Question about Yamaha XJ 400 Motorcycles
If by "pop start" you mean push-start the bike by popping the clutch to turn over the engine, I would suggest that you have one of several problems. First, your battery may be going south, and it may not have the amperage to power both the starter and fire the coils after it's been sitting for a while. However, once the bike has warmed up, the motor is much easier to turn over, and the battery will have had its charge topped off by the alternator. Any auto parts store should be able to test your battery for you for free. You can have a battery read 12.6 volts but be sufficiently sulfated that it has no amps to turn over your starter. A battery can go bad in a single riding season, too, depending on the quality of its construction and the conditions under which it has been used.
If your battery tests good, you might have a flaky connection somewhere in your wiring harness. Check the positive leads going back from the starter itself toward the battery. Pull apart each wiring harness connector and make sure that the bullet and socket connectors are nice and shiny. A pencil eraser will do a decent job of cleaning up bullet connectors; the sockets are a bit more of a challenge. I try to avoid sandpaper for this job because it will gouge scratches into the connectors, increasing the surface area that can tarnish and providing only a temporary fix.
If all this tests out OK, another possible source for your problem is that your starter might be going bad. Some Yamaha starters of this vintage had a weak oil seal behind the starter gear, and oil from the crankcase could leak into the starter, eventually saturating the starter coils and assembly and preventing the starter brushes from making good electrical contact with the starter armature. As a result, it would take more and more juice to get the starter to turn over, until eventually the starter wouldn't work. The fix for this is to pull the starter, crack the case to drain out all the oil (a bit of spray electrical contact cleaner on the armature would easily clean that up), and replace both the brushes (available as a stand-alone part from Yamaha) and the oil seal for the starter shaft. With my '82 XZ-550, after fighting this problem for a number of years, I was advised by a Yamaha guru to visit a seal and bearing shop to get a non-Yamaha replacement for my seal. I can't remember if this is because the Yamaha seal was of inferior quality or because Yamaha didn't sell the replacement seal. At any rate, I was able to get an exact non-Yamaha match for the seal for just a few dollars, and I never had a starter problem again with that bike (I had plenty of other problems, but never with the starter).
Posted on May 17, 2011
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Posted on Jan 02, 2017
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