[Stonehenge]

I bought a laser tachometer a year or two ago to test the RPM of our cutoff saws and tub saws, and I just got around to testing it out. Operation is pretty simple; use a spent diamond blade, attach a small piece of reflective tape to the blade. Running the saw at full speed, aim the laser tach at the area where the sticker is, and it'll read out your saw's RPM.

I've posted a pic of it below. This is a 6 year-old Partner K950 cutoff saw. As you can see, it's running at just over 4,000 RPM, well below the rated 5,400 RPM.

Anyone have some suggestions as to things I might adjust or check on the saw to improve RPM?

[Bill Schwab]

I think you have two basic considerations. First, it is going to be pretty difficult to gain more RPM out of the saw blade without changing pulley sizes, unless of course your saw is in need of adjustments, or has a clogged air filter. Partner saws use a governor that is built into the ignition coil to keep them from overspeeding. As the amount of sparks per minute increases, the coils uses a rev limiter to hold the saw at what the manufacturer feels is safe enough to keep the connecting rod or crankshaft from breaking. Since you are showing 4010, I'm guessing the saw engine is not supposed to turn over 6,500 RPM.

Second, even though your blade is rated for 5400 maximum revolution, what is the optimum cutting RPM? Typically, as I understand it, running at low RPM's might save your engine, but it will trash blades. So, you need to find where that range might be. That tach is a pretty cool toy.

[NCSULandscaper]

most of the rpm ratings are done without the load of a blade on the machine, which to me would be considered false advertising.

[Stonehenge]

It is a cool toy, isn't it? Something like $50 on eBay.

I'm not looking so much to 'hot rod' the saw, just trying to think of areas where RPMs may have dwindled over the years - like cleaning out the compression release valve, because it gets gummed up, and probably is reducing compression, even when running at full speed. Possibly some refinements with the clutch, or the bearings for the pulley that drives the blade (if it even has bearings - I've never even checked!). That kind of stuff.

NCSU - I know that different mfg's measure brake horsepower and some measure horsepower - my impression is brake horsepower is the more accurate measure.

[PSUscaper]

That seems like a dangerous toy to have. I'm getting visions of a Stihl lumberjack competition where the guys are using those souped up chainsaws with those monster mufflers hanging out the side of them and cutting through 24" logs in 2 seconds............I can see it know..............Jon putting on a video clip of him running his saw at 5399 rpm and cutting through sierra step treads in 2 seconds!

I'm not sure if 'souping' up a concrete saw is a good idea, and knowing how we landscapers get, think that maybe this rpm thing might be getting a little bit carried away.......cool toy though!

[Paul]

The real test is using the tach to keep the saw running at top performance. Check out a new saw first........ see what it runs at then you can check out a older saw. I'll bet your not getting the same compression as a new saw and you might need to clean out the carb and check that the filters are clean. We used a mech tach on our saws but it worked off the spindle nut. When we bought a saw we tested it after a few hours of breaking then kept records on each one.