I just changed the spark plugs on my 96 YZF600 and noticed that the old plugs were fouled at the tip near the electrode (last threads). The manual calls for NGK CR9s but I bought CR8s, which was all the parts store had though I've read about this not being a problem.

First off the bike starts so much more cleanly now. Low throttle response is much much better. As I say to myself how great the bike is now, I noticed that white/blue smoke is pouring out of the exhaust, after a couple of minutes after the bike starts up. I never had an issue with this before. The amount of smoke is related to the engine rpm, obviously. Is this normal for new plugs (I'm guessing "no")? Or could it be related to using colder plugs than what is spec'd by Yamaha? Sparkplug #3 did not thread out or thread in very cleanly, so I guess step one is to pull it out and inspect it. Anybody experience this before?

Thanks


Modified by GSpeedR at 6:58 PM 4/6/2008

 

Well, I just went out riding for about 30 minutes and throttle response is excellent now and it really pulls when I open it up...though my idle kind of drifted a little bit. I also did not notice any smoking while stopped at red lights; we'll see if it shows up tomorrow morning.

 

That smoke is not caused by the change in plugs at all. Your increased throttle response and smoother running though is. I enjoy doing maintence, and noticing a difference.

 

It smoked again this morning after a minute or two and then disappeared after a couple more minutes. Cylinder 1 was pretty fouled, I wonder if it could've filled with fuel with no ignition and now it is starting to burn it off.

 

the cylinder wouldn't fill with fuel and then slowly burn off. sounds like either unburnt fuel or oil smoke..

does the smoke have a smell? (don't go huffing exhaust gases and pass out)

 

my experience with cars would suggest your valve seats are hammered and slowly giving up. Since its a '96 this seems possible. However using the colder plugs could be causing this, but to be honest I don't know much about colder plugs, except people use them with nitrous. I would give the plugs spec'ed for your bike a whirl first.

 

Sounds about right... it's fairly easy to tell the difference between Fuel fouled plug and an oil fouled plug