If so then first thing, don't use K&N pleated type pods. They don't work right on CV carbs and will give you lots of tuning headaches. Use UNI straight foam pods, for the BS38s the part # is UP4200 or UP4200ST (dual layer). I can't tell you what will be exactly right but can give you a starting point. The pilots will need to go up 1 to 2 sizes, so get some #30s and #32.5s. You need the VM22/210 type pilot jet. For mains, you will probably need 2 to maybe as much as 4 sizes up. I would start with #140s and #142.5s. With the larger mains, you will need to lean your needles a step. Stock setting is the #3 or middle needle clip slot. Move the clip up 1 to slot #2. This will lower the needle in the slide and make it leaner.