Mystery missfire .

[john charlton]

My 31 CCPU decided it would idle on 3 cylinders . Found no.4 was not firing . Checked the plug it was oily so had not been firing . Changed the plug but no change . Did a cold compression check 1,2,and 3 all show 52 PSI . No 4 shows 60 PSI . I thought higher compression due to oily cylinder . I then got to thinking it has spark it must have gas as it shares the inlet tract with no 3 which runs fine . I pulled the leads off 1,2and 3 and see if no 4 would fire ,after full choke briefly no 4 fired up and idled DONKA DONKA DONKA with a bit of throttle . I put the leads back on the other cylinders and it idled on all four as it should . Gave it another try today but it is back idling on 3 .Although I did expect this, I am now a puzzled 81 year old . There has to be a logical explanation but right now it escapes me . Could be bad gasket. I will investigate further and let you know if I solve the mystery .

John in its been raining nonstop for three days and gusts to 60 MPH and I should be in my snowbird trailer in sunny Chandler AZ DRAT !!! And I just paid my ground rent till April 2021 !!! Still in Suffolk County England thanks to Covid 19 .