Ecarpat Fat Tire Bike

[duke]

I am getting together components to build motor bike with 80cc Skyhawk with Gru Bee Jack shaft kit.
Other than the 3” back tire spacing from down tube not quite sure on the 28 or 32 kit with respect to down tube diameter?
Like to purchase the Jack shaft & motor now, while available
Anyone do a fat bike build using the Gru Bee Jack shaft?
Any input greatly appreciated

 

[Sidewinder Jerry]

Over the years several have built fat-tire shifter bikes. The biggest issue most face is fitting the components into very limited spacing.

 

[Venice Motor Bikes]

The seller has the wrong term written for the 'downtube'... they mean to say 'seat post tube'!!!
(The downtube is the tube that runs from the fork down to the crank bracket).

To answer your question... go buy a cheap caliper & measure your seat post tube... that will tell you if you need a 28 or 32.

 

[duke]

Typically a 28 is a steel frame and a 32 is aluminum. The GruBee Jack Shaft Kit is designed for a Micargi Slugo, requires more forward stance in the frame.
There is a Jack shaft kit that will fit Mongoose Dolomite or the Ecarpat readily available
SickBikeParts gone so
Either I find a Macargi Slugo or a clone, the GruBee is dead in the water.
I like GruBee they have been going back & forth trying to help. I can literally go around looking at fat bikes with tape measure in hand, wouldn’t be the first time! Once I get a vision I’m driven to prove it can be so

 

[Sidewinder Jerry]

Typically a 28 is a steel frame and a 32 is aluminum. The GruBee Jack Shaft Kit is designed for a Micargi Slugo, requires more forward stance in the frame.
There is a Jack shaft kit that will fit Mongoose Dolomite or the Ecarpat readily available
SickBikeParts gone so
Either I find a Macargi Slugo or a clone, the GruBee is dead in the water.
I like GruBee they have been going back & forth trying to help. I can literally go around looking at fat bikes with tape measure in hand, wouldn’t be the first time! Once I get a vision I’m driven to prove it can be so

My shifter bike is the Sidewinder. This is my second shifter bike. The first one I had was the LandRider which shifted 7 gears automatically. Many told me what I was wanting to build was impossible and couldn't be done. I rode the bike for 10 years. LandRider went out of business and I knew if I ever needed replacement parts they'd eventually become hard to find. This is the reason I retired the LandRider and built the Sidewinder. So I admire you for having drive and determination.

 

[duke]

Yeah, if I listened to all these doubters nothing would get done
Should see some of my custom tractors that couldn't be built.
The Sidewinder. Have a picture?
I looked at a Granite Roadmaster, about the same bike, 50 bucks locally.
The fat tire bike is my challenge, although the Roadmaster was very tempting-$
What is your source for the parts? Motor, shift kit etc.
Did you use a thumb shifter?
Can an electric start 80cc engine work with the drive shaft kit or is the starter right in the way?
Lastly 2 stroke right, as a four stroke set up won't work on the drive shaft kit will it?
Be nice to have the centrifugal clutch tho'
Here's a Mongoose Dolomite I seen earlier today but can't find the post now
!

You decide to help with a source or two that would be cool

 

[Sidewinder Jerry]

I use a 4-stroke Robin Subaru EH035 engine. I have a triple chainring shift kit. I use 2 Sram trigger shifters mounted on the left handlebar.

I invented a color-coded one-hand shifting system. With this system, the bicycle chain stays in a fairly straight line with no cross-chaining. I only shift a front chainring when in either rear sprockets (3) or (5). The 3 colors are for different riding scenarios. So the majority of the time I'm only shifting 3 gears. My starting gears are 1(1) for starts going up hill and all other starts are 2(3).

My max hp rpm is at 7000 rpm. I use a tachometer to shift by. This way at full throttle I'm always in a gear where I'm at max hp rpm. Thus increasing my average speed in hill country.

 

[duke]

Really well done! Complex, no one gonna hop on and drive away with that system! I wasn’t aware of the triple chain ring option, nor how the application would go together.
I built my first MB almost 15yrs ago and that was pretty cool, some tweaking but non too difficult.
Problem being all the changes in components, how they fit & function in a system they are not really designed to withstand for very long without constant maintenance
Buying engines now a days! China Doll’s are ok but the clutch thing is odd. I’m leaning towards 4stroke as well, but where to buy a decent kit? Can a Jack shaft be used with a 4 stroke per se? Like a 4” wheel I’d need to be able an reach out to go outside the girth of the tire.
Perhaps you are more familiar with this I’m sure you are more familiar!

 

[Sidewinder Jerry]

The late KC Vale did several 4 stroke shifter builds, here's a few of them. He even built a fat-tire electric shifter.