Spark Plugs

[SS929]

So I know that a stock tuned bike up here runs rich and I need to change my plugs. I get a set of stock NGKs from Apex. I pull it all apart and get the plugs in ect. Start it up and it sounds like I've got a dead piston right away. Then it goes away, cool mabye um... yeah. So I hop on it and take it for a quick tour around the parking lot. The mid range power just isn't there. So I put it back in the garage and tear it down again just to make sure that I didn't forget anything. Nope its all connected correctly ect. The plugs I pulled out all appeared to be have been burning just a little rich. The coloration on the electrode was a dark brown. The plugs I pulled out were Denso... not sure if that makes a difference as they are both iridium core plugs.
Its an 01 CBR929RR with full yoshimura exhaust, has just under 19k on it.
Any suggestions?

[Mel]

I would start by verifying the gap on the plugs to be sure they are all firing...clean them up with like a wire brush before you put them back in to get the gunk off them. Check the wires and the caps closely, make sure there are no breaks in the wires and that the caps are seated firmly on the plugs.

[rybo]

First, you really don't need to change spark plugs to compensate for the altitude. Your bike is fuel injected and does some compensation on it's own. Now, you have an aftermarket exhaust on as well, so you have two factors changing.

I like NGK plugs, but that is just a personal choice, there are plenty of good brands out there. One thing you have to make sure to do, however is set the gap on the plug. Not doing this can cause the symptoms you describe. Be careful cleaning them with a wire brush as Mel describes above as you can EASILY damage the electrode on plugs with a wire brush. If you are going to do this I strongly suggest that you use a brass brush.

Best of luck to you

Scott

[SS929]

Yeah I was just doing routine maintenance. I've never changed the plugs on this bike before so I figured it must be about time. I gapped them per factory spec. I noticed that the plug wires didn't hold to the old plugs all that well. They did fit snug on the new plugs.
Thanks for the help.

[rybo]

Another thought (message from experience) Did you make sure to get the right wire back on the right plug? I've crossed them before and can say that indeed it equals a "lack of power"

S

[Lee]

You didn't say.

Did you move to a different heat range when you bought new spark plugs?

I'm not an expert on this subject but I know something about it. I specifically recommend that you do NOT use a different heat range than what your owner's manual recommends. If you install colder plugs, your plugs are likely to foul. If you install hotter plugs, you may burn a hole in a piston.

Lee