RE: Setting up an OS 1.60, cline, bisson pitts, 18x6w
G'day Mate,
Why did you cut the ends off the muffler tubes, sounds like your idle is a bit lean, try the pinch test at idle, it should increase revs very slightly, before dropping revs, if it just dies it is too lean, go back to an OS8 plug & try an APC 18x8. 18X6 may be a bit underpropped.
I run a 160FX with an OS8 plug 10% nitro, & bisson pitts muffler, as supplied, no pump or regulator & swing a 16X10 APC, pulls my 12lb Katana, vertical from take off, & no hesitation.