> A friend and I wanted a bike so, we looked in the classified and found > an ad for a 72' Yamaha two stroke R5 350. The bike was sitting out in > the rain for about ten years. That didn't daunt us so we it rebuilt > anyway. We replaced the lower end, had the pistons rebored and bought a > new battery and sparks. The bike started up then quit.
Been there. Seems like you have a pretty good start on making the bike a runner. We'll get to the electrical problem in a minute. First you need to take care of some other areas before they get to be real problems.
If you don't have one already get a good manual, Clymer or Yamaha.
You made no mention of the fuel system. Here you need to: 1. Empty the tank, remove the petcock and clean that sucker out. If there is rust buy a tank coating kit with an acid wash. Kreem makes an outstanding example.
2. Empty and clean the oil reservoir. Its plastic so it won't rust. Fill with a good quality premix. Golden Spectro or Yammalube.
These items are important because they not only feed fuel, but lubrication to the engine. It is a good idea to add inline filters to gas line.
> I took it into > the shop and they dialed in the points. I took it home, it ran once or > twice. Then it doesn't start again. In fact, it drains the battery. I > know the problem is not the starter because it has a kick starter. I > tried to push start it, no luck. I don't know what to do. And I don't > want to spend a fortune to have a mechanic look at it. When it runs it's > a really great bike to ride.
Sounds like it is not charging. First get a battery charger. They make some inexpensive units. You don't want anything that charges over 1 amp or you may harm the battery. I would recommend getting a "Battery Tender."
They run about $45 dollars but are excellent units that can be used to keep any small battery at full charge without worry.
With the battery at full charge start the bike and hag a voltmeter across the battery. It should read about 14 volts with the engine running about 3,000 rpm. If not , get to checking. Since this thing has set outside so long in the rain I would undo all electrical connections, clean them and stick them back together using a dielectric (conductive) grease.
Recharge the battery and restart the engine. Still no 14 volts? (it will read 12 volts if not charging). You may have a problem in the charging system itself. Could very well be the voltage regulator. Follow the manual in trouble shooting the charging system.
DO NOT ride the bike unless it is charging. If the battery gets low the ignition system can not do its job and the engine will detonate or eat its own pistons. Trust me on this one. It happened to me.
This is a site dedicated to the 1970-72 Yamaha 350 R5 two-strokes. These bikes are surprisingly fast for their size and age, lifting the front wheel in the first two gears and keeping up with modern bikes twice their size. It's also extremely flickable and great fun around the city or carving up canyon roads. It was the direct descendant of the Yamaha factory TR production racers. Dirty, loud, crazy quick and relatively affordable when new (and more so now!), it was, and still is, a giant-killer.
I picked up an R5C for my first motorcycle a few years ago, and was frustrated with the lack of information on these bikes available on the web. The original purpose of this site was to document the process of bringing the R5 back to life. But as I spent time gathering as much relevant and entertaining information as possible into one place for my own reference, I thought it would be helpful to share it with people who are also interested in these bikes, as well as other Yamahas, vintage bikes, and cool motorcycles in general.