Chain slap and jetting. sort of.....

Well I have always have had a little chain slap on my WR450, and could never really get rid of it. Well, I was on a fire road last Sunday and really listened to the noise. I put my head down near the engine, as I was never really sure if it was detonation or chain slap. Well, the sound near the engine(it is hard to hold your head low going 50MPH) was definatly detonation. It sounds very similar to chain slap. Well, it turns out, my first 150 break in miles was full of detonation. Probably not a big deal, but I'm sure glad that I found it early. A couple clicks on the needle fixed the problem. I suggest that everybody that has the "chain slap" noise first adjust the chain to spec., and pay attention to the sounds your bike makes. Detonation is hard on your crank, piston and valves. Just FYI.


I originally heard what I thought was detonation on mine when it was new. After asking a few questions it was suggested to take a short ride w/o helmet ( yes I know its a bad idea), after I rode up the hill in my yard I could tell without a doubt it was drive chain slap.

That sound really seems to ring thru the frame.

Another thing I considered. When new all these things have the glowing header syndrome, a lean condition that is much more lean than you probably are (or were)

Oh, it still glows red. I thought that it was normal? My twin streetbike used to always do that.

My bike makes a chain slapping noise(maybe detonation?) at the front sprocket if I lug it down way low. But never hear nothing as long as I'm over 2000 rpm's.

I run 91 premium with a shot of octane boost. It has always been my belief that detonation occurs from unstable fuel igniting to early because of the high compression. High octane stabilizes the fuel so that it wont ignite from the extreme compression, and will wait for the spark. Or your ignition timing is set to far advance, or you have carbon build up that is glowing red.

Does any one know if incorrect air fuel mixture by itself will cause detonation? If so please explain.

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