Topic: Intermittant rough running.... a novella

[Scott S]

 Bike is a '78 550K

 1.00 mm overbore
 mild port and polish (clean up, really)
 match ported manifolds
 CB650 cam
 Jardine 4-1
 Pamco ignition, NGK caps, D7EA plugs, coils from Z1 Enterprises
 (I don't see  the coils on Z1 any more, but they're the same as these: 
http://www.ebay.com/itm/Honda-CB-550-1975-1983-Ignition-Coil-/360740342595?pt=UK_Motorcycle_Parts_13&hash=item53fdcccb43 )

  Carbs have been checked, re-checked, checked some more, and cleaned 9 million times. Floats good. Chased jetting all over the place. Ended up back at nearly stock settings....slightly richer on the IMS and 95 instead of 90 on the mains. Plugs look damn near perfect. Scared to go any leaner.

 Valves and timing and cam chain, etc., checked over and over again. Did the 3K mile tune-up twice in less than 100 miles this last go-round. Tried two different mechanical advancers.

 Now that your familiar with the combo, the novella begins.

 *Built he bike and rode it, but it was never quite 100%. Wouldn't reach redline or pull in top gear. The timing on 2/3 was retarded because I ham-fistedly installed the Pamco and moved one of the sensors.
 Pete was kind enough to warrant the Pamco and let me have another.


 * Riding home one night, I noticed that the headlight and gauges were flickering. Installed new Emgo ignition switch. POS Emgo switch promptly fell apart. Cleaned and re-installed stock switch, but it was bad. "Fixed" Emgo switch and re-installed.

 * At this same time,  I installed the replacement Pamco. Promptly started blowing fuses, so I repaired the fuse panel and  installed blade type fuses.

 * Found out I was blowing fuses because I pinched the wires on the new Pamco...DOH! Repaired wires.

 * Now that the electrical was (Supposedly) sorted, I turned to jetting. Since I had the "lean" PD carbs, I started out pretty rich. Raised the needle one clip and went with 105 mains. Bike still ran poorly at high RPM's and wouldn't reach redline.

 * Pulled carbs until I could do it with my eyes closed. Cleaned, cleaned, cleaned. Changed O-rings at manifolds. Started backing down on jets. Plugs are now perfect. When the bike runs properly, it's spot on.

 * Cleaned and changed plugs. Checked that caps are snug on wires. Ohm'ed out the coils. Checked for loose connectors, etc. Verified spark on all four.

 * Installed ANOTHER new Pamco (at my cost) to make sure the repaired wires on the old one weren't causing the problem. They weren't....now I have a spare Pamco.

 The bike has an intermittent "miss"....in that it feels and sounds like it doesn't run on all four, and then it will. No particular speed, no particular RPM. Warm or cold.
 I can just feel and hear that it's not right, then it will "catch" and run like a raped ape.
 Fired it up this morning and could feel it. After about 5-10 minutes of riding, it went away and didn't return. Started bike up again a couple of hours later and it's back. That makes it sound temperature related, but I'm unable to duplicate it. It's completely random. I can't correlate it to any one thing or condition.

 Here are the "uknowns":

 - I can't swear for sure that the Emgo switch isn't cutting out but, if it were, ALL cylinders should lose power. It doesn't feel like that.

 - We were unable to remove the pressed in pilot jets. HOWEVER, we rigged up hoses and blew air and carb cleaner through them until a strong, steady stream was coming from the orifices in the carb bodies. Plus, it's not like it's at one spot on the power band, as if it's not making a clean transition. I feel like the jets are clean.

 - I had a vacuum leak on the choke shaft. The felt washers are NLA, so I split an O-ring and fitted it over the shaft with a little Yamabond. No more leaks (at idle, anyway) and the choke works properly.


 Questions:

 What next!?
 Could the O-ring on the choke shaft cause an intermittent leak? If it DID leak, what does a lean cylinder feel like? What would the symptoms be? I can't find anything on  the plugs that points to one particular cylinder.

 What do failing coils feel like? If they Ohm out OK, is there anything internal that could come and go and cause these symptoms? I can't relate it to heat, vibration, leaning the bike, etc.
 
 I'm leaning towards an electrical/ignition issue, but have run out of stuff to try.
 

[BobbyR]

Trace your wires and connections from the coils down to the Pamco. I had a wire rub through and it would short against the motor and drop two cylinders. When u are dropping two cylinders it is always ignition. I another case someone reported a cracked or shorting plug. 

[DanEarl]

I had a similar problem.  It was a pinched primary coil wire under the gas tank.  I must have pinched it taking the tank on and off.

[Scott S]

 Well, I may have stumbled onto something, simply by typing up the novella. That made me want to take another look at the leak around the choke rod.

 This was a pretty bad leak. I even made a post about it a while back and took a video:

CB550 carb bushing leak?

 I sealed it with an O-ring and some Yamabond, as posted above.



 I started wondering if I was getting an intermittent air leak through there, so I went and poked around with a wooden skewer and took a closer look at it.
 It looked like maybe the O-ring was a little loose, so I pushed it in some more and applied a heavier coating of sealant. Let it sit for about 90 minutes and took it out for a ride.


 It's too early to proclaim victory, but the bike didn't act up AT ALL on a ~30 minute ride through the back roads around here (other than when I forgot to turn on the petcock, but we won't tell anyone about that...    ).

 I'm now thinking that maybe I was getting a bad vacuum leak through there from time to time, making the #2 cylinder run like crap. I'll keep putting some miles on it and report back.

Trace your wires and connections from the coils down to the Pamco. I had a wire rub through and it would short against the motor and drop two cylinders. When u are dropping two cylinders it is always ignition. I another case someone reported a cracked or shorting plug. 

 I'll keep that in mind if this "fix" doesn't work. I've cleaned the plugs and changed them out at least once, but it could be the wiring that runs down the frame to the point where you normally plug in the points. Good suggestion.

[Scott S]

I had a similar problem.  It was a pinched primary coil wire under the gas tank.  I must have pinched it taking the tank on and off.

 What do you mean by primary coil wire? The power wire to the coil(s)?

 I didn't mention it earlier, but I did check all the connections at and around the coils one time when the tank was off. Made sure everything was tight and if there was anything that I even though was making contact and shorting out, I wrapped it with electrical tape.

[DanEarl]

Yes. The 12 volt wire to the coil.   The primary side of an ignition system has battery voltage.  The secondary side (ignition wires, spark plugs) has much higher voltage.   

The problem I had was actually a bad female terminal inside the plastic cover.  It was acting like you said where it would just come and go randomly while riding.  At first I was confused because this happened while I was doing a carb synch.  Then I figured, for a problem to just come and go abruptly like that, It's probably something electric.  Not fuel.

[RAFster122s]

McMaster Carr carries an industrial felt which is what you need to punch/cut a new set of felt seals. Just shipping is a bear from them, so call to find out the total rather than being shocked/unhappy by the cost.

[Scott S]

 Finally gave up and took it to Nate at 2Topia cycles in Charlotte.

 They were able to find and diagnose a bad 2/3 coil, even though it was intermittent. The bike is still at their shop, but they say it runs like a dream with a known good coil in it's place.
 I should have the bike back soon and look forward to having it run like it's SUPPOSED to!

 If you're anywhere in the Charlotte Metro area, I highly recommend Nate and the gang at 2Topia.
https://www.facebook.com/pages/2Topia-Cycles/196010633808627