Topic: My brand new plugs turned black after 10 minutes.

[Beastman]

1978 cb550.  Stock, except for a free flowing 4-into-1 exhaust. (I was told this would make the bike run lean, but, well, read on...)

Put my battery on a tender to get some juice back after sitting since autumn.

Installed new plugs, my old ones were pretty black.

Kicked the starter about 100x before getting some signs of life.  Messed with the idle a bit.  I could get the bike to run with the choke out, at 2000-3000 rpms  Any lower than that, or if I released the choke, the bike promptly died.  I could also get it to run with the throttle open 3000-5000 but if I let off the throttle it would die.  If I took it off the tender, the lights began to dim...no starter...etc.  The plugs were black when I pulled them. 

The last ride I went on was 5 miles out, bike died, pushed it home and left it.  That was in August or so.

I bought a volt meter, but I'm not sure where to start with the diagnosis.  Does this even sound like an electrical problem?

[Greggo]

Did you do a full 3K tune up? 

[ADW]

If it won't run except at higher revs that says pilot circuit's plugged to me. Get the carbs off and clean them. Everything. Be sure to take the main jets out and get at the emulsion tubes as well. Run a wire from a wire brush (stiff, yet tiny) through all the holes in the emulsion tubes to ensure they're clean. And also (obviously) through the pilot jets too.

[Beastman]

Why would my plugs be fouled out if the pilot jets were clogged?  Wouldn't that cause the opposite effect?  I'm not an expert, but I thought fouled plugs were from too much gas.  Clogged jets would cause not enough gas right?

[ekpent]

How old is the battery ?. Sounds like it was pretty much shot or dead back in August after your 5 mile failed ride. If its old replace it or start seeing if you have a charging issue. These bikes NEED a good battery to run,hence the crappy start up/performance and probably black plugs. Of course carbs need to be good and clean also,especially if it been sitting for a prolonged period.

Edit to your post--Plugs can be black because your spark is too weak to burn it,the gas, or make the engine run correctly.

[Beastman]

How old is the battery ?. Sounds like it was pretty much shot or dead back in August after your 5 mile failed ride. If its old replace it or start seeing if you have a charging issue. These bikes NEED a good battery to run,hence the crappy start up/performance and probably black plugs. Of course carbs need to be good and clean also,especially if it been sitting for a prolonged period.

Edit to your post--Plugs can be black because your spark is too weak to burn it,the gas, or make the engine run correctly.

I was thinking the same thing.  Weak spark.  Is there an electronics troubleshooting guide anywhere here?  I don't know much about the charging system.  I'll get a new battery if necessary, plug wires too? 

[BeSeeingYou]

If you are running the bike with the choke on it will run rich.  It sounds like your battery is shot and not holding a charge.  That needs to be dealt with first.  These bikes have a weak charging system and at idle and low rpm run off the battery until around 2000-3000rpm.  Weak spark+choke= fouled plugs.  Plugged idle jets like a previous post mentioned can also be part of the problem but you need to get the battery issue dealt with first.

ekpent beat me to it.... need to type faster.  Carry on.

[Greggo]

How old is the battery ?. Sounds like it was pretty much shot or dead back in August after your 5 mile failed ride. If its old replace it or start seeing if you have a charging issue. These bikes NEED a good battery to run,hence the crappy start up/performance and probably black plugs. Of course carbs need to be good and clean also,especially if it been sitting for a prolonged period.


Edit to your post--Plugs can be black because your spark is too weak to burn it,the gas, or make the engine run correctly.

I was thinking the same thing.  Weak spark.  Is there an electronics troubleshooting guide anywhere here?  I don't know much about the charging system.  I'll get a new battery if necessary, plug wires too? 

Bike batteries don't last like car batteries..I was happy to get two seasons out of the 6-volt in my CA95.

[Beastman]

Well, if all it takes is a new battery to get my bike running I'll be psyched.  Will install tomorrow and post an update. Thanks for the help.

[ekpent]

Well, if all it takes is a new battery to get my bike running I'll be psyched.  Will install tomorrow and post an update. Thanks for the help.

  Its one link in a chain but its a big link.