Yamavolt . left sideYamavolt, right sideOvernight charging
OwnerSeth Masia
LocationBoulder, Colorado United States map
Vehicle1974 Yamaha TA-125
This was a Formula IV road-race bike with a 2-cylinder 2-stroke engine, putting out 29-hp with Vesco pipes. It weighed 180 lb dry and topped out at about 130mph (at 13,000 rpm). In 1976, when the reed-valve engines came in, I parked this bike at the back of the garage. In 2008, I disinterred it, dropped the engine and bolted in a golf cart motor running 48 v. With small SLA batteries it weighs 210 lb.
MotorD&D Motor Systems, Inc. ES 71A 52 Separately Excited DC
Mike Dieroff at D&D was very helpful -- responded promptly to my email, took my phone call and specified a motor that turned out to fit perfectly. No cutting or welding required: I just made a couple of aluminum cradle arms.
Drivetrainchain drive 5.5:1
ControllerAlltrax DCX 300 R11
300 amp programmable (regen) 24-48 v
Alltrax folks also very helpful -- very responsive when I had to track down a fault in the wiring harness I had built (turned out to be a short across a switch).
Batteries4 12v18ah, 12.00 Volt, Lead-Acid, Flooded
Cheap SLA batteries, $38 each from Battery Mart. Hope to replace these with a LiFe pack next summer.
System Voltage48 Volts
ChargerSoneil 4808 SRF
3.5 amp 48vdc output, input 115/230vac
HeaterSummer breeze
Top Speed60 MPH (96 KPH)
Not registered so I'm riding it as if it were a moped -- 30 mph limit. In theory it's geared for 60 and I've gone that fast downhill. Going downhill the bike itself should be stable and safe beyond 90 mph but the motor is supposed to have a 4500 rpm limit. The bike is fun as hell.
AccelerationBrisk to 35 mph.
Range12 Miles (19 Kilometers)
Haven't pushed it beyond 4.5 miles yet -- the distance to the office.
Watt Hours/Mile80 Wh/Mile
City streets, traffic lights, stop signs, mild hills, SUVs.
EV Miles
Current:250 Miles (402 Kilometers)
Seating Capacity1 immature adult
Curb Weight210 Pounds (95 Kilograms)
TiresDunlop 80/90 H18 -- ancient road racing tyres
Conversion Time20 hours
Conversion Cost$1200
Additional FeaturesPlastic Magura twist-grip pot.
Original massive drum brakes aid regenerative braking.
Original racing-crouch riding position with clip-on bars and rear-set pegs.
With no clutch or shifter, there's not much for three limbs to do.
Bicycle LED head and tail lights.
Bike is still sprung for 90+ mph so it's a little harsh on pavement seams. Steering lock is limited so care must be taken maneuvering in parking lots.
Mar. 5: Back in operation for the spring. Batteries are good for only about four miles if air temp is below 40 degrees F. LiFe batteries may fix this.

Dec 10: Parked for the winter, with the charger on a timer so it gets a little juice each night.

Nov 24: Running reliably. I can ride it to work whenever the morning temp is over 38 degrees Fahrenheit and the pavement dry. Side panels are in place so the bike looks pretty nice, finally.

Nov 12: Hard freeze last night and it wasn't kind to the batteries. I barely made it to work. I may have to bring the bike indoors at night -- my garage is unheated.

Nov 6: The bike is running just fine. A short across the throttle switch kept the controller from booting, and it took a few days to diagnose. Controller now boots instantly. Clocks have changed and I'm coming home in the dark, but I'll commute as long as the streets are dry. Meanwhile, as long as I had the wiring apart, I cut a hole in the bottom of the tank to provide clearance for the controller and a place to hide some of the cables. Looks a lot cleaner now.

Sept 30: Rewired to get all the bits under cover. It's a tight fit. Acquired a gold-plated fuse holder for the 250-amp ANN fuse and found room for it on top of the battery stack.

Sept 23: Want an original dolphin fairing to hide the mechanicals, and I also need to weatherproof (that is, hide) the snake nest of wiring.

Sept 20: Commencing daily commute, amongst the migrating SUVs. Feel like a gazelle amongst elephants. Controller sometimes takes awhile to boot -- something is sporadic in there.

Sept 19: We're up and running. Development process viewable here: WebPage

code by jerry