This Moto-Bike had been ridden a lot with the crank loose. As a result, the right crank arm had worn a hole through the swing arm. I repaired the hole by making a patch from a piece of tubing. The patch was welded in place and filed flush.
The gas tank of my first SRX600 was rusty. I eventually got all of the rust out using electrolysis and some phosphoric acid rinses. This took several weeks and lots of intervention. The electrode had to be moved, cleaned and periodically replaced. Also, I burned up a battery charger running it for days on end.
With this gas tank, I used rust911. When I started working on the tank, it only had a couple of pin hole leaks. As rust was removed, more pin holes opened up. I taped over these to keep the tank liquid tight. After a new pinhole opened up overnight and several gallons of rust911 leaked out, I stripped the outside and submerged the tank in a large bucket. The bucket was just big enough to immerse half the tank. I rinsed and flipped the tank every 24 hours. It took about a week to get all of the rust from the tank. I replaced the rust911 solution 6 or 8 times.
According to the instructions rust911 works best elevated above room temperature. I purchased an aquarium heater with a maximum setting of 93 degrees and cranked it all the way up to keep the bath warm. The higher temperature helps considerably.
The seat on this Moto-Bike is in considerably worse shape than the first Moto-Bike. Fortunately the metal on the seat pan is thin and easy to bend back into shape.
A friend in Ohio purchased this Yamaha Moto-Bike at the Barber Vintage Festival and sent it to me for restoration. It’s a 1975 Model B. This makes it a year older than the Moto-Bike I restored for my cousin a while back.
The bike was being ridden when purchased. It is missing the rear fender, chain guard and kick stand. The pedals and handlebar grips are replacement parts and not close to original in appearance.
The crank is loose and the right crank arm hits the swing arm. This has been happening for so long the crank arm has worn through the tubing of the swing arm.
Yamaha’s Moto-Bike was made for three years (1974-1976). There are differences between the model years that makes it easy to identify what year a moto-bike was made. A good collection of photos can be found at BMXmuseum.com.
1974 (A Model):
- Solo saddle with “MOTO-BIKE” silkscreened on back.
- Cottered crank
- Rubber pedals
- The lower body portion of the fork was painted to match the frame.
- The rear fender, chain guard & handlebars were chrome plated.
- Serial number is stamped on bottom side of bottom bracket.
1975 (B Model):
- Same as A Model except…
- Banana seat. The top shock mounting point on the frame was lengthened to provide an anchor point for the seat brace.
- The handle bars and the chain guard were painted flat black instead of being chromed.
1976 (C Model):
- Same as B Model except…
- Single piece crank.
- Rat trap pedals
- The fender and chain guard are made of plastic instead of steel.
- The fork legs are polished aluminum instead of painted steel.
- BMX knobby tires instead of the older diamond tread “Tractor grip” tires on the A & B models.
- Serial number is stamped on right hand side of headset tube.