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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

    Joined:
    Dec 14, 2011
    Messages:
    276
    Loc:
    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

    Joined:
    Oct 25, 2012
    Messages:
    2,188
    Loc:
    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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