Rpm Limited Coils

[KE4AVB]

Well I knew rpm limited coils were being used in chainsaws but they now appearing in the string/brushcutter line now too so it is possible to have the same problems of cut outs at full throttle if you exceed the max rpm set limit.

These manufactures are making the low end stuff so cheaply and of lower quality parts that they must limit the upper rpms to prevent damage. It is also most likely to meet government regs much like maximum blade tip speed we have on mowers. Limits like how far the string trimmer can throw a peddle or how fast a chainsaw can cut you leg off.

On the chainsaw cutting off your leg I wonder if that is a properly sharpen chain or a dull chain. I get chains in so dull that they are basically de-barkers.

[RoyM]

Pretty hard to over rev a trimmer if the proper line is used and trimmed to the correct length but yeah it has to do with emissions and safety. We would see commercial units come in with the guard removed, the clutch would be overheated from slipping and complaints of no power.

[KE4AVB]

Now I have seen those Stihl FS90s without the string guard too but the only string trimmers I have seen with clutch problems have been some of the low ends that idle speed was set too high leaving the clutch partially engaged. I did see one Craftsman hedger that shook itself apart from running at 12000 rpms when it was design to go only 9600. The only way to limit its top speed was to run the engine richer than it should have been. The same that I do with Stihl chainsaws that are over revving out of the cut.

Now Husqvarna chainsaws they do run limited coils but many can be converted to unlimited coils if you which coils to use. The biggest safety issue I have with chainsaws that used correctly is improperly made chain loops and damaged chains from sharping with chop saw type chain sharper/grinders.