Topic: CB500 burning out plugs

[El Taco]

I don't get it. I can put a new set of NGK plugs in my CB500, and they'll get me across town. A set of 4163 Autolites will last a week or two. They don't last long enough to fowl out, they just quit firing.

Any ideas?

[TwoTired]

Any ideas?

Nah.
Might get some, though, if I knew what the plug numbers were, or what the electrode insulator deposit color was. Or, if the ignition was stock. Or, what the plug cap resistance was.  Or, what modifications were done to the bike from stock.

Cheers,
Mr., Surly

[El Taco]

4163 Autolites. Stock ignition all the way. Plugs look normal. On a set of NGK D7EAs, the center electrode's insulator stays white. The Autolites may grey a little.

[TwoTired]

The correct cross for your bike is a 4133 Auto lite.
The 4163 is a resistor plug with a different heat range than called for by Honda.

The insulator color should be tan.  White or light grey is too lean.
I suspect you are overheating your plugs (as well as your cylinders), due to exhaust or induction changes from stock (which is why I asked about bike modifications).

You do run the risk of preignition and/or detonation which can destroy your engine.   
Check out:
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

[El Taco]

You see, I had great fortune with the 4163 Autolite, which was supposed to be the same as a D7EA NGK plug. The D7EA would quit firing before I made it across town. I'd limp up to the Advance Auto Parts store on the east side of town, remove my plugs in the parking lot, and exchange them. I'd install the plugs, then drive across town to the Advance on the west side. By the time I'd get there, it'd be missing like a bastard, and I'd remove the plugs there, and exchange them again. I'd drive away running great.

Well, Advance kind of got tired of it, and decided they weren't going to honor the two year warranty anymore. They suggested the 4163, and I took it. It worked great, but they don't make them anymore. 4163s would last about three months.

They no longer make the 4133. I checked. At least nobody around here can even order them. All the stores suggest a Champion plug, or Nippon Denso. I'm rather afraid to try either, fearing that I might not make it to where I'm going after that.

I've had bikes that ran fine on D7EAs. Could it be something with the ignition system? My points are gapped to .015 if I'm not mistaken. I've had two different sets of stock coils on it. Never changed the condensers, but it runs fine.

[TwoTired]

As I said, I think it is your fuel mixture being too lean.

Godd luck!

[El Taco]

Man, I flat out missed that you mentioned exhaust modifactions. Slipped my mind as well. I feel as though the standard exhaust for an sohc4 is a two into one set with megaphones. I understand the benefit of the four into one, but I tire of the sound quickly. These bikes sound better in stereo. My wife even complains because it doesn't sound right, or it's not loud enough.

I run two into ones with some old Jardine megaphones.....that simply have no baffles at all. I haven't rejetted the carbs. They came off a 75 550E. This is the same carb/exhaust set that I've run on several sohc4s over the years. This was simply the first 500. The previous CB550 I had the carbs on had the same problem. It had the stock, not easy to get rid of, F model header, being an F model and all, and it did the same thing. It was the one that cooked all those NGKs. It donated most of it's parts when the cam chain broke.

[TwoTired]

The carbs all mount onto a common joiner plate.  But, each carb body mount flange has a set up number stamped on the top right.  The numbers I'm aware of are: 627B, 022A, 069A.  These correspond with use on the CB500, CB550K, and the CB550F.  Each uses a different slide needle profile and have other jetting differences, as well.

It is not surprising that carbs set up for a CB550 would run lean on a CB500.  And, the exhaust restriction changes can make jetting and mixture requirements different for the three metering mechanisms in the carbs.
Cheers,

[bryanj]

There aint no such beast as a 550E thats just the start of the engine number! and 550 carbs have different jets to 500 never mind the needle profile so no way is a straight on fit AND THEN you alter the exhaust as well! Sorry you got LOTS of playing to do

[dusterdude]

food for thought,i run champions in my 750,no problems at all.