Sun Crusher 'Fat Wheel' 7-speed motorized?

Discussion in 'Photos & Bicycle Builds' started by KCvale, Jun 13, 2014.

  1. KCvale

    KCvale Motorized Bicycle Vendor

    If you ever venture to a real bike shop it is amazing what you can find when you do a lot of business there and the owner starts stocking things you might want to buy because they understand what you do with them.

    Try Me Bicycles around the corner got me today.
    They had a Sun Fat Tire bike for months, still do I think, but the old models had a suckey 2-speed kick-back rear hub and no hand brakes.

    Today when we went shopping for just a couple little parts and maybe a mountain bike to put the electric kit I have on, we spotted it...

    A Sun 'fat tire' bike with front and rear V-brakes, and a simple 7-speed twist rear!

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    Ya, $584 out the door for the bike, but with the proper engine and drive train it can be one heck of an off road (beach like) or city riding bike, and though I'm sure there are some examples before this Crusher design, this one might be pretty cool once I decade on what power plant and drive to use.

    I have every power plant type and drive parts sitting right here.
    I'll look, fit, play with math, then I'll decide what system best fits this particularly fun looking thing to motorize.

    Don't you just frigg'n love it when you can do stuff like this?
    I sure do ;-}
     

  2. KCvale

    KCvale Motorized Bicycle Vendor

    Just for some reference here it is parked next to the Electric 9-speed shifting Specialized mountain bike with with 2" tires.

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    I have decided on a 66cc jackshaft with an expansion chamber to move it along.
     
  3. LR Jerry

    LR Jerry Well-Known Member

    KC how wide are the tires? With tires that size it really reduces the need for a suspension system.
     
  4. butre

    butre Well-Known Member

    front suspension is nice to have for reasons other than ride comfort. a good suspension setup will keep your wheels on the ground over dips and after bumps.
     
  5. LR Jerry

    LR Jerry Well-Known Member

    I have front and seat post suspensions. Just saying those big tires are going to make riding that bike really comfortable.
     
  6. KCvale

    KCvale Motorized Bicycle Vendor

    The sidewall says 3.5" wide 26" tires but my caliper says 4" at their widest point, and inflation from 8 to 35 pounds so ya, they are like riding on balloons at about 20# hehehe ;-}

    That electric bike it is next however has nice front and rear suspension and does make a world of difference, we don't bat an eye at speed bumps.
     
  7. wheelbender6

    wheelbender6 Well-Known Member

    Looks like a great bike for riding in the sand in Havasu and the snow up on the rim.
     
  8. KCvale

    KCvale Motorized Bicycle Vendor

    Yep, or the Yuma sand dunes or around Tempe town lake.
    Engines here, 2-stroke sick bikes shift kit and expansion chamber exhaust are on their way.
     
  9. KCvale

    KCvale Motorized Bicycle Vendor

    Making progress.
    Got the 66cc Skyhawk with SBP shift kit and expansion chamber in.

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    I had to build the freewheel pedal sprockets backwards for the drive gear to reach but she works.
    Going to loose first and maybe second gear to avoid chain cross but this flys off the line in 3rd anyway and in 7th, well, lets just say it'll go faster than I care to ride ;-}
     
  10. KCvale

    KCvale Motorized Bicycle Vendor

    Update time.

    This is turning out rather well I think...

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    I am not to the cable and wiring yet, obviously, but the custom expansion chamber exhaust pipe went in sweet in my eyes.

    All steel parts hard welded and then coated with 4 coats of silver high temp engine paint and left outside to bake in the AZ sun and cool down overnight.

    I had to sacrifice some high end power reducing the length of the pipe, but it is where it simply has to be to function AND look good on this bike.
    Yes it has a lower mount as well, you just can't see it ;-}

    And can you believe I found the perfect chain guard for it in my fender box of them?
    The original was way too small but that one from an Electra I think with just a couple of 'snip snips' for the drive chain went right on!

    I still need to fashion a cover for the JS sprocket but we have done that before, it's just rare that I can get a pedal side chain guard that actually fits right on a shifter.

    The dilemma now after a bunch of riding miles is how to either lock out any gear below 3rd on the derailleur, or just put a new sprocket set on that sticks out far enough.

    I had to build the JS chainring backwards, meaning the drive sprocket is on the inside just to retain the width to clear the wheel but the chains cross below 3rd.

    As with anything like this on my own dime it takes back seat to a buying customers build so it may be a couple of days before I 'button it up', but then again I am unpredictable when it comes to things like this ;-}
     
  11. KCvale

    KCvale Motorized Bicycle Vendor

    Stick a fork in the beast, he's done.​


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    5 cables and the kill button wire from the handlebars but he buttoned up nice I think.

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    This is like a Monster Truck motorized bicycle for adults only.
    It is big and heavy but with all the 66cc Skyhawk engine mods and SBP shift kit it has all the power it needs and a frigg'n joy to ride with just 18# of air in those big fat tires.

    I'd like to keep it because it's soo cool and fun to ride but I have a much more expense 'box of parts' to build to ride next.
     
  12. KCvale

    KCvale Motorized Bicycle Vendor

    My big (6' 220#) mechanic / best friend absolutely loves this bike.

    He took it out for over 2 hours test riding it yesterday and snapped a few pictures of where he rode it which was up a pretty steep local trail with dirt/gravel/shale under him...

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    And then he hit the park...

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    Note that those fat tires didn't even leave a mark on the grass.
    You could ride this thing on a golf course and not do any damage, but it's not very practical as a golf cart ;-}

    I don't have easy access to sand but I'd bet he floats right over that as well.
    All in all a really fun bike if you put enough power in it.
     
  13. KeepOnKeepnOn

    KeepOnKeepnOn New Member

    Great job. It's very hard to make that many cables, CDI, jackshaft, etc look clean.
     
  14. KCvale

    KCvale Motorized Bicycle Vendor

    Thanks.
    I lucked out finding a chain guard that worked with the dual front sprocket as the stock one was way too small.
     
  15. hellbound212

    hellbound212 New Member

  16. KCvale

    KCvale Motorized Bicycle Vendor

    Got a back flat.
    The tubes are cheap ($13) but those tires have a steel belt on the lips and tough to get off and on, but that's what you need when you want to run just 10 pounds of air.
     
  17. Jay Andre

    Jay Andre New Member

    Want to motorize a Sun Baja Cruz, formerly called Crusher, just like the one pictured

    Dear KC, and everyone. The 1st question I have b4 proceeding any further with this form, and/or the purchase of the bike is...is the frame on that bike actually chrome plated, or painted silver, and the company calls it chrome in their description of it? That's all I need to know, for starters. Thanks.
     
  18. schwinn123

    schwinn123 Member

    This beast is perfect. Great build.
     
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