Sun Crusher 'Fat Wheel' 7-speed motorized?

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!

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 ;-}

 

[KCvale]

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

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

 

[Sidewinder Jerry]

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

 

[butre]

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.

 

[Sidewinder Jerry]

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

 

[KCvale]

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.

 

[wheelbender6]

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

 

[KCvale]

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

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.

 

[KCvale]

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

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 ;-}

 

[KCvale]

Update time.

This is turning out rather well I think...

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 ;-}