sbp expansion

Discussion in 'Motorized Bicycle General Discussion' started by kyl 46&2, May 19, 2010.

  1. kyl 46&2

    kyl 46&2 New Member

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    i just put on a sbp expansion chamber yesterday, although it fits its a tight fit and i'd like it a little more secure. i messed around with adjusting it for 2 hours trying to get the best fit but its not quite where i would like it. i want to know if its ok to take off about an inch on the J pipe and how it will potentially effect performance on a 80cc. this is all on a 29'' mountain bike with a few other mods.
     
  2. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    Go ahead & cut the pipe! I once cut several inches from the J pipe & it still worked great!
     
  3. taddthewadd

    taddthewadd New Member

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    Like venice says go for it. I emailed the same question to SBP and they said it is ok but it will take away a little bottom end torque and give you a little more top end power.
     
  4. N8dogg

    N8dogg New Member

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    I just put one on a over the weekend and had to cut a couple inches off also. Ive had to mod just about everything I have put on my bike so far. Im only at 100 miles on my kit but i was only topping at 25-26 and am now hitting 29-30. Seems like no performance issues for me. and plus it sure sounds sick
     
  5. BarelyAWake

    BarelyAWake New Member

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    Modify a SBP expansion chamber exhaust?!?! Mebbe :oops:

    [​IMG]

    A "coupla inches" is totally within acceptable range - you'd not wanna go longer than mine or any less than say six inches for best performance. Like taddthewadd mentioned, if you've got the room & fit to spare - the length can be adjusted to fine tune the powerband to suit... but it's not a profound enough difference to sacrifice it's mount and fit - even style/look if that's a priority.
     
  6. kyl 46&2

    kyl 46&2 New Member

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    i took off 1'' and it made a perfect fit. then today i went out to test it and busted the threaded rod on the motor mount for the down tube. its totally recessed in the motor. i'm kinda at a loss here. it really sucks i stayed up till 3am tinkering around getting everything just right and now this. i was thinking about using an easy out bit but not sure if it will work. has this ever happened to anyone else and any suggestions
     
  7. Saddletramp1200

    Saddletramp1200 Custom MB Buiilder

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    BarelyAwake, Wow. A work of art.Bravo! (c)
     
  8. BarelyAWake

    BarelyAWake New Member

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    Thanks Saddletramp :D Thats a stock (port-matched ofc) headpipe w/a lil bit of the SBP headpipe welded on as an OD to ID adapter (still clamped at the next junction to help w/removal) and an extended glasspack silencer made out of a chunk of 2" OD aluminum conduit BTW, easy-peasy ifn anyone's lookin' for a quieter ride w/o sacrificing performance.



    kyl - If it's even a lil bit close to the surface, by far the easiest way is to place a small nut over the hole and do a tiny plug weld w/a mig - basically turning a stud into a bolt, it's the easiest way to extract if you've enough to work with.

    If it's too deep - then yea, the "easy outs" are your only option, except if you get a left-handed drill bit (cuts counter-clockwise) to drill the hole for an EZ out instead of a regular bit - sometimes the drill bit itself will back out the broken stud and you'll not need the EZ out at all... *crosses fingers*

    If all that fails and the hole ends up oversized it's still ok if you were careful - there's enough meat to tap one size larger, even helicoil if you're picky and wanna keep the stock stud size.

    I hope it works out easy for ya :)
     
    #8 BarelyAWake, May 20, 2010
    Last edited: May 20, 2010
  9. kyl 46&2

    kyl 46&2 New Member

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    thanks for the advice. i'll give it a shot as soon as i can. just got done reading a thread on all this. i put rubber under the mount a couple days ago. turns out that was a bad idea. unfortunetly it is flush with the motor so i will have to go the EZ out way.
     
  10. BarelyAWake

    BarelyAWake New Member

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    If it's flush - then the weld trick will prolly work as the weld (steel) won't adhere to the aluminum and the welding is so short a duration that the heat wont damage the aluminum (careful ofc), as you just need fill in the nut...

    But - w/e will work, I just don't like EZ outs very much lol - too bad there's no alternative sometimes :(
     
  11. Mac

    Mac New Member

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    KYL46,
    I stopped counting the studs Iv'e broken, I think I've become an "extraction" specialist.LOL, As Barely said, a left handed drill bit, you can get a kit at sears, left handed drill on one side, flip the bit in the drill, easyout on the other. If the stud is flush, try cutting a slot in the stud and use a good screwdriver to thy to screw it out, you will cut the cas a bit, JB weld fills nicely. When you put the new better quality stud in, spray it with a lube, no Loctite on the case side, screrw it in loosly, I don't wrench it in, this will facilitate easier removal if it breaks again. Make sure your engine sits "in the saddle and thet the mount bolts are not pulling the engine to the frame. Hope that helps.

    Mac
     
  12. kyl 46&2

    kyl 46&2 New Member

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    got the bugger! had to dremmel a slice into it, lube it up with some PB then it came out nice and smooth. i'll pick up some new threaded rod tomorrow and put it all back together hopefully it won't rain and i'll get to ride. thanks for all the help guys
     
  13. BarelyAWake

    BarelyAWake New Member

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    w00t! dance1

    Good ta hear kyl, ride on!
     

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