cautionary tale.

daniel deblanke

XS650 Enthusiast
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los angeles
i haven't been riding the xs a lot lately.

started it up a few weeks ago and realized the battery had died.

tendered it for a few hours and it seemed to be perfect!


Jumped on it on saturday morning and it was bogging hard, no power.

pulled the plugs, one was black the other barely white.


Right here my story could have ended, with replacing the spark plugs.

BUT NO!

NO NO NO

I tried to rebalance the carbs, checked for leaks, checked mix screws, tinkered with idle, pulled hair from my head, drove frustratingly around my neighborhood, emptied float bowls, pulled tank, checked for clean gas, checked advance, etc etc

I wasted several hours over two days, when If I had replaced the spark plugs first thing I would have been happy.

So my two year old plugs were shitty. end of story.

MC is happy again.

I always need to remind myself to go for the obvious, easy answer first!!
 
I find this old bike is rather tough on plugs, wearing them quickly, especially if you still run the points ignition. I routinely replace mine every 3 to 4K miles.
 
I find this old bike is rather tough on plugs, wearing them quickly, especially if you still run the points ignition. I routinely replace mine every 3 to 4K miles.

this one has the pamco installed - but I have to say there are many "BAD plugs" posts on this forum AND other PTW forums I'm on.

my father in Law, thank god, talked me out of pulling the carbs and just said - why don't you replace the plugs and see what happens!

:laugh2:
 
I find this old bike is rather tough on plugs, wearing them quickly, especially if you still run the points ignition. I routinely replace mine every 3 to 4K miles.
Hmmm, weird, I pretty much never replace plugs...
Daniel said one plug was black, the other barely white... to me this suggests an imbalance somewhere...

No to hijack the thread, but I practically never even clean my plugs. When I do, I sand blast them. I carefully tape off the threads which are usually oily so that media does not get stuck onto them. When done, I try to thoroughly clean the porcelain with carb cleaner and compressed air to make sure I am not introducing media into the cylinder. I do this to all resurrections. Been doing it forever. I never buy new plugs.
Somebody tell me why this is a bad idea, I'm listening.
 
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Hey DogBunny, one of these plug blasters was in the garage where I worked as a kid. It was used many times per day. It was connected to shop air. I don't recall what media filled it.
 
Because plugs wear out. The center electrode slowly wears away and gets shorter. Usually, if running well, the plug will still look fine. You need a brand new plug on hand to compare it to side by side. Then you'll notice the shorter center electrode on the used plug.

Years ago on one of my BMWs, I noticed it seemed to be struggling a bit at highway speeds. It still started OK and ran fine, but the performance wasn't quite up to snuff at higher speeds. This was on an out-of-state trip I noticed this. When I got home I checked my maintenance notes. The plugs had been in there nearly 10K miles. I compared one to a new plug and that's when I noticed the shorter center electrode. It still looked fine, all sharp edged and flat across the top, it was just shorter. So, I put new plugs in and problem solved. The old ones were just used up, at the end (past actually) of their service life. So now, I always keep some spare new plugs on the shelf, if for nothing else then to use as a "tool" for judging the wear on the plugs I'm running. But like I said, I routinely change them out every 3 to 4K, even though I'm running a Pamco now too.
 
I will brush my plugs with a steel brush and adjust the gap if necessary. I notice quicker starting if it's been too long. I check the insulator inside for cracking or signs of electrical paths and get a new one if I see that; rare but happens.
 
here is a pic of the bad plugs

badplugs1.png


looks like right side had stopped firing?

so the bike idled and started normal, but had to power, and could barely go up a hill.

like i said - i put all the carb setting back to where i started including the manometered sync screw - i didn't have a second to attach the manometer again but I will saturday.

open to all info and help and opinions- i am only a couple years into this machine and i still rely heavily on my expert level father in law.
 
I heat em GOOD with a propane torch, wire brush, gap, reinstall. But if I continue to have running problems absolutely put in new plugs! When troubleshooting; eliminate the cheap easy stuff first.
My 05 Prius got a plug change at 100,000 miles it didn't need it, I'm at 97,000 miles on my 12 Prius starting thinking I may do a plug change some day.
Since the end of leaded gas plugs "wearing out" is not likely. At really high miles gaps are opened a bit but with electronic ignition and good coils it doesn't matter much.
Dan I suspect the problem's not the plug but I'd for sure be checking plug wires, caps, look at the spark quality etc. That left plug looks lightly fuel fouled. What ignition system do you have?
 
I heat em GOOD with a propane torch wire brush gap install. My 05 Prius got a plug change at 100,000 miles it didn't need it I'm at 97,000 miles on my 12 Prius starting thinking I may do a plug change some day. Since the end of leaded gas plugs "wearing out" is not likely. at really high miles a gaps are opened a bit with electronic ignition a good coils it doesn't matter much. Dan I suspect the problem not the plug but I'd for sure be checking plug wires, caps, look at the spark quality etc. That left plug looks lightly fuel fouled. What ignition system do you have?

i have the pamco in it.
 
The electronic iggy fires both plugs together every time the the crank revolves. But will continue to fire the better plug even if one's fouled. Cheap trick; swap sides if you have one "bad" plug. Watch exhaust temps. A bit of water squirted from a spray bottle on the headers shows it real fast.
 
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Then you should be getting an equal strength spark on each side, unless there's an issue with the plug wire or plug cap on that "black plug" side. Rare, but it's not unheard of. Often the plug cap has just come loose on the plug wire. Give the cap a gentle tug, if it comes right off in your hand you may have found the issue. NGK plug caps I assume? They "thread" into and onto the end of the spark plug wire. If you look in the wire end of the cap, you'll see what looks like the threaded end of a wood screw in there. You "screw" the cap onto the wire until it's tight.

You could also measure the resistance through the cap on that "black plug" side. Again, rare but it does happen, caps can go bad. When they do, their resistance starts to climb and eventually that can start choking off the spark.
 
I'd be suspicious of bad float or needle and seat on the left plug. I'd wait and see if the new plug gets that way.
 
Then you should be getting an equal strength spark on each side, unless there's an issue with the plug wire or plug cap on that "black plug" side. Rare, but it's not unheard of. Often the plug cap has just come loose on the plug wire. Give the cap a gentle tug, if it comes right off in your hand you may have found the issue. NGK plug caps I assume? They "thread" into and onto the end of the spark plug wire. If you look in the wire end of the cap, you'll see what looks like the threaded end of a wood screw in there. You "screw" the cap onto the wire until it's tight.

You could also measure the resistance through the cap on that "black plug" side. Again, rare but it does happen, caps can go bad. When they do, their resistance starts to climb and eventually that can start choking off the spark.

gonna go on a short ride this weekend and have a look at the plugs.

i feel like if it was a carb issue - changing the plugs wouldn't solve problem.

i have ngk boots on the plugs if that matters.
 
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