Specialized BIG HIT MTB build

Discussion in 'Photos & Bicycle Builds' started by ToyTruck, Apr 3, 2013.

  1. ToyTruck

    ToyTruck Member

    This bike is one I was just using as a sort of daily ride.
    Even though it had the energy sapping Full Suspension , it was fun to ride.

    Then the motored bike bug bit and it was a challenge to fit a motor to the Big Hit frame.


    Assuming a rack mount would be my best option , I looked into it and the best solution I could find was to fit the motor BACKWARDS ... Changing the timing and fitting the rear sprocket in behind the rear gear cassette.

    After a bit of work building a frame to bolt the motor to the rear section of the bike.


    The motor had a few issues straight out with a bearing failing.
    No real big issue , but having the motor apart sucked me right in to modding it for more power / torque.
    Fitted a RSE Reed Valve
    Fitted a CNS carby
    Drilled the piston for the reed valve as well as grinding transfer ramps and trimming the skirt

    I looked at correcting the transfer ports but they seemed to be a lot better than some of the pics I have seen.

    The only thing I haven't done yet is adding the boost port and haven't looked at high Comp head.

    The bike was fun , even with the standard exhaust.
    But the weight hanging off the back of the bike was slowly starting to annoy me.
    Then for no real reason , the bike started throwing the chain on heavy hits .... Landing a small jump or dropping of a road kerb was enough to throw the chain.
    Possibly just the crappy chain, but there was a bit of flex from the rear frame of the bike.

    So that brought me to start phase 2 .....
    I love the bike too much to just start with something else so I looked at it and decided to remove the rear suspension and , in place of the rear strut , fit the motor.


    Seems like a good idea !!!!
    Anyway , I am halfway thru this phase of the build , the bike is now front suspension only. And it rides sooooo much better.
    I am sure I will miss the rear suspension , but I am not too bothered for now.
    The frame I built uses the mounting points from the suspension strut and pivot point, so it can all be put back to original if needed.

    Here it is , still needs fuel tank and carby
    And also needs a Jaguar torque exhaust built

    That's it as it is now ,
    66/80 cc motor
    RSE Reed Valve
    CNS Carby
    Piston ported

    Hope you like,

  2. professor

    professor Active Member

    Pretty cool. I like it.
  3. ToyTruck

    ToyTruck Member


    The bike rides so much better with the weight balance
    I hardly know the motor is there , where as before , I could feel the weight all the time.
    The rear weight would some times feel like there was a child in a bike seat on the back throwing I tantrum lol
  4. geebt48cc

    geebt48cc Member

    Awwwwwwwwwwwwww, Toy, maybe there's hope for this GMC TOPKICK I've got????????????????

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