Kurt fired it up today and it sounded like a REALLY loud rap like a really loose lifter on a chevy.
You're there to hear the noise, I'm not... but...
A rod (bearing) doesn't normally just "go bad" between shutting the engine down at last use and firing it back up. The CH15 uses hydraulic lifters, and if one of those gets stuck the engine will rattle like rocks in a metal can. I'm not a believer in fuel and oil "treatments" as a general practice... but I do use them if the situation warrants. A gummed-up and stuck, or sticky hydraulic lifter can real often be cleaned-up and "freed-up" by using Sea Foam in the crank case oil... I've seen it work dozens of times. Usually I change oil and filter when adding the Sea Foam (I put a bit more Sea Foam in than what the label recommends), then run the engine something over idle speed (varying from ¼ to ½ throttle) for a while... you can actually hear it working, the noise just fades away. I normally run the engine another 15 minutes or so after the noise is gone, shut it down and allow it to sit overnight to do it's "gum-removing" thing, then run it again for another 30 minutes or so before changing oil and filter again. If the lift doesn't quiet-down during the first run (say, after 30 minutes or so), it often will during the next day's run.
Oh... I use 10w30 in all the engines (small and large), I buy it in 2-gallon jugs at the fleet store... it's Mystik JT-8 brand, heavy duty diesel synthetic blend. I don't buy it because it's a "heavy duty" oil, or a "diesel" oil, or because it's a "synthetic" blend... I buy it because the 2-gallon jugs are the best damn price-per-quart of any on the shelf. I didn't use a "synthetic" of any sort until the last couple years... but now the synthetic "blends" are as cheap, or cheaper than the 100% dino oils (if you can find them). The small engines I use during mid-winter get switched over to a 5w20 sometime in December, and back to 10w30 in late March/early April.
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