11% PRICE REDUCTION! Seat Post Jackshaft Bracket for 4" Fat tire bike.

Grubee Inc


PRICE REDUCED:   WAS $180 / now $160.


This Seat Post Jackshaft Bracket is for a mounting a 2 stroke China Doll engine inline Mid-frame on a Micargi Slugo 4" single speed Fat Tire 26" Cruiser Bike.    THEREFORE, THE ENGINE IS NOT Offset! 

Don't have a Micargi Slugo Bike?  No problem, we can sell you one dropped shipped from MiCargi Calif. warehouse.  

Our SeatPost Jackshaft fits a 28mm dia. steel seat post that is 3" away from the 4" rear tire.    Yes, may fit other steel framed bikes too with same dimensions?   

We 100% guarantee to fit the 26" Micargi Slugo 4" tire bike frame!

  • FYI:  We will only make 35 of these CNC SEATPOST JACKSHAFT KITS to test the market.  

Made in USA   Means highest quality workmanship!  Maybe we will make these Seatpost Jackshafts in the future in China but not certain if and when.

First time offered:     

  • USA Machine shop made.   Repeat  > NOT MADE IN CHINA.                      Made in Oklahoma by me and the 7D CNC machine shop in Boswell OK!  

  • Especially designed for Micargi Slugo 26" 4" tire bikes that have 3" clearance between seat post and tire.  However, may fit other brand bikes but must have the said 3" tire clearance and 28 to 28.5mm dia. steel seatpost. 

  • To avoid a return for non-fit measure your bike before buying.

  • NOTE:  4" tire Slugo Bikes can be ordered from us and yes, they have the required 3" clearance and 28mm dia. seat post. 

  • By using our CNC solid billet jackshaft bracket the 2-stroke engine remains in the middle frame position same as would be in a standard 2"-inch tire bike thus giving best balance and professional look.   Problem solved!

  • Up until now the only way to have an engine on a 4" tire bike was to offset it to the left or use a Sick Bike Parts jackshaft to the right-side pedal sprocket.  Unfortunately SickBike parts went "out of business".  Problem Solved!

  • The GruBee Seatpost Jackshaft Bracket allows the engine drive chain to drive an inboard 9T sprocket and the outboard 10T sprocket allows chain clearance to go on past the 4" tire and drive the rear wheel.   Problem solved

  • The problem of how to tighten the engine chain to the inboard sprocket is solved by our Non-concentric Cam Lock Hub, same idea as used in our 4G 4 cycle transmission.  Problem solved!

  • Heads up:  At first, we were going to supply a CNC spacer block and longer M8 Studs that pushes the engine forward to the bike's downtube but found out that an additional engine mounting blocks and (2) 8Mx110 studs can work much cheaper than a solid billet CNC block.  You may have to extend the threads on one end of each M8-1.25 stud out to 40mm thread length to allow clasp to fit. Problem solved!

  • BOM:   

  • 1.  2 pcs. Seat post mounting bracket and hardware. 

  • 2.  Cam lock cylinder and hardware   

  • 3.  Stainless Steel Shaft and (2) 5x5x20 keys. 

  • 4.  (2) 10T & 9T sprockets with set screws.

  • 5.  (3) 15mm ID Spacer washers.   

  • 6.  Dual spacer blocks and (2) M8-1.25x100 threaded studs. 

  • Customer must make their own sheet metal chain guard and obtain the required 415 drive chain.   ( Chain and chain guard are Not Included. )

  • Due to high cost $125 / hour CNC SHOP USA labor rate we will only make 35 of these Beautiful CNC SEATPOST JACKSHAFT KITS to test the market before taking the project to Riceland.   

  • If you want to right hand drive down to the pedal sprocket with a smaller inboard sprocket with freewheel driving a 1/2x3/32" chain Multi Speed rear axle let us know.  N/A at this time but we may decide to have some made in the future.   A Jackshaft right-hand drive multi-speed should take speed enthusiasm into fear with the torque of 79cc 4 stroke unleased without any governor control.