Expansion chamber

Discussion in 'Spare Parts, Tools & Product Developement' started by biken stins, Mar 10, 2009.

  1. biken stins

    biken stins Member

    Has anyone tried or know about the Sky Hawk expansion chamber ?
    Saw them on Spooky Tooth in their engine section. The STC site lacks on details and size engine it is to be used on.


    TINKERER Member

    I've been curious too, $50 might be worth it!

    TINKERER Member

    So I just bought one, I will do a review soon!

    TINKERER Member

  5. spad4me

    spad4me Member

    I just insalled an expansion chamber on my happy time.
    Mine needed welding,

    Nasty twisty bends,in relatively small pipe.
    A lot of trial and error.
    a jet modification.
    Lower restriction air filter.
    I would say at least a 30 percent improvement.

    A bolt on expansion chamber sounds a lot easier.

    I haven't port matched mine yet.

    TINKERER Member

    I got the Skyhawk pipe today from Spooky Tooth, super fast shipping, only three days! the pipe looks great and came with a nice gasket, I bolted it on and it fit perfect except when I pedaled, very bottom of the crank arm just barely ticked the pipe, I'll grind off an 1/8" from the end of the crank. anyway, I took it out for a spin WOW!!! It was noisy, pop...pop...pop.. like a tuned pipe should sound, I went for a 3 mile ride and decided it does definitly increase performance, the power band is in the higher rpms, But I cant handle the noise, actually I love the sound! but it drew alot of attention, (I live downtown Minneapolis) so I dont think this pipe is for me I want to be stealthy when I ride and stay out of trouble. :icon_cry::icon_cry:
  7. biken stins

    biken stins Member

    Sounds good. Ordered Thur. Did ask Roland if you could put a silencer on it. It would have to be DIY. There are some on scooter sites but someone with more knowledge would have to point the direction. I like some of the one that others have made on this site.
    Did you get the carb also ?

    TINKERER Member

    I do want the CNS carb, also next engine I buy I will have STC do all of the port work, polishing and milling, for $75 thats not bad at all.
  9. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member


    TINKERER Member

    That's strange, The pipe is no longer listed on the STC site, STINS and I must have ordered the only two they had? I will get some pics of it for you.
  11. biken stins

    biken stins Member

    See they do not have it listed now.
    It could use some refineing but is a starting place.
    Like Tinkerer said the pipe hit the crank.
    Solution was raising engine a tad.
    The carb also may not fit all bikes and engine raised. That is due to the cone air filter. A motor mount and studs are included.
    Give roland a call. Very helpful.
    Did talk about the noise. A pipe could be ran back into a silencer.
    Where it bolts to engine is the same small round hole as other exhausts on the engines.
    Looks like if it was made bigger could cause a problem from becoming weak. A new extended flange and hole reamed out to fit port chamber seems like it would help a lot. It would also make so no tweeking of the crank is needed. A good clamp is needed on it to be on the safe side.
    Seems a good starting point for some extra power and wee bit o speed.

    TINKERER Member

    This morning I got creative thoughts and went to ACE to see if I could piece together some sort of silencer, Here is what I found

    Ace small muffler part # 72663 I painted it to match my bike.
    copper 1/2" I.D. threaded fitting that reduces to 1/2" O.D. the big side screws onto the muffler with some force.
    Stainless Hose clamp.
    I cut four 1/4" slots in the 1/2" reduced side and slid it over the outlet of the tuned pipe, and used a hose clamp to squeeze the reduced side to the pipe,
    The silencer does work some but is still not "stealthy" but the increase in overall performance with the tuned pipe and silencer makes me happy.
    here is a pic:
  13. jlebh1

    jlebh1 Member

    very nice pipe wish we could get them here in australia but a couple of the guys who sell the grubee engine are looking in to ordering them