Topic: carbon on 1 & 4 but not 2 & 3

[briggj]

Hello,

I recently bought two '77 CB550 SS. One looks great (red) and the other (blue) needs some 'TLC'. The red one will electric start and run kinda. But, on the new plugs I put into Red, only two show carbon. The other 2, plugs 2 and 3 look like new. I put in Blue's ignition coils and got the same result. I took the plugs out of Red's 2 and 3 piston and could feel air, that means that my pistons are moving right? I did continuity checks on both sets of ignition coils and they read around 14 ohms. I hope it's a bad ignition coil since one feeds 2 & 3 and not two stuck pistons... I'd apprieciate any help anyone might be willing to lend.

Thanks,
Jason

[Gordon]

If you had two stuck pistons (or even just one) the engine wouldn't turn at all, so that's not the problem.  Sooty plugs generally indicates a rich mixture on that corresponding cylinder. 

[OldSchool_IsCool]

Carbon fouling could be weak spark, but more likely rich carbonation.  Assuming you are running points, you can switch your coils around by switching the blue and yellow wires at the points, then switching the #1 with the #2 plug wire and switching the #3 with the #4 plug wire.  Put in new plugs for a more accurate reading.

If the carbon fowling follows the coil (i.e. 2 & 3 foul) then its spark.  If it stays with 1 & 4 then carbs.

[briggj]

Thank you for the replies Gordon and Old School. I'll give that recommendation a whack.

[750goes]

If it runs "kinda" and plugs 2 & 3 look like new - are you saying that they are not looking like they have been used-  - might I suggest that you may not be getting fuel to 2 & 3 and they are not firing ??

check it by starting the bike and checking the temps of the exhaust pipes - if 2 & 3 are not firing then the exhausts will not get hot...

check for spark on 2 & 3 - put another spark plug into the lead on 2 or 3 (don't remove your old one) and lay it on the head, then crank and check for spark -if you got it then its probably fuel delivery issues..

[Gordon]

If it runs "kinda" and plugs 2 & 3 look like new - are you saying that they are not looking like they have been used-  - might I suggest that you may not be getting fuel to 2 & 3 and they are not firing ??

check it by starting the bike and checking the temps of the exhaust pipes - if 2 & 3 are not firing then the exhausts will not get hot...

check for spark on 2 & 3 - put another spark plug into the lead on 2 or 3 (don't remove your old one) and lay it on the head, then crank and check for spark -if you got it then its probably fuel delivery issues..

Good call!

[briggj]

Thanks 750goes. I have not be able to test the spark tonight. I replaced the spark plugs, that was what I meant by they look new. The pipes on 2 and 3 were not hot, unlike 1 and 4. Plug 3 had gas on it but plug 2 was dry. I hope to be able to test everyone's suggestions tomorrow after work.

Thanks again.

[OldSchool_IsCool]

I think 750goes is onto it.  It's not that 1&4 are running badly, its that 2&3 aren't running at all!  May very well be ignition (points, or coil) on 2.3

[briggj]

It turns out that the yellow wire from the ignition coil to the points, which feeds 2 and 3, was disconnected near the battery box. I appreciate all the suggestions that were offered. Restoring the blue one will be an adventure!

[750goes]

Glad you found the problem - whats up with the blue wire -bit corroded or bad connection as well ?

[briggj]

I actually meant the blue one attached. I picked it up on ebay for $148. I hope to restore it.