intermittent ignition misfire

Hello everyone,
I'm new to the sight and recently bought my first street bike. I had a dirt bike but that was about 28 years ago. I now own an 82 yamaha maxim 550.
I have been working on a hesitation problem that it had at about 2500 rpm. Thanks to the posts on here that problem is now gone. Also had a charging problem that I took care of by cleaning all of my connections with electrical cleaner that I read about doing on here. Been a great sight for help so far. Now on to my final problem. There is an intermittent ignition miss. It seems to be effecting #3 and #4 cylinders. I would think coil if it weren't for the fact that they get fired off of two different coils. I found this problem using an inductive timing light and attaching it to the wires one at a time and then watching the strobe on my hand. This miss problem happens through out the rpm range. I have not rode the bike since before I got the hesitation problem taken care of but even when at hiway speeds you can hear the miss in the exhaust. When watching the timing light the missfire happens irregularly. Sometimes its once other times its 2 or 3 one after the other and the time between the miss varies from 5 sec to less. Also the plugs are brand new. Any suggestions on where to go from here?

 

Have you checked compression and valve clearance?

I know you're thinking this is an ignition problem, and you may be right, but I've also seen coughing, popping, problems that seemed like intermittent ignition but were actually caused by a bent valve.

On the ignition side, I'd verify that the resistor spark plug caps are good. They screw on to the ends of the wires and replacements are available online or from some bike shops: NGK LB05F for 1/4, and YB05F for 2/3. They should read 5K Ohms from insider contact to outside contact. The coils themselves should read about 11 - 12 KOhms, not counting the caps - or add another 10K Ohms if both caps are on. Resistance is read HV wire to HV wire, or cap to cap.

If you think it's a bad connection, you can take a dowel or something similar, and poke at the TCI wiring to see if that aggravates the miss. You can also remove the timing cover and see whether poking the pickup wiring, or lightly tapping a pickup, ties into the miss at all.

 

Thanks for the suggestions. Turned out to be the plug wire ends.

 

Yay, we're 3/3

 

Yep. Good job everyone. I swear this bike has got a gremlin. Now I got another problem with the headlight which I will do a new post. Seems like I just get one thing fixed and then within 24 hrs a new problem arises.

 

That's because they're NOT "problems." They're symptoms of neglect and age.

You want it to stop? Take charge of "The Process." Right now the bike is in charge.

Read this: http://xjbikes.com/Forums/viewtopic/t=24010.html and think about it.

 

Very true. I hav e had it for a week and a half now. Guess I will end up knowing it inside and out by the time I get it working right.