Hogging Out the Exhaust Port
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Thread: Hogging Out the Exhaust Port

  1. #1
    Senior Member elime's Avatar
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    Hogging Out the Exhaust Port

    I figured I would leave the "Performance Cam" thread and start one dedicated to opening the exhaust passage on the TW head.

    Having gone as far as I could on the first head because the studs on the exhaust port got in the way of my die grinder I decided to move on and violate my other spare head. (Actually when I first got it I cleaned it and lapped the valves and got it ready for the day I needed it. At that time I opened the exhaust port a little bit and it is evident in the pictures. Technically started the modification a long time ago.)

    In the first picture you see the exhaust gasket sitting a kilter on the end of the exhaust pipe.

    In the second picture I placed the gasket squarely on the end of the exhaust pipe and you can see the inside diameter of the gasket matches the inside diameter of the end of the pipe.

    In the third picture I placed the gasket in the exhaust port of the head and you can easily see the inside diameter of the gasket is much larger than the diameter of the hole the exhaust gases exit through. It seems to me that this can be improved upon! So with no studs in the way and lessons learned on porting the first head I will charge forward and see what I can do on the second and last spare cylinder head I have.

    PA280049 (2).JPG
    Heli-Mech, Tweaker, Mel and 11 others like this.
    Long live the internal combustion engine!

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    Senior Member scotti158's Avatar
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    Bigger port doesn't necessarily mean better, but if you have an extra head, it's worth a try. Dyno before and after would be really informative, but probably not practical.
    2013 Yamaha TW200

    1996 Yamaha TW200

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    2002 Yamaha RoadStar 1600 with sidecar

  3. #3
    Ken
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    Senior Member Ken's Avatar
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    Are you going to put bigger valves in it?
    Cornelis likes this.

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  5. #4
    Senior Member elime's Avatar
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    Quote Originally Posted by scotti158 View Post
    . Dyno before and after would be really informative, but probably not practical.
    No money in the budget for dyno tests.

    Quote Originally Posted by Ken View Post
    Are you going to put bigger valves in it?
    I am sticking with the stock valve. Hopefully this will become a project anyone can do at home for very little $$$$$ and get an improvement in performance.
    Ken, JerseyJeeper, admiral and 2 others like this.
    Long live the internal combustion engine!

  6. #5
    Senior Member troll's Avatar
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    I've always believed that letting an engine breathe full always helps. Head porting both in and out can only improve things, imo
    elime and PlacerLode like this.
    Converte gladium tuum in locum suum. Omnes enim, qui acceperint gladium, gladio peribunt. - JC

  7. #6
    Senior Member scotti158's Avatar
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    Here is some interesting reading.https://en.wikipedia.org/wiki/Cylinder_head_porting
    troll and Peterb like this.
    2013 Yamaha TW200

    1996 Yamaha TW200

    1995 Kawasaki KLR650

    2002 Yamaha RoadStar 1600 with sidecar

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    Senior Member PlacerLode's Avatar
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    my mentor and buddy back in the day spent countless hours porting and polishing go kart motors but it really helped besides he was 6'6" tall and 80 lbs heavier than the other drivers and he won when the motor didn't grenade lol
    Cornelis likes this.
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  9. #8
    Senior Member elime's Avatar
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    It still needs to be cleaned up but I am done for today.

    Before:
    PA280050.JPG

    After:
    PA300049.JPG
    Mel, JerseyJeeper, admiral and 1 others like this.
    Long live the internal combustion engine!

  10. #9
    Super Moderator JerseyJeeper's Avatar
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    Looking good Tony!
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  11. #10
    Senior Member Peterb's Avatar
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    I always think about building "The Worlds fastest TW200". Lighten it up as much as possible, slam it to the ground, cafe bars, mod the engine to the max, gear it to the moon, 203/204s inflated to 100 psi. Sounds to fast for anywhere in Canada... road trip to Bonneville :-) I'll never get to sleep now.
    elime, Dryden-Tdub, troll and 4 others like this.

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