1981 Yamaha xs400 No Power

Message

thespirit · Tue Jul 03, 2007 8:17 am

Thats odd. Is it the fuel line or the vacuum line for the petcock? Most petcocks have two ports in the back, one for the tank to the carbs for fuel and one that will either connect to a vacuum port on one of the carb boots, or on one of the carbs (usually one of the carb boots). Yours could be hooked up backwards. In any event, if your petcock is set to On and not Pri, then fuel should not be flowing out with the engine off. If it is, you may have a bad petcock... If the petcock is in the Pri position, then fuel will flow without a vacuum... but it shouldn't flow out of the vacuum port.

gymrat1964 · Tue Jul 03, 2007 8:18 am

I can see in a parts diagram that there is a piece of tubing that is supposed to be hooked to it. On each of the intakes between the carb and the block there is a port on each. one is capped one is not. Is it supposed to connect to there?

gymrat1964 · Tue Jul 03, 2007 8:23 am

Ok, so it is a vacuum line. It only leaked slightly when it was cranking over. Thanks for your help again spirit. I want to get the bike running and really appreciate you sharing your knowledge with me.

Go Buckeyes!

Sorry!

thespirit · Tue Jul 03, 2007 8:29 am

gymrat1964 wrote:Go Buckeyes!

Sorry!

OH! You just HAD to, didn't you!

Glad you figured it out.

gymrat1964 · Wed Jul 04, 2007 10:18 am

Well, I lived in Detroit for a few years, so I'm a huge Wings fan if that helps.

I have another problem that is driving me crazy. No spark on the left. New Ignition module, new coil, no spark. Messed around and suddenly I had spark last night and had the bike running for about a half hour. Today, no spark again. Polished up all electrical contacts I could find, still nothing. What could be causing this now. It's driving me nuts that I could have it running and then the next day, back to the same problem. Any ideas?

gymrat1964 · Wed Jul 04, 2007 10:24 am

one more thing, I have swapped coils,plugs and wires. Both work fine on the right side, neither works on the left

thespirit · Thu Jul 05, 2007 2:04 am

That sounds like you have a bad connection going from the ignition module to the coil on the left side, especially if you swapped it out. If you have a voltmeter, check the voltage at the coil with the ignition key on, and the ignition switch on. If it's 12V or higher, you are getting a voltage there, if not, trace those wires back and look for shorts or broken wires.

gymrat1964 · Thu Jul 05, 2007 2:36 am

That's kinda what I thought. Voltmeter was at work yesterday, so I wasn't able to test it.

gymrat1964 · Mon Jul 09, 2007 3:45 am

It appears that I had a bad connection on the female side of the plug on the ignition coil. I wasn't getting enough voltage. I ran a direct wire to the coil and it worked fine. When I put the plug back together after crimping down the connector a bit, it started right up and has been running great ever since. Again, I can't thank you enough for your help.

thespirit · Mon Jul 09, 2007 3:52 am

Awesome! Glad you figured it out.

When you have some time, you may want to go find all of your electrical connections and clean them up. Also, check your charging system to make sure it's doing it's job.