When it's cold (below 40) it will not fire. in the past, using starting fluid would get it going, but not now. it makes no attempt to fire. however, if the temps are up (remember the 60s & 70s we had not too long ago) it starts immediately. this is what i've checked/done thus far. recent: fresh fuel, two new spark plugs, new coil and wire. (did not replace plug boot - resistance measurement was within spec) last summer - new magneto any suggestions??????