New 1981 XS650 need a little help with electrical

[XSJoel]

Hey guys. Just joined today, also picked up a very nice 1981 XS650 from the original owner with less than 9,000 miles on the clock. Unmolested bike in very good condition. Problem is it seems to have some sort of electrical gremlin. It is only firing on one cylinder, PO thought it was the coil so he replaced the coil and got the same thing. And when he reversed the coil wires, the firing cylinder switched as well. So to me that tells me that it isn't the cylinder, must be somewhere before the coil because the coil replacement didn't change anything, neither did new plugs and wires. So I am thinking its before the coil. You guys got any idea what it could be? And I know my explanation prolly didn't help much, but I am just seeing if maybe anyone else had the same issue before so tomorrow I can go check and see if I can catch the problem. Thanks in advance guys.

 

[xjwmx]

Proud '81 owner here. I think the P.O. is pulling your leg a little bit. Switching the wires on the coil (not the plug wires) doesn't have any effect. Also, the way the coil works, if one side is getting spark the other side is too, if the ignition wires and cap and plug are good. Check compression on the bad cyl and if it's good then have at it with the carbs

 

[XSJoel]

Good to know. He gave me the old coil, and it has new Accel wires on it. I am going to run compression first thing and if that is good I will take some readings on the plug wires. He may have said he switched the plug wires, I can't remember, but I didn't know that the coil worked where it's all or nothing, that really helps me on my journey. I would love for it to be the carbs, but I guess time will tell.

 

[xjwmx]

Better the carbs than a hole in a piston, but just barely....

 

[XSJoel]

No problem, I caught the jest of it.

 

[xjwmx]

Both ends of the coil secondary are connected to a plug, but one side could potentially conduct without sparking, a fouled plug, say.

 

[XSJoel]

Yeah, I gotcha. I gotta tear into it tomorrow and go from there. Sitting at my buddies house, or I would be out there right now at least getting my compression test.

 

[xjwmx]

Now that I think about it, I think I've run mine accidentally with one cap off, and I can't figure out how it could run that way,

 

[XSJoel]

Not sure, reading the guides, one says:

"2. The dual output coil has to have both spark plug wires connected to a spark plug at all times."

But I gotta hit the sack, need some sleep so I can get up and work on the bike tomorrow. Thanks for the help. I will be back here tomorrow night.

 

[XSJoel]

So we busted into it and you will never believe what we found. Good compression and good spark. So I guess it's time to rebuild some carbs! Although after reading the guide, I think I am going to let someone else tackle that.

 

[Dennis]

well it sounds like you have enough mechanical abilities to tear the carbs and clean them yourself
They are not that hard

 

[jamesgs4]

81 carbs are simple to rebuild as well, see the kit at mikesxs and youll know what I mean.

 

[remmy1101]

Dont buy any parts unless you have to just clean all passage ways and blow them out with compressed air after the carb clean

 

[gggGary]

+1 parts are optional sometimes especially if you are very careful getting the float bowl gaskets off. however IMHO Float valve o-rings are not optional on BS34's get em replace em. Dodge a ton O grief.
With the plugs out and grounded do you have good spark on both side? When doing a start up I always heat the plugs up HOT with a propane torch. then use a little anti seize on the threads. Can't count how many times that has changed popping into running.

 

[XSJoel]

Thanks for all the help guys. I fired it up and me and my buddy were checking it out and it seems to be running on both cylinders at times, but the right side isn't getting enough fuel is what it seems like. But yes, we have good spark, the plugs look good and the wires are new as well. So I am going to start with an oil and filter change, tear into the carbs and fix the sticking brakes. Also will post pics once I remember to get some.