Yamavolt . left sideYamavolt, right side
OwnerSeth Masia
LocationBoulder, Colorado US map
WebWebPage
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). I 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
Motor weighs 38 lb -- twice as much as an Etek but it offers regen braking and is a perfect fit for the chassis. 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
Batteries4 12v18ah, 12.00 Volt, Lead-Acid, Flooded
Cheap SLA batteries, $38 each from Battery Mart.
System Voltage48 Volts
ChargerSoneil 4808 SRF
3.5 amp 48vdc output, input 115/230vac
HeaterSummer breeze
InstrumentationNone
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.
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:200 Miles (321 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.
Nov 12: Hard freeze last night and it wasn't kind to the batteries. I barely made it to work. If I'm going to ride in cold weather, I may have to bring the bike indoors at night -- my garage is unheated.

Nov 6: The bike is running just fine. After a couple of days of troubleshooting, I traced the problem to a short across the throttle switch -- not a controller problem at all. 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.

Oct 8: Bike has been on the stand for a week -- the controller no longer recognizes a throttle signal. Talking to Alltrax to diagnose this problem: the throttle is an unimpressive bit of plastic with a wimpy little potentiometer, but it tests out on the multimeter, and a second 5K pot returns the same result when hooked to the controller.

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

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