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Tach reading after muffler mod.

Post in 'The Gear' started by Wildo, Sep 10, 2013.

  1. Wildo

    Wildo Feeling the Heat

    Dec 14, 2011
    jackmanistan, maine
    I have been wondering what my saw should tach. at now that it breathes better. I removed the tube from the muffler and increased the area by 65%+/- as well as put holes in cat 3x3/8" . So after I unchoked my 2152 and richened it up to gurgle/4stroke by ear I was wondering what the rpm's should be, stock top is 13,600 and it was 13,167-13,204 before (at last checkup last year) now it rips but it seems like the rpm's are lower to my ear. I consistently ran 91oct plus booster to 100++and amsoil interceptor since it was new at around 40:1/48:1 . I am currently running 100 oct and 36:1/40:1 to be safe till I can figure it out to where I want it. What is a good tach. number after modification? Where is a good cheap place to find a tach?

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  2. MasterMech

    MasterMech Guest

    Every saw is an individual. If it's four-stroking then it's not too lean and I wouldn't worry about the no-load RPM's. What matters is if it's pulling more R's in the cut. If you'd like a little more power, try less octane. Unless you have boosted the compression via a base gasket delete or squish mod, then all the extra octane above whatever the mfg specs (89?) is unnecessary and actually robs you of power. Try running a batch of 91 without the booster, betcha it runs just fine on that and $$ saved as well. Interceptor at 40:1 - 50:1 is just fine as well, I wouldn't change that unless you wanted to switch oil types/brands.

    When I did the dual-port mufflers on the MS460's, setting them to factory limits of 13,500 resulted in them running pig rich really. Saw would rather have 13,800 or more. I initially set them in April with an outside temp of about 30::F and the next time I went to use them it was 70 deg out and they were so rich, they barely ran.
    clemsonfor likes this.
  3. HDRock

    HDRock Minister of Fire

    Oct 25, 2012
    Grand Blanc, Mi
    Best way I have found to tune , is tune it best U can , then put it in some wood, adjust , then put it in some wood again, till U get it right
    Wildo, clemsonfor, Boog and 1 other person like this.

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