David’s Yamaha Y80 Engine for my Chopper Bike

Yes we finally finished all the body Modifications this Bicycle!  we have stretched it further and lowered the seat, moved the peddal cranks forward, adding a freewheel so when und3er petrol power feet and enjoy the ride.

Where the peddals used to be is right side of bike 2 chain wheels one connects to relocated pedals the other to rear 7 speed freewheel. Okay here is fun part starts… on the othe side of bike on this same axle location (Bottom Bracket) is another freewheel with innerchangeble gears 18, 20, 22T this connects to engine, letting engine coast while peddaling. Neat huh?

Engine is an Automatic so I can shift now with hand lever (located high beside tank to clear legs smile ) I need to get wiring Diagram for this bike to enable me to add Rectifier and Battery (6Volt) and to wire in all our lighting we have done.

I will try to attach picture of bike before engine is added Tank is from a Honda Boss and also uses Honda Front fork/suspension rear is still “Hard Tail” Writing on Tank in Thai says “Thai One On…”

Location Chiang Mai Thailand

Maybe this will get picture loaded  sad ….. if this system is simple….ha! I must be simple minded!!

Well almost finished.  Still need help with wiring.

Is system AC ar DC Voltage?
Is Light system AC or DC voltage??
Is system full wave or 1/2 wave rectification??

All of these I need answers for to rebuild wiring circuits and harness ( would like to boil the Ba-ls on the Mechanic who removed all these components instead of repairing.  Shure bike will run off magneto… but it would really be nice to know I have lights, don’t have to worry about the time and who is riding the Chopper… Ya Know what I mean??

Thai One On Chopper 80cc Yamaha 3 speed Bicycle

Enjoy… pics

Here is the tricks to a safe motorized ride.  (At least they worked for me)
3 freewheels
(1 at crank, 1 at engine connection to bike gearing, last at rear wheel)
we moved crankgear and pedals (BB) forward 18.5 inches lowered seat 14″, used original BB for double gearing.. Left side freewheel to connect to engine… Right side stacked gears (2) 1 on inside connects to crank gear freewheel/Pedals. 1 on outside connects freewheel at rear wheel.

Stacked gear is attached to solid hub so either motor or pedals will coast or connect with rear wheel. Our engine Yamaha Y80M is a kick start semi automatic 3 speed… needs no clutch.  If you need to pedal to start engine then install solid hub on left side instead of freewheel.  Then you must have clutch and a way to lock it engaged to be able to use pedals, when released it engages motor.

I used 100% Motorcycle sprockets and chains.  I chose to use 420 style links as it seemed here I had the option for a 43t chainwheel for my crank.  428 style link chain/sprockets did not seem to have this option.  I also found 4 bolt freewheels that my sprockets bolted rightup to. (See photos)

All I have left to do is exhaust and seat.  Minor adjustments in wiring as I changed from 6V to 12V, Kept Neutral light, added highbeam indicator, changed fuse to Master plugin and 4 circuit fuses.
1: Headlight,
2: Tail Light,
3: Indicators includes horn,
4: Brake Lights


Evan Fell

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