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Engine starts to misfire after heating up

Donoman

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Hey guys,

First time poster here. So Ill get right to it. I Had a problem with my bike misfiring before and not being able to start up before which lead me to:
-Replace both ignition coils
-New Plugs
-New plug wires and caps,
-Adjust the points
-new condensers(this was the problem)

Now after all of that, the bike ran fine for a few days and all of a sudden the problem re appeared. The bike runs fine after warming it up and riding for about ten minutes but then The engine feels like it gets rougher and eventually it feels like 2 cylinders start to cut in and out intermittently. Before I replaced the condensers I knew the cylinders weren't firing because the Exhausts for those two cylinders were cold. After I replaced them, those two cylinders fired right up and the bike was running great for a full 3 days. Then the problem re appeared.

I was test riding after replacing the chain and sprockets today to make sure everything worked, and it did, but like i said, all of a sudden the power started cutting in and out and I barely made it back home.

When I got home, I took the points cover off to see if I had messed up some wiring, but sure enough it looked correct, but there was a slight burning smell. Is this normal from the sparking of the points?

my questions are

1. what you guys think the problem is?
2. Is the burning smell normal?
3. Could it be the condenser again, and if so, could there be something causing my condensers to go bad?

Please let me know.. This is my first bike and I vowed never to have to take it to a shop and that I would learn to do all the work myself, but I seem to be stumped.

Thanks guys!

-Donovan
 
Make sure your points haven't closed back up. Hard to set gaps exactly the same on those, better to set one really carefully then read it with a dwell meter if you can find one to then dead evenly match the other set to the first one. Smoother running that way. Could be one point set has worn the pivot point to move around.

The condensers must have firm reliable grounding at the mounts. I don't use expensive exact replacements, rather oldschool smallblock Chevy ones with additional lead length soldered on if needed, super cheap and quality part. If needed I mount them under tank to get them out from under the ignition cover.

You may just be paranoid due to the problems and smelling normal ozone inside ignition cover from normal use. Look at points to see if they are burning and while running look to see how much arcing going on there. A little is normal but a lot not.
 
Where did you get the coils, points, condensors? Have seen issues with some of the cheap crap available off ebay. New means new, new doesn't mean good. The only time I did have issues was when i went with non oem brand ignition parts. But its been years since I have used points as I only run electronic now, maybe the quality isn't there anymore in the parts available nowdays. Next time when it runs rough stop and check for spark on all four cylinders, verify it is loosing spark and not running out of fuel. Then go from there only replacing one thing at a time.
 
Look at points to see if they are burning and while running look to see how much arcing going on there. A little is normal but a lot not.

Yeah, with a bad condenser you'll see a lot of arcing at the points

New means new, new doesn't mean good.

I've bought "new" condensers only to have them bad right out of the box, the same with points.

Get rid of that crap and put in a Pamco or other electronic ignition. Set it and forget it. (also makes it easy to kick start with a dead battery)

verify it is loosing spark and not running out of fuel

Good point, chase 2 gremlins at once and you'll catch neither.


Just to answer the question: A bad coil can fry a new condenser.
 
Obviously if bike not charging you will get a couple days good running to then go to crap. Make sure battery is charged up and try again.
 
Pamco electronic ignition I swear by this because I was having the same type of problem. after installing electronic ignition I never looked back. The bikes running brand new... always a good Idea to check your coils
 
X2, there is no other improvement you can do much better than a good electronic ignition...............once there I've never seen ANYBODY ever want to go back.
 
I had a 72 Norton that acted the same. Found out the points cam was worn out and wobbled, that in turn caused the points to cause a misfire.
The inner core of the points cam was Brass, I had a machinist cut out the brass and replace it with stainless steel and the problem went away.
He had to machine out the brass then make a replacement sleeve of Stainless Steel, freeze the sleeve and heat up the cam then pressed the new sleve into the hole so it would stay tight. Never had a problem after that.
 
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