4 Cycle Stage1.5
www.grubeeinc.com         www.chinabestexporter.com

with 2hp. 4 cycle Honda GXH 50-50cc,  or  HuaSheng F142 49cc engines:
( Consult your Skyhawk dealer for correct model HuaSheng engine to use: )

Power control system with Gru-Bee centrifugal clutch gear box with an in > & < out engager

Kits available with 49cc HuaSheng F142 engine or without engine for use with Honda GXH50 engines;


Universal Kit

142FL-AG engine
For mountain bikes with dual suspension or regular bikes;  
18” wheels to 26”

< Gru-Bee Power control gear box with shift lever engagement for safe operation;>
Engine gear box ratio: 4.2 to one,
Final drive ratio with 11T primary drive and 56T rear sprocket is 9.29 to one engine rpm.
Output drive sprocket has a freewheel to allow no restriction when pedaling engine off and can also help prevent rider injury in case of sudden engine lock up failure.

< Aluminum Castings machined on CNC machines for  precision and quite running>

USA patent pending: 11428539-4173      Mechanical aptitude and basic tools required.

Donor bike specs. for Vee frame mount;   > The motorcycle look:

 24” to 26” cruiser bikes with a 30 to 38mm dia. front down tube and 28mm dia. seat tube works best as a donor bike.   Large bottom hole, approx. 52mm dia. ID needed to accept a one piece pedal crank.  Works with standard spoke clamp chain wheel sprockets or with the recommended HD axle kit.    It is essential that donor bike have both front and rear brakes for safe operation.

Folding bike with rear engine;  > MoPed using 142Fl-AG HuaSheng engine with special carb.

Hybrid;   Electric / Gas & Pedal;  > ElMoPed; using 142Fl-AG HuaSheng engine special carb.

Donor bike specs. for over the rear wheel mount;  > fits 80% to 90%  of all bikes:

Universal kit for all bikes;  Can be made to work on most all adult bikes including mountain bikes with dual suspension or standard rigid frame men’s or lady’s bikes or even the new style small 20” to 18” folding bikes as well as recumbent bikes:    Wheel drive sprockets available from 56T to 44T.  No wide pedal crank or tear drop gas tank necessary.  Works with standard spoke clamp chain wheel sprockets or with the recommended HD axle kit.    Donor bike must have both front and rear brakes for safe operation.


Always were a safety helmet when riding a motorized bike and abide by local and state ordinances.


Disclaimer;    End user or installer becomes the vehicle manufacture and assumes all laws of the land
                     including product liability and correctness of installation.  End user assumes all risk and
                    obligations for safe use;    Do not purchase or use this product if you expect otherwise.

Model #1 HD axle kit: 26” bikes can use 56T rear sprocket for use with standard 11T freewheel primary drive or 50T for use with optional 10T solid primary drive sprocket kit sold in service parts:

More safe operation than with standard clamp to spoke sprocket attachment.
Freewheel sprocket hub allows easy pedaling with engine off. 
Hub flange sprocket attach ensures true alignment and no broken spokes.
Drum brake included optional:

Model #1 Available with 44,  50 & 56 T sprockets:   Opt. 3 piece wide pedal sprocket:


Engine Applications:

REAR ENGINE MT.  >  Use 142FL-AG HuaSheng for rear engine mounting with  gas tank lower than carburetor:   Has special carburetor that can pull gas up from lower tank.    HONDA NOTE:  Can not use a Honda GXH 50 engine for rear mounting unless original above engine gas tank is also used.    Honda’s GXH50 engine carb. can not pull gas upward.   Check with your Honda dealer to see if a model is currently available with primer carb. to pull gas upward.   A gas tank on top of the engine makes for a very tall installation.

VEE FRAME ENGINE MT.  > Use 142F-G or 142F1-G HuaSheng for Vee frame engine mounting with gas tank mounted on bike frame top tube above carburetor:  HONDA NOTE:   To use a Honda GXH50 engine for Vee frame mt. use > GruBee /SkyHawk Honda vee frame installation kit.
HUASHENG 49cc Engines

DATA SHEET OHV Engines for China GAS
142FL-AG                                                      142F-G & 142F-1-G
142FL-AG                                                      142F-G & 142F-1-G
Descriptions Model 142FL-AG Model 142F-G Model 142F-1-G
Type 4 -stroke OHV 1 cyl 4 -stroke OHV 1 cyl 4 -stroke OHV 1 cyl
Eng. displacement 49cc 49cc 49cc
Output Shaft Rotation CCW CCW CCW
Bore  & Stroke 41.8 x 35.8mm 41.8 x 35.8 mm 41.8 x 35.8 mm
Max. Power   1.4KW/6800rpm 1.4 KW/ 6800 rpm 1.4KW/6800rpm
Max. Torque   2.0Nm/4500rpm 2.0 Nm / 4500 rpm 2.0 Nm / 4500 rpm
Max. rpm no load    7500rpm   7500rpm  7500rpm 
Output Shaft size   15.853 dia. x 33.5mm 15.853 dia. x 33.5mm *15.78 dia x 33.5mm   
Fuel consumption 480g / Kw Hour 480g / Kw Hour 480g / Kw Hour
Engine Cooling forced air forced air forced air
Ignition TCI TCI TCI
Engine size:  L x W x H         400*320*355 400*320*355 400*320*355
Net wt. without tank              5.7kg 5.7kg 5.7kg
Engine PTO rotation  CCW  CCW  CCW
Crankcase oil volume 0.25L 0.25L 0.25L
Eng. Compression ratio           7.4 7.4 7.4
Engine idle rpm  1800±150 1800±151 1800±152

Note;   Check engine mounting hole thread sizes carefully.   Some Honda and HuaSheng engines have ¼ -28 English treads and some have 6m x 1.0 metric threads.   If you engine has different size threads than the fasteners supplied in this installation kit obtain the correct size bolts at your local hardware store.

1.   Install wide pedal crank and pedal sprocket 2.  Mount bracket to engine; Check thread sizes:
3.     Install centrifugal clutch assembly: Step one;    Install key in engine shaft:
Step 2:  Slide clutch on shaft aligning key to slot: Step 3.   Slide gear bell housing on shaft:
Step 4.   Slide on inter race sleeve aligning key slot: Step 5.  Install washer and ¼ x 28 retaining screw:
Step 6.  Install gear box to engine with 2 short screws: Step 7.  tap middle gear in alignment;
Step 8.   Be sure spacer sleeve is on rear gear shaft: Step 9. 1mm tk. spacer washer next to middle gear:
Step 9.  Install gear box cover: Step 10. Install 2 long screws and one short one.
4.  Install muffler with studs in kit: 5.  Align engine to rear sprocket: 6. Tighten mounting brackets::

Note:    When installing the chain on the drive and wheel sprockets be sure to install the master link on the outboard side of the primary drive sprocket or it will hit the gear box if installed on the inboard side.
(  Severe engine damage can occur if the master link hits the gear box. )

Note: To remove gear box cover first pry with screw driver at rear then at front to work cover off gear box.


Standard Muffler  Long poo poo pipe;
Steam line fancy motorcycle type;
( Available in black or bright chrome finish. )
Modified stock muffler for rear mount;


[Part1]     The gear box power control system 1 consist of three major assemblies.   (a.) 2 piece Centrifugal clutch assembly.  (b.) Cast housing 10 with all working parts, 3 spur gears, 2 shafts and the engager system all factory pre-installed.   (c.) Cast housing 11 referred to as the cover housing having two ball bearings factory installed.

[Part2]     Installation and operation as used on a Bicycle:   The gear box power control system 1 is attached to the engine by two long mounting bolts going through four hole lugs 26 in the cast housings 11 and 10 and two shorter bolts inside the gear box on cast housing 10 going through holes 26 approximately midway of cast housing 10.  Obviously the two shorter bolts in cast housing 10 approximately midway must be affixed first to the engine before the cover cast housing 11 is installed.  Therefore, this makes a four bolt mounting for the gear box power control system 1.

[Part3]     When the engine is operating above a specified rpm usually about 2000rpm the centrifugal clutch 12 engages the clutch integral bell housing and transmits engine torque through a series of spur gears in a train from gear 13 to gear 15, from gear 15 to gear 17 on the same shaft, and from gear 17 to the final drive gear 19 to the output drive sprocket.

[Part4]     Installation step one:  Install centrifugal clutch assembly 12 and bell housing with primary drive gear 13 to the engine output crankshaft 14.  

[Part5]     Installation step two:   Attach cast housing 10 with gear train and integral engager assembly factory pre-installed to a vertical single cylinder Honda GXH 50 or HuaSheng F142 4 cycle engine as shown in FIG. 7.  Cast housing 10 is placed over the centrifugal clutch assembly 12 and primary drive gear 13 by way of a large hole in cast housing 10 and is first held on by two short bolts going through holes 26 approximately midway of the cast housing into two corresponding threaded holes 25 on the engine.  Lubricate gears with heavy grease before installing cover.
[Part6]     Installation step three:   Attach the cover housing 11 having two ball bearings that line up with corresponding shaft 16 & jackshaft 18 in the cast housing 10.   The cast housing 11 is then tapped into position with a rubber mallet to fit tightly over the cast housing 10 in a recessed lip around the perimeter.   After cast housing 11 is in position two long bolts are inserted through the two left side lug mount holes 26 of both the cast housings 10 and 11 as shown in Fig. 8 and also extended into the threaded holes of the engine accessory drive mounting flange 25.  A single third shorter bolt is installed through hole 26 on the right side of the cast housings 10 & 11 as shown in Fig. 8 and all three bolts tighten securely in sequence.   The shift lever 22 with steel cable 8 attached going to hand lever 9 are preinstalled at the factory for ease of installation on the bike handle bar.   The Bike wheel drive chain can now be installed as required.

[Part7]     Operation sequencing:     Gear train spur gears 15, 17 operate on shaft and bearings 16, and the final drive spur gear 19 operates on a jackshaft with bearings 18.  The gear train is used to transmit power in a step down speed ratio.   A ball bearing supported output jackshaft 18 having final drive spur gear 19 which can rotate freely on a bronze bushing.   The final drive spur gear 19 has a small fixed position engagement gear 20 welded to it in centerline position and transmits power to the sliding engagement gear 21.  The engagement gear 21 slides on a long key inserted in a key way on the jackshaft 18 as shown on FIG. 4.  The sliding engagement gear 21 is moved by a pivoted lever 22 controlled by an external cable 8 and hand lever 9.  The shift lever 22 is made with twin half circular shaped fork arms having hole slots at the end of each arm that fit on a full circle ring 32 with buttons 30 located on the sliding engagement gear 21 and held on by a flange 33 secured with threads or a lock ring.  as shown on Fig. 9A.  Thusly, the shift lever can push and pull the sliding engager gear 21 to engagement or disengagement position.   A similar concept is used to push and pull a starter drive for engine ring gear engagement in an automotive DC electric cranking motor.
[Part8]     The small primary drive sprocket 23 used on the engager assembly jackshaft output end has an over running freewheel clutch.   Thus allowing freewheel operation in one direction and lockup in the opposite direction.  The primary drive sprocket can be ten tooth, to eleven tooth as required by the driven wheel work application requirement and size of engine used.  The WD distributor has the option of ordering a freewheel primary drive sprocket 23 or a non freewheel primary drive sprocket on the output jackshaft 18.   If a non freewheel sprocket is used on the jackshaft 18 then a freewheel can be located in the driven wheel axle of the intended work load application 7 shown in Fig. 1. The workload chain 5 is size 415.    A chain idler 6 provides chain tension adjustment for the drive chain 5.
[Part9]     The gear box power control system 1 shown in Fig. #1 has two operator controlled modes when the engine is running:   Open and closed:
Fig #4 shows engager in open position
[Part10]     Engager Open position with engine running:    When the operator has the cable control lever 9 in the unlocked open position the engager gears 20 and 21 have no contact with each other and no engine power is transmitted. The final drive spur gear 19 will spin freely on the jackshaft if the centrifugal clutch 12 is engaged.  If the work related wheel such as a bicycle rear wheel is turning, the output drive sprocket 23 will freewheel over run and the jackshaft of the gear box will not turn spur gear 19.   If the operator decides to re-engage the engine power to the closed position no matter if the vehicle is stopped or rolling and as long as the engine is in the low speed idle mode the transition coupling of engager gears 20 & 21 is made smoothly when the shift lever 22 is moved by the operator via lever 9 attached to control cable 8.  It should be noted that the angled teeth on both engagement gears 20 and 21 enhance smooth slide engagement.  Compression spring 34 holds the shift lever 22 in the open position thus keeping the engagement gear 21 in the open position.  The cable stop is 24 held on by bracket 28.   WARNING:  Do not engage the lever to closed position above engine idle speed.    Disengaging at high rpm is not a problem.

[Part11]     Engager Closed position with engine running:    When Engager gears 20 & 21 are in the closed engaged position with each other this allows engine power above centrifugal clutch engagement rpm to travel via centrifugal clutch 12 to affixed spur gear 13 thus turning spur gears 15, 17 and 19 simultaneously.  Spur gears 15, 17 and 19 operate on dual ball bearing supported shafts called out by 16 and 18 on FIG. 2.  The fixed engager gear 20 attached to final drive gear 19 when closed with engager gear 21 turns the jackshaft 18 via the key or spines it rides on thereby rotating output sprocket 23 in the locked rational direction thus driving chain 5 .   The shift lever 22 holds the engagement gears 20 & 21 in the closed position due to the steel cable being locked closed by lever 9 and held in lock position by detent if an optional twist handle is used and by a push button catch if a lever is used.   The cable stop is 24 held on by bracket 28.

[Part12]     If the vehicle is stopped the operator can adjust carburetor air fuel mixture settings at both idle and high rpm without worry of the work related wheel 7 turning.  If need be in an emergency such as a centrifugal clutch 12 failure to disengage at low rpm or a work related wheel bearing failure or flat tire occurring the operator can quickly disengage engine power via the engager control cable 8 and lever 9 thus disengaging the coupling of engagement gears 20 & 21 so enabling the engine to disconnect from the drive chain 5.

[Part13]     Engine off, not running:     The gear box power control system should be left in the open position when engine is off or not running in preparation for the next engine start cycle.  The freewheel sprocket 23 on the engager jackshaft 18 will freewheel should the work related wheel be turning by means other than engine power such as would be case if pushing the vehicle or people pedaling a bicycle or pedaling a pedal wheel boat in the normal vehicle operational manual mode.    Ref. Figure. #10

Fig. #10.  Special Gear box Output Drive sprocket with freewheel mechanism:

[Part14]     Spur gears 13, 15, 17 and 19 are lubricated with grease for efficient operation and noise reduction.  Slight noise may be noticed when first used but will begin to run more quite as the gears begin to wear in.   The four ball bearings used on 2 gear shafts and are the sealed type with high temperature grease.  Centrifugal clutch 12 is a dry clutch operation.

 Install tank on top tube of the bike frame and hook up gas line from tank valve to carburetor inlet.
Install engager optional twist handle or standard push button lever on left side handlebar;

Install throttle cable to carburetor and throttle handle;
Some engines differ in this area so field modification may be required on the part of the installing mechanic.

Test Start engine without chain installed and tune rpm to optimum condition; To start: set choke; and open air cleaner baffle lever and pull on rope: After starting progressively remove choke and let warm up. After test starting, kill the engine and proceed to complete installation process.

Install 415 drive chain around gear box output drive sprocket and around chain wheel sprocket.      
Make chain as short as possible and install master link on outboard side of gear box drive sprocket.   

(  See warning note on page 4 about master link; ) 

New style chain idler with ball bearing supported pulley wheel:

Adjust chain tension with chain idler fastened on bike wheel strut.  At middle span adjust to ¼ “ deflection up and down.  Chain idler can be used on pedal chain side if desired.

Before riding Re-Start engine with bike rear wheel in elevated and check chain and wheel alignment throughout the engine rpm range.  Check engager for smooth in and out operation.   Shift engager in only when engine is at idle rpm.  Shifting out can be done at any rpm.

Installing a bike mid frame wheel stand is recommend; Optional accessory;

Engine Starting and Operation:

NOTE:   Refer to engine owner’s manual included with the engine and follow  starting and operational instructions.


Note:  On some China made engines the crankcase screw head on the right side of the flange opening must be modified so it does not hit the GruBee gear box at the #16 bearing pocket boss area.   To modify, delete the lock washer and file off 1mm from the top of the screw head to gain 2mm total clearance.   After installing the gear box check for air gap clearance with a flash light or paper insert. This problem does not seem to occur when using Honda GXH50 engines but always check for clearance after gear box installation.   ( Do not grind on the gear box bearing boss: )

< from this to this  >
5 piece Rear Engine Mt. Parts accessory Kit;
       #60 Modified Stock muffler with re-routed exhaust pipe that fits inside stock muffler shield buy cutting a slot at the bottom of the shield:   Gas Tank for mounting on rack behind engine to give low profile;   Rack Mount with adjustable legs;  ( Legs not shown )   2 adjustable Extension bars from rack to seat tube or frame if used on a full suspension bike;  If used on a suspension bike extension bars reciprocate with suspension movement and if used on non suspension bike the extension bars slide to a required fixed position and then locked in place.   Special Carburetor for bottom gas tank that can pull gas upward:   
Extension bars and rerouted exhaust: Extension bars shown in inward and outward positions:
Special Order Optional accessories for Bike installation kit:
Optional Gru-Bee HD rear axle kit with freewheel flange made for attaching a 48 or 56T sprocket.   With this kit you can bolt the chain wheel sprocket directly to a freewheel hub flange.   The standard Sprocket to Spoke installation is not needed: Prevents broken spokes and gives true alignment for a pro-shop set up:    The accompanying drum brake ensures safe stops.   Axle has sealed ball bearings with double row balls to ensure long life.     Use of an optional accessory one lever dual brake cable throttle frees up left side handlebar if a push button engager lever is used.

When HD axle is used no 11T freewheel sprocket on the gear box is required.   Use standard shaft and standard 10 T drive sprocket as shown in the gear box assy.    Sprocket on HD axle can then be 48T instead of 56T as when using 11T freewheel sprocket.

[Part15]     Examples of other than bicycle applications for power control gear box :

[Part16]     Example 1.   A motorized paddle boat normally found as a personal pleasure small boat incorporating one to four people seats.  The Honda GXH50 or HuaSheng 49cc gasoline engine can be mounted to the boat framework.  A drive chain attaches to the output jackshaft of the power control gear box system drive sprocket and goes to a much larger sprocket mounted on the boat paddle wheel shaft.  Engager lever and cable installed as required.

[Part17]     Example 2.    A motorized go-cart having four wheels on two axles, a steering wheel and seat for the operator and or passenger.   A go-cart may be in many configurations and work applications to include light cargo hauling or for people transportation.  The Honda GXH50 or HuaSheng 49cc gasoline engine is mounted to the go cart frame.  A drive chain attaches to the output jackshaft of the power control gear box system drive sprocket and goes to a much larger sprocket mounted on the rear drive axle of the go-cart.    Engager lever and cable installed as required. Example 3:  A stationary engine work station requiring small four-cycle engine to turn an axle shaft such as would be typicality found using a circle saw to cut wood but not exclusively.  The Honda GXH50 or HuaSheng 49cc gasoline engine is mounted on the work station frame.  A drive chain attaches to the output jackshaft of power control system drive sprocket and goes to the intended work load requirement.  Engager lever and cable installed as required.

[Part18]     HuaSheng EPA approved engine:

Engine Type

Air-cooled 4-Stroke OHV Single Cylinder

Max Power(kw/r/min)

1.5 KW / 2 HP / 6800

Fuel Consumption(g/kw·h)


Fuel Consumption(L/h)




Net Weight(kg)




Fuel Tank Capacity(L)


Oil Capacity(mL)


Ignition System


Compression Ratio




Starting System




Package Dimensions(mm)


EPA approved HS 49cc and Honda 50cc Engines  are available from your local engine distributor.    
HS 49cc engines are also available to Skyhawk distributors if ordered with installation kits direct from China GAS.