freddy3
XS650 Addict
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No. Condensers either work or they don't. Can't recall ever seeing one intermittent.
Thank you.
No. Condensers either work or they don't. Can't recall ever seeing one intermittent.
Check all your ground wires it is the only thing common to both sides of the 2 ignition circuits
Bad camshaft bearings or worn advance shaft bushings, allowing the points cam to move around, is at least a theoretical possibility.
I once came across that kind of problem on an RD350 with bad main bearings. New bearings fixed unstable ignition timing and cylinders cutting out.
On that RD, it wasn't obvious until I checked the timing with a strobe lamp.Not to be argumentative, but if the bearings were so bad that they were causing alternating cylinders to cut-out....and, sometimes, normal operation....wouldn't there be other issues? Bearing noise, overheating, etc.?
Anyway, removing the points cover, and checking the points cam for any movement or play is pretty quick and easy.
What about poor connections at harness connectors, in the ignition lock (main switch), kill switch, etc?
Lots of possibility for excessive resistance and voltage drop. Try testing with a direct wire from battery+ to coils+, and see if that fixes it.
As I have mentioned numerous times, the original current path (wiring, connectors and switches) from battery + through coils and points to ground is extremely convoluted and likely to cause problems.
If a direct wire seems to fix the problem, you may want to look into installing a directly fed relay, and just use the original supply for relay control voltage
We will find it after a while and with cooperation
If it runs on both sides ( properly ) carburetor and spark and timing is about right
No reason to believe a lacking air supply
I am at a poor power supply or poor ground wiring ..It is the perhaps most common ignition problem
The bypass wiring is helpful in testing which I have had god experiences with.
But feel free to service it downstream from battery to ignition ..or upstream from spark plugs It can take longer time but is one way to do it also.
intermittent problem can be difficult to find A voltmeter installed can help.
Had very similar issue on my '81 special ll. Intermitent dead cylynders and backfiring then it would sometimes come back to normal when riding. I suspected everything from carbs to plug wires. Turned out to be a worn ignition (key) switch. The internals were getting loose and not always making solid contact. As your guy says. "A single part shared by both sides on the cusp of failure." Not sure how similar our models are butt it's a possibility.
I think sometimes we tend to overthik these problems and overlook the simple stuff.
Intermitent dead cylynders and backfiring then it would sometimes come back to normal when riding.
One option that is NOT an option is modifying the original layout of the bike. I realize there're many ways to improve the XS2 and remedy its many inherent limitations, but my goal is to fix/get the OEM components to work to spec, as I've done for 45+ years, every time I've had to solve one of these perplexing problems. I've got vintage OEM cars that I deal with similarly. But I appreciate where you're coming from (trying to solve the problem).
Only two places (electrical) I can think of that would affect both cyls at separate times...
The power wire from the kill switch goes down to the coils. It goes from a single wire to a dual in-line bullet connector that splits it out to both coils. Highly unlikely... but it's possible it's intermittently losing contact on one cyl or the other. Might try crimping it just a little and cleaning it to see if that helps.
The other place would be the mounting of the condenser pack. Both condensers go to ground on the same mounting screw. If it's loose or dirty it could intermittently affect both cylinders.
Those are the only two points I can think of where both ignitions systems have commonality.
Finally, any "electrical check" done without a multimeter (actually volt and ohm meter) is not really telling anything. Measuring coil primary and secondary resistance, then checking voltage at coil + under load (points closed), then voltage drop across points (again closed) is the only way to verify that the ignition circuit is in fact as it should be.
That condenser is a pain to get to. Good luck on finding the problem. Where do you live?