Working on it for a good friend. It started but would not spin up consistently or well. Compression was 145. Found a cracked impulse line and replaced it. Also replaced crankcase seals for good measure. Passed P and V testing well. Points were suspect so installed a chip. Saw then accelerated, started (cold and warm) well and idled Ok. But it would not come down off WOT immediately. Went back at it and snugged up a marginally tight intake boot clamp. Fired it up again but then it quit suddenly. No spark. I had another chip. Installed it and spark was back. However the saw then struggled to start and when it did it died quickly. I then noticed the chips were slightly different. The photo shows the chip that worked for a while then failed. It is marked with a red x. The unmarked replacement chip that did produce spark but made the engine struggle is definitely smaller. Its mounting hole is in a different location and I had to drill it a bit larger to accept the coil bolt. Are these chips designed and produced to differ in performance spec and is one specific to Stihls like an 028 WB?
