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Modding Stihl 036

Discussion in 'Chainsaw' started by chevy_tech, May 16, 2008.

  1. chevy_tech

    chevy_tech ArboristSite Lurker

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    I'm new to the world of modifying chainsaws. I have an 036 with 16" and a 20" setups. I removed the front cover of the muffler one day and drilled two 3/8" diameter holes in it in front of the exhaust port. It got a little louder and seemed to have more power. My question is, is it safe to keep opening up the exhuast or should I leave it? I havent touched the carb yet and was wondering how I should adjust it for the mod that I have done. Thanks.
     
  2. Haywire Haywood

    Haywire Haywood Fiscal Conservative Social Retard

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    Do a search for "muffler mod" and read read read. You're missing one vital step after drilling those holes. Oh, and don't run your saw again till you accomplish that last step, it's possible that you'll kill it if you do.

    Ian
     
  3. romeo

    romeo Addicted to ArboristSite

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    Stick within about 80% size for all the muffler ports together of the exhaust port on the cylinder. You will be safe.
     
  4. timberwolf

    timberwolf Addicted to ArboristSite

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    Safe??? Not if he doesn't retune the saw...As haywire points out.

    Intersting first post....ya thinks?
     
  5. OilHead

    OilHead AboristSite Guru

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    Go ahead & open them up to 5/8 " but only if you plan on pulling the carb. Remove the limiter caps & make sure your "pop off pressure" isnt above 19psi. Anywhere between 15-19 psi is good. Install a new carb kit unless it has recently been rebuilt if it has'nt then the diaphram wont be in exact calabration & you may just find some very fine saw dust accumulation inside the fuel pump area. Then set the saw to 13,400 rpm , 400 over max recommended & get a 9 pin rim sprocket from madisons. Doing this will incease your chain speed 20 ft. per second more.

    You'll have to add 1 link to you chains.
     
  6. timberwolf

    timberwolf Addicted to ArboristSite

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    an 036 pulling 9 tooth 3/8:confused:

    You would be doing well if it could pull an 8 pin gear on a 20 inch bar. Stock with a muffler mod 8 on a 16 inch bar would be touch and go.
     
    Last edited: May 16, 2008
  7. OilHead

    OilHead AboristSite Guru

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    I should have mentioned my 036 has 044 dawgs on it so the 16" is closer to being a 14.5 " & I pick up a bigger saw if the branch is bigger than 12". It's pretty much commited to just being the limbing saw 4" on up.. Really like the zing though. :chainsaw:
     
  8. timberwolf

    timberwolf Addicted to ArboristSite

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    Now is that running syntetic oil at 40:1?

    Falling trees faceing south so the saw engine is working with the coriolis effect of the earth's rotation too?

    Even ported 70cc saws struggle to take advantage of a 9 pin 3/8 gear.
     
  9. weenieroaster

    weenieroaster ArboristSite Operative

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    Agree on the 9 pin being problematical. You can get very good torque out of the 036 by modifying, and a very functional saw in big wood with a 7 pin.
     
  10. OilHead

    OilHead AboristSite Guru

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    When I built this really wanted something lighter like a rear handle MS 200 for the limbing saw but opted on an 036 instead . Probably should have built a 084 for as much as I got in the thing , but needed something a little lighter with some real guts. One saw builder told me that with a complete woods port job with transfers & muffler it can run a 10 pin with the 16" bar. I run the 9 because the saw is producing hp right up there with a stock 044. No transfer work though. Have tested it in 12" oak & it is fast. Then grab a bigger saw if you need a longer bar. 45/1 ultra - 92 octain. Hey : Weinner Roaster have you completed all your testing with pop off pressures ? :chainsaw:
     
  11. weenieroaster

    weenieroaster ArboristSite Operative

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    OilHead, yes I have tested about all the saws I can get my hands on. From what I have found, if the carb makers are paying any attention at all to the pop-off pressure on their carbs for stock saws, they must be on a secret mission to conceal their knowledge...ie, the pop-off pressures are all over the board. A 242xp that I tested today, had a pop-off pressure of 34psi! More often than not, I'm finding stock pressures above 20psi. Don't know if you saw the email I posted from Walbro on the subject.... Basicly, a
    guy there said it doesn't matter on stock equipment, but did go on to say that in racing engines, like in karting, the pop-off is more critical. I guess that they think it is out of their jurisdiction to have to respond informatively to any question that goes beyond stock engine requirements. Unfortunately, they act totally vague on the subject. I still haven't exactly settled on what I find is best for my modded saws, but I doubt it is 34psi.
     
  12. teacherman

    teacherman Addicted to ArboristSite

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    This of course is the most important factor...a great increase in engine momentum, but may need to tune it back a bit to avoid overrevving....:biggrinbounce2: :Eye: :p
     
  13. teacherman

    teacherman Addicted to ArboristSite

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    Pop-off pressure? Whut's thayat?:dizzy:
     
  14. weenieroaster

    weenieroaster ArboristSite Operative

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    If you hook up a pressure tester with a pump to the fuel inlet of the carb, you can determine what amount of air pressure is required to overcome the spring tension and move the metering needle off it's seat. That pressure is the "pop-off". Greater or smaller spring tension has the most ramification at low end rpms. It's not critical for stock engines, most folks claim. Whatever the case, it's adjustable.
     
  15. wanab

    wanab Addicted to ArboristSite

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    its how much pressure your unit will take before it pops.


    ooops, sorry couldnt help myself.


    :greenchainsaw:
     
  16. teacherman

    teacherman Addicted to ArboristSite

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    Thanks. I will not likely get into it at that level, but it's nice to know. I am getting ready to vac test a crankcase for th e first time. I am gonna try sealing the muffer and manifold with Gorilla duct tape just to see if it works.. will report back. Y'all have a good day!:greenchainsaw:
     
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  17. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Try cutting out a piece of bicycle inner tube and bolting the inner muffler on over it.
     
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  18. OilHead

    OilHead AboristSite Guru

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    Ha . Have to agree . It just seemed mighty suspicious from the start not being able to to find the manufacture specification . Makes me wonder how long it's been going on. So whos got some vintage chainsaw service manuals ? One thing I did notice when performing the mod was the 310 w/ the walbro has a much larger diaphram & venturi than the 036 w/zama. That may partialy explain why were finding major differances because of the sq. effect X . Also after removing the inner muffler cage that they put & incresaing the dime sized exhaust everything changes from a backpressure situation to more scavgeing. So getting more fuel becomes & issue you cant make real hp without it. Next I guess we'll have to do something about these choking for air filters. :chainsaw:
     
  19. Lakeside53

    Lakeside53 Stihl Wrenching

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    Just loosen the muffler and carb, slide a piece of truck inner-tube rubber down behind it... retighten.. Sealed...
     
  20. Lakeside53

    Lakeside53 Stihl Wrenching

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    I betting that the carb manf have it figured out.. the spring used on the Zama 036 is used on many base carb types, over a 100 models of weedeater, saws and blowers, over 20+ years of production (way way before the epa got involved), and that's just with Stihl...

    The walbo springs can vary more, and on the few I looked at, cover a handful of models per spring.

    If you want to know which stihl model use a particular spring, I can print it out.
     

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