Self taping bolt Sizes

#2
1/4" x 20 for the governor hole, 7/16" x 14 or 20 for the low oil sensor.
Don't know about using a self tapper, you may end up with metal shavings in the crankcase. Most just pull the side cover, tap the holes, and then can clean up any metal shavings.

Something else to think about if you are going to run the engine hard. You may want to add an additional breather outlet for crankcase pressure.
I just tapped the governor hole for a fitting instead of a bolt, and then ran a hose connected to the stock breather hose up to a filter.
 

65ShelbyClone

Well-Known Member
#3
I used a 1/4-20 NC set screw for the governor hole in my GX140 and might have done the same on a GX340. An M6x1.00 might also work; don't recall. The 140 got a 1/8-27NPT plug in the sensor hole.

Self-tapping bolts are going to cut awful threads and there's no guarantee they will seal completely. Are you asking because you don't have a tap & die set? If so, HF has them for chump change. Obviously the case is already open if you removed the oil sensor and governor rod.
 
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