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Fist time porting question (372)

Discussion in 'Chainsaw' started by Ronie, Feb 13, 2019.

  1. Ronie

    Ronie ArboristSite Operative

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    I'm going to try and make this as short as possible. I thought I'd try porting a 372 Farmertec cylinder before I try it on an OEM cylinder, so I got my pencil grinder out and widen the exhaust and intake 1mm. I matched the cylinder to a crankcase and knife edged the lower transfer dividers. I looked a little ruff which was ok because this was just to get the feel for grinding. So, I rebuilt a 372 this week and decided to put this ported cylinder and a pop up piston on the saw to see how it would run. It didn't run bad but I couldn't get the rpm above 12900. I tried two 385 carbs and a 372 Walboro with the same result. I didn't put a degree wheel on it so I don't have any numbers. The question is, what controls how high a saw will rev? Any help would be appreciated.

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  2. mkinslow

    mkinslow ArboristSite Operative

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    What is your carb settings at? Unless I missed it i didn't hear it 4stroking when you were reving out of the cut. Still seems fat to me.

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  3. Ronie

    Ronie ArboristSite Operative

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    I started at 1 turn out but tried leaning it out and giving it more fuel with all the carbs, max rpm was 12,900 You might not hear it in the video but it's for stroking. I pulled that top end off and put another on and you could tell it was running rich, very wet.
     
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  4. mkinslow

    mkinslow ArboristSite Operative

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    Blue or black coil ?

    Sent from my SM-G892A using Tapatalk
     
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  5. Ronie

    Ronie ArboristSite Operative

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    Could the compression have anything to do with it? I didn't put a gauge on it but it was very high.
     
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  6. Ronie

    Ronie ArboristSite Operative

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    Black
     
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  7. mkinslow

    mkinslow ArboristSite Operative

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    Black is unlimited. So that shouldn't be holding it back.

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  8. mkinslow

    mkinslow ArboristSite Operative

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    I wouldn't think so. Usually if too low they want hardly start. Really high and itll RIP your fingers off.

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  9. Ronie

    Ronie ArboristSite Operative

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    It was the rip your fingers off kind of compression. Maybe it wasn't getting complete combustion, it was very wet inside.
     
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  10. mkinslow

    mkinslow ArboristSite Operative

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    Try a different plug. Also when I ported my husky 365 it required more fuel than it did when stock. So it's out almost 2 turns on high side and 1 1/2 on low side.

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  11. Ronie

    Ronie ArboristSite Operative

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    I took that top end off and put another one on it. I was curious about what could cause that.
     
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  12. mkinslow

    mkinslow ArboristSite Operative

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    I'll think on this some more. Hopefully someone with more knowledge will chime in shortly.

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  13. Ronie

    Ronie ArboristSite Operative

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    Ok, thanks for trying.
     
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  14. Ronie

    Ronie ArboristSite Operative

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    I think I'll put that top end on a crank case and get some numbers. Maybe that will shed some light on the reason why.
     
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  15. Westboastfaller

    Westboastfaller Addicted to ArboristSite

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    + 1 for the plug.

    3 diff carbs you say.

    Is that an AM black coil?
    I can't see vids so I can't hear i, just to let you know. Porting looks mild. Not sure about exhaust though. can't see inside.
    Really doubt from what I see it's porting.
     
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  16. Ronie

    Ronie ArboristSite Operative

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    It's not the plug, I used the same one with the new top end. It is an AM coil but it works fine with the new top end.
     
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  17. Westboastfaller

    Westboastfaller Addicted to ArboristSite

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    slow down a bit maybe? Just a thought.
     
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  18. Ronie

    Ronie ArboristSite Operative

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    I've already put a different top end on that saw.
     
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  19. mkinslow

    mkinslow ArboristSite Operative

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    I've seen different plugs act funny in high compression areas. Its worth a try. And maybe a different coil OEM if you have one.

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  20. Westboastfaller

    Westboastfaller Addicted to ArboristSite

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    Top end with same piston you mean?
    Stock piston skirt length?
     
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