Back with a new build! 5HP 29" Mountain Bike, top speed 51 mph!

Hello All,
I know I haven't been active for a while on this forum, mainly because I have been busy with school and other academic stuff. Since school is out now because of Coronavirus, I have had plenty of time to work on projects in my garage (I still have online classes though). Last December, I crashed my motorized bike and broke it beyond repair. Thankfully I had the proper gear (helmet, gloves, elbow and knee pads) on so I walked away fine aside from a few bruises and scrapes. The bike had a lot of issues anyway and wasn't working well so I decided that I would start building a new and improved motorized bike from scratch. Five months later and it's finally finished! I got the money to build it from mowing lawns and doing yard work around my neighborhood (thankfully people pay very well for lawn service since gardening companies rip people off). Attached below are some photos and a list of the parts, modifications, and specifications of the bike.

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Road Specs:
Top speed (flat surface): 51 mph
Engine Horsepower: 5 HP (number from identical engine and setup on dyno from Zeda Motorsports)
Engine Displacement (US): 70cc

Modifications and Parts (all done and installed by me):
Mountain Bike frame
Custom orange/red paint job
29” V-Spec Wheels
29 x 2.1 WTB Thickslick Tires
Installed travel limiters on front suspension fork for rigidity
Shimano MD-M280 front disc brake
Sintered/Full Metallic front brake pads for increased stopping power
Shimano T4000 Rear V-Brake
Rear Kool-Stop Mountain brake pads for increased stopping power
Motorcycle-grade dual-pull brake lever with parking lock
Adjusted braking power to front and rear (about 80% front, 20% rear)
Upgraded throttle grip and housing
Aftermarket throttle cable
Upgraded handlebar grips
Aftermarket clutch lever with lock
Upgraded spark plug wire and boot on CDI for increased durability
NGK B5HS Spark Plug
Upgraded clutch pads to metallic (black) pads for superior grip and durability
Custom CNC Aluminum clutch flower nut for easier and more precise clutch adjustment
Sanded clutch pads for maximum grip on both flywheels
Schwinn Beach Cruiser Wide Dual Suspension seat with gel cover
Upgraded 3 liter gas tank (painted blue)
Upgraded fuel line and filter
Back wheel kickstand
CNC rear sprocket hub adapter (1”)
36T rear sprocket for maximum speed
Upgraded 415H engine drive chain
Modified spring chain tensioner (angled to align chain)
Professionally ported Zeda 80 (painted blue)
Custom-made angled 20mm I.D. intake for Mikuni VM18 carburetor
Fully tuned/rejetted Mikuni VM18 Carburetor (65 main jet, 25 pilot jet)
UNI High-flow 2 stage air filter
Custom-fit Genuine MZ65 Expansion Pipe (Painted orange with exhaust paint)
Dirt bike muffler added to expansion pipe
Upgraded and port-matched exhaust and intake gaskets
 

darwin

Well-Known Member
Joined
May 26, 2008
Messages
4,787
Need some dark shades to look at that bike. Nice bike though. Does it glow in the dark?
 

msp4662

New Member
Joined
Apr 23, 2020
Messages
13
NICE
I need a good balanced motor by what you got going on were should I buy a motor from and does the silencer kinda quite it down or does it still sound like a big bad chainsaw,80cc yz ,or 80cc rm
 

Sidewinder Jerry

Well-Known Member
Joined
Mar 14, 2011
Messages
2,508
Hello All,
I know I haven't been active for a while on this forum, mainly because I have been busy with school and other academic stuff. Since school is out now because of Coronavirus, I have had plenty of time to work on projects in my garage (I still have online classes though). Last December, I crashed my motorized bike and broke it beyond repair. Thankfully I had the proper gear (helmet, gloves, elbow and knee pads) on so I walked away fine aside from a few bruises and scrapes. The bike had a lot of issues anyway and wasn't working well so I decided that I would start building a new and improved motorized bike from scratch. Five months later and it's finally finished! I got the money to build it from mowing lawns and doing yard work around my neighborhood (thankfully people pay very well for lawn service since gardening companies rip people off). Attached below are some photos and a list of the parts, modifications, and specifications of the bike.

View attachment 94591View attachment 94592View attachment 94593View attachment 94594View attachment 94595

Road Specs:
Top speed (flat surface): 51 mph
Engine Horsepower: 5 HP (number from identical engine and setup on dyno from Zeda Motorsports)
Engine Displacement (US): 70cc

Modifications and Parts (all done and installed by me):
Mountain Bike frame
Custom orange/red paint job
29” V-Spec Wheels
29 x 2.1 WTB Thickslick Tires
Installed travel limiters on front suspension fork for rigidity
Shimano MD-M280 front disc brake
Sintered/Full Metallic front brake pads for increased stopping power
Shimano T4000 Rear V-Brake
Rear Kool-Stop Mountain brake pads for increased stopping power
Motorcycle-grade dual-pull brake lever with parking lock
Adjusted braking power to front and rear (about 80% front, 20% rear)
Upgraded throttle grip and housing
Aftermarket throttle cable
Upgraded handlebar grips
Aftermarket clutch lever with lock
Upgraded spark plug wire and boot on CDI for increased durability
NGK B5HS Spark Plug
Upgraded clutch pads to metallic (black) pads for superior grip and durability
Custom CNC Aluminum clutch flower nut for easier and more precise clutch adjustment
Sanded clutch pads for maximum grip on both flywheels
Schwinn Beach Cruiser Wide Dual Suspension seat with gel cover
Upgraded 3 liter gas tank (painted blue)
Upgraded fuel line and filter
Back wheel kickstand
CNC rear sprocket hub adapter (1”)
36T rear sprocket for maximum speed
Upgraded 415H engine drive chain
Modified spring chain tensioner (angled to align chain)
Professionally ported Zeda 80 (painted blue)
Custom-made angled 20mm I.D. intake for Mikuni VM18 carburetor
Fully tuned/rejetted Mikuni VM18 Carburetor (65 main jet, 25 pilot jet)
UNI High-flow 2 stage air filter
Custom-fit Genuine MZ65 Expansion Pipe (Painted orange with exhaust paint)
Dirt bike muffler added to expansion pipe
Upgraded and port-matched exhaust and intake gaskets

If you want just a little extra comfort get an adjustable suspension seat post. I've hit down hill speeds of 50+ mph and know you can feel the slightest little bump in the road going that fast. Your back will thank you for getting an adjustable suspension seat post. I too use a duel spring seat and have front suspension with 2" wide slick tires.
 
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