DIR Return Create A Forum - Home
       ---------------------------------------------------------
       Chainsaw Repair
  HTML https://chainsawrepair.createaforum.com
       ---------------------------------------------------------
       *****************************************************
   DIR Return to: Stihl
       *****************************************************
       #Post#: 89658--------------------------------------------------
       MS 460 A first time Redneck fix
       By: joe_indi Date: November 23, 2022, 11:24 am
       ---------------------------------------------------------
       This 460 came  yesterday morning. New AM cylinder with OE piston
       and rings. New OE HD16 carb. It was repaired at another shop but
       they were not able to eliminate a metallic noise that was
       audible when the saw was started up. Something similar to the
       piston impacting on the cylinder when the con rod bearing is
       slightly worn. So, I removed the spark plug and carb and did my
       own test, which is turning over the engine  which if everything
       is fine should sound like what is in the video whose link is
       below
  HTML https://drive.google.com/file/d/0B62w6odJDBTwSkJXZUllYU1XVmc/view?usp=share_link&resourcekey=0-716ghng63pyUMjiUA5zpnA
       Well, it didnt sound like this more 'flat', but no sound of
       impact, but not 'punchy'
       So I lifted the cylinder to check. removed the piston (brand
       new) and slid it without the rings into the bore. Snug fit
       everywhere. Rings too had no extra gap. Crank shaft had no play
       or wear. No marks of impact on the piston top
       So, I added another cylinder gasket and put everything back on.
       My test showed a bit more punchy sound, not much, still very
       faint. Started it up. The noise though reduced a tiny bit was
       still there.
       The next thought I had was detonation from bad fuel. So I mixed
       a fresh batch  and tried, no difference.
       The only out of the normal item was the cylinder, so I examined
       it  carefully.
       I noticed that all around the bore the upper space between the
       top and every port seemed to be wider than usual, confirmed this
       by comparing the measurements with an OE cylinder. 0.2mm approx
       If I corrected this on the cylinder and if it didnt work I would
       have to replace that AM cylinder from my pocket. So I chose the
       alternative. lower the piston top to compensate!
       I used an old but got piston as a 'guinea pig' and ground a 3mm
       wide ring from edge towards the center as a slant using the only
       tool I has handy, An angle grinder with a wheel for aluminum.I
       had marked the side of the piston a 0.2mm and used the angle
       grinder all around to lower the edge to that marking.
       Not a masterpiece of machining but I had no other options and I
       had to get the job done somehow. We dont work on per hour rates
       here, ist a 'no cure-no pay' kind of system here.
       Well after this crude piston mod the sound of the engine turning
       over  as tried in the video had the normal punch. And on
       starting up I found the metallic noise had gone completely.
       Better acceleration and idling.
       I did not bother to alter the piston, but told the customer to
       keep it as a spare for the future
       And, he was  happy enough  to pay me the extra I charged for my
       efforts
       And this evening he called up to inform me that he was very
       happy with the saw now.
       *****************************************************