I was wrong! Unfortunately, I believed something I read a few years ago when reading online discussions about tachometers. Some of the posts suggested that the Stihl tach refresh rate was too slow, and there was a risk of overheating because it would take too long to actually see the current RPM number displayed when tuning chainsaws.
Because the factory settings for OEM carburetors are so precise, I spent little time learning the process of properly tuning a chainsaw. The other Stihl tools usually have ignition-based limiters or attachments that keep the RPMs from exceeding recommendations. I received an MS660 a few weeks ago, so I wanted to be sure that this rebuild worked precisely. I DO NOT want to tell my boss that I smoked a piston/cylinder kit that MSRPs for about $260, or have a customer return for warranty work due to faulty repairs!
Once I spoke to someone who's done this for many years, he explained how to use WOT bursts to tune the high end. He also recommended going slightly lower than factory specs before setting the limiter caps. Since I bought the EDT 7 instead of the EDT 8 for my tool set, my tachometer has a high speed save feature that makes it more convenient to tune. Before tuning, I decided to open the high circuit 1/8 just to be safe.
The low end was within manual specs. The high end took four small adjustments to lean it up to my desired rate. It repeated the same rate on the next burst. A follow-up inspection through the exhaust port looked great. After this rebuild and a very happy customer, I can't see why the Stihl tachs would receive any criticism.