1980 XS650 Rough Running/No Start

[bike123]

Hello all. Trying to help my brother work out some issues with an XS650 that has turned into a little bit of a nightmare. Its a 1980 special I believe. He bought it off craigslist as "running perfect", he got it home and immediately the starter motor ceases to function and there was always hesitation during acceleration which he attributed to the carburetors. So I got the carburetors to clean for him which I did, 3 times with the hesitation and a break-up remaining, hence the repeated cleaning attempts. Cleaning involved complete disassembly of all needles and jets and soaks in a heated ultrasonic cleaner. I replaced the seat O-rings, needles, and bowl gaskets, reset the float levels (someone dropped them to ~23mm, probably using the plastic float spec) and essentially cleaned the things to the point that i'm thoroughly convinced they're not the problem. When i say these things are near spotless I mean it. Today he came by so I got to hear and toy with it for myself and from what he tells me its actually been running progressively worse since he got it.

Symptoms are as follows. Wont accelerate past 4000 RPM at WOT. Lots of break-up during acceleration. Exhaust backfiring. Smokes a little when you max the RPMs at ~4k. Idle performance seems to be not bad though it does backfire/pop a little bit. I checked for vacuum leaks and found none.

After coming to the conclusion that the carburetors weren't at fault, at least in my opinion, because its running that bad, im leaning towards the ignition system and tell him as much. He hops on it to go home and its hard to start, gets it going and goes to give it throttle and it just dies out. Doesn't re-start, even with persuasion from starter fluid (engine is now very warm from running for quite some time-yes it had plenty of fresh gas in it). This has all the symptoms of an ignition system that's completely took a dump to me but wanted to see what you fine folk thought and if anyone has any advice as to where to go from here if you've dealt with any similar issues. The bike wasn't exactly cheap to begin with and if possible i'd like to diagnose and replace individual components rather than throwing a $200-$300 ignition kit into it.

Thanks in advance for any guidance.

 

[Conrad Russell]

These bikes have a few elect. problems that are typical.Rotors are one thing too check vibration kills them.Stock ignition TCI needs higher voltage than the points systems did.It sounds to me like you have a problem with the rotor or the coil,old coils on these tend to go bad so use an ohm meter to test coil first,than test the rotor.The TCI box can go bad but thats less often to be the problem.

 

[bike123]

Coil test:
Primary 2.2-2.3 Ohms
Secondary 22.62 Ohms (inc. whatever resistance is in the plug wires)

To me these are good readings. That's cold though so doesn't mean its not failing when it heats up of course but thought i'd try and document this as well as possible as I move along.


Also of note, the battery is toast. I'm sure this isn't helping anything. Getting a replacement asap.

 

[nj1639]

Number one for the battery.....these will not run without a goodun'.
Check the ohms on the rotor, should be 5 ohms, testing slipring to slipring with the brushes out.
Lots of info in the tech section.

 

[5twins]

Yes, without a good battery, these bikes will not run right. As the voltage in the battery gets lower and lower, the bike will run worse and worse, eventually just dieing. Hopefully a new battery will cure the problem.

When he gets it, you'll want to do a simple charging test. Clip a volt meter to the battery terminals. At idle you'll want to see about 12.5, when revved to about 3K, about 14 to 14.5.