#1 cyl. running rich

[cmawest]

I'm having a problem I can't pin down. my #1 spark plug keeps coming up black while the other 5 are normal, clean, and nice white insulator. obviously its running too rich. I have checked the wire and with a substitute plug it is getting as much spark as all the rest of the plugs. the carbs were gone through last year with all new oem jets. it actually runs o.k. and sounds very good going down the highway, but I stop and pull the plug and its black again. any ideas ?

[Patrick]

Any problem with the air box or intake tube/runner ?

Also wondering about the carburetor diaphragm or spring.

[BonS]

Seconding what Patrick said, I've seen an intake air tube leak cause a black, fouled, rich plug. It's counterintuitave.

[John Schmidt]

I have a problem with the other five. You said they're all "normal, clean, and nice white insulator."  That would seem to indicate those are running too lean if the insulator is "nice white" when they should be kind of a dusty tan looking.  Sounds like you may have more than one problem; too lean on the "normal" five and too rich on the one. Might want to open up the mixture a bit so it runs a bit richer, then start looking for the problem with the one currently running rich. I'd start with the suggestions already given.

[sandy]

Patrick may be on to the issue. If you have an air intake leak, it could be so lean that it won't fire causing a buildup of hydrocarbon on the plug. When I took a carb theory class, this was called a lean miss fire condition. It looks like it's too rich but is actually too lean to fire.

[Ricky-D]

Here is a help regarding reading spark plugs.

http://www.dragstuff.com/techarticles/how-to-read-plugs.html

Gives a better insight in what you are looking at.

The insulator isn't the indicator you think it is!

And besides:



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[cmawest]

figured it out, I appreciate your effort but all were wrong. the air passage into the carb was blocked, took off the chrome cap and sprayed carb cleaner down the hole and viola' runs smooth and all plugs the same color.

[Patrick]

Glad its fixed. But, what hole are you talking about ? Wouldn't that hole have something to do with the diaphragm or slide since the 'chrome cap' had to be removed ?
Since as you put it we were all wrong, I guess we'll not have to help with anything again.

[cmawest]

jeez ! o.k. Patrick, you were all correct, everything you said was right, if you have any problems with a rich cyl. please do everything you recommended here so patrick will be happy and help everyone again.

I really thought you might like to know that your suggestions didn't work and what actually did work. but just so Patrick will be happy and help people again, pretend that you tried everything and it all worked fine.

[The emperor has no clothes]

jeez ! o.k. Patrick, you were all correct, everything you said was right, if you have any problems with a rich cyl. please do everything you recommended here so patrick will be happy and help everyone again.

I really thought you might like to know that your suggestions didn't work and what actually did work. but just so Patrick will be happy and help people again, pretend that you tried everything and it all worked fine.

, Glad you figured it out

[Patrick]

Thats not what I said and why don't you answer the question.