Yes, you'll need to drill and tap the back cover. It's easy, you can do it. Just buy a drill bit and tap combo so you have the exactly right size, and drill the hole carefully and straight. If you have or can borrow the use of a drill press, that would be great but it's not necessary. If you have some small drill bits, it is always best to drill a smaller hole first, then open it up to the size needed for the tap with the tap drill bit. Then lubricate it with a light oil, make sure the tap is straight, and go slowly. After each turn of the tap once it is well started, back the tap out about a half turn.. This helps clear out any chips. WD-40 actually makes a good lubricant for tapping aluminum. It won't hurt a thing to add a touch of JB Weld to the pressure tap when you screw it in, but trial fit it first, and be sure to clean the pressure tap and your new hole with carb cleaner or acetone before installing with the JB Weld. You'll do fine.

Just to be sure we are on the "same page" about the pressure tap for an external pulse line on the carb itself, here is a pic of a Stihl 62cc that I converted, and a Homelite 30cc that I converted and hopped up that shows the location of the tap. (Don't have a pic of my Supertiger .90 converted to gas with a Walbro on this computer.)

As an aside, note that the Zama carbs are just slightly smaller in outside dimensions, and this sometimes help when you have a really tight fit. I prefer the Walbro carbs myself though.



AV8TOR