Ok guys, I'm needing some help here. I was given a non running, but complete Stihl 066 Magnum. According to Holmen Tree's info, its a dog eared 1997 model, I put fresh gas in it, new properly gapped plug, pulled it and it won't fire. So, tested it at nite with a test light, no fire. So, since it has the unlimited coil, I figured that was the problem. So, I ordered a aftermarket replacement. But, it's only got one leg, instead of two. Set the gap to .011", tried it again, still won't fire and run. So, tested it with the test light, and test light lights up. So, what gives? I know it will need a carb rebuild or a aftermarket one, but, I was putting a very small amout of fuel mix directly into the carb. So, it should have at least fired. Compression is very low, as it will slowly unwind the starter cord with the decomp out. So, I'm needing some suggestions, thanks.
It sounds like you found the problem. Remove the muffler and look at the piston skirt, it is likely scored/galled. An 066 should not drop against compression. Before you tear into it do a vacuum/pressure test to determine if there are air leaks, no point replacing the top end only to have it fail again.
Agree.....going into a saw blind like that...pull the carb and the muffler to have a looksee at the piston/rings and cylinder. Also consider that if it was owned by the 'no warm-up' crowd, there could be aluminum transfers you can't see...usually between the carb and exhaust cylinder side somewhere.
Low compression on a decently low hr saw can only come from stuck rings, aluminum transfers, corroded decomp etc....but yeah, do a complete vac and pressure test on the saw too. Besides the crank seals, consider a leak in the carb boot and/or impulse line.
Kevin
Thanks guys for the info. You are both right, the cylinder and piston and rings are shot! However, upon further inspection of the saw I found the pto side case broken in two, one break where the clutch shroud screw is and another on the bottom in front of the rear av mount. Unfortunately, i don't think this saw is rebuildable without spending a lot of money and time on it. Thank ya'll again for the good info!
OK. How much you want for it. Im not scared.
Welder, I looked at it some more and think I can repair the broken part with something like super duty liquid steel after putting a metal strap along the side and rivet the strap into the saw. If it doesn't work, I'll let you know. Thanks for asking.
I have an 029 that I tried to fill in a spot with JB weld. That didnt work . Let me know.