Running rich, running lean

[Kool_Biker]

Could one of the forum gurus shed some light on the subject matter. Please.
I read ".. my bike has been running a little rich .." or the opposite in the myriad of threads in our forum.
So I wonder HOW one can tell with certainty when this is so, or much more important, when a bike runs "about right". :)
Thanks, Aris

[daves79x]

Pretty simply - with a stock bike (intake primarily) with stock jetting, your bike should get at least 35 mpg during normal riding. Many stock late models get over 40 running normally. Anything less than 30mpg (or whatever that equals in kmpl) and something's wrong. Now if you spend a tank of fuel really honking on it, then the above does not apply.

That's been my experience - I'm sure others will have a different opinion.

Dave

[EMS]

I guess I have always looked at the plugs and/or the exhaust end to get an indication whether the bike is running "rich" or "lean".
A dry, very light tan color on the isolator of the spark plug indicates "lean" and a dark, wet coating means "rich".
Similar at the exhaust side. A dark, wet exhaust tip usually stands for rich and a light gray for lean.
An exhaust gas analyzer is a more precise tool, of course.

[Don]

Most CBX's run a tad on the rich side . . . . hence the 35 to 40 mpg. If they're running much richer than normal you can literally smell it . . . . 'stinking rich' . . . . and the mileage quickly goes south as Dave mentioned

A lean bike will usually pop on decel - One running correctly is just . . . . sweet - Like nothing else you ever rode

Years ago (back in the era of leaded gas) I could tell lots from 'reading' sparkplugs, but now with the unleaded, alcohol-laced gasoline, the differences in color from slightly lean, through correct to slightly rich are so small that looking at the plugs doesn't help me much

Don

[EMS]

Most CBX's run a tad on the rich side . . . . hence the 35 to 40 mpg. , but now with the unleaded, alcohol-laced gasoline, the differences in color from slightly lean, through correct to slightly rich are so small that looking at the plugs doesn't help me much

Don

I would agree with this. This is why I usually check a bike with an exhaust gas analyzer and a dynamometer when it really matters to me. It doesn't really on any of the CBXes.
I remember, we had a great ride on the BRP while in Maggie Valley and my '81 ran two-up like a scalded cat. When we checked it with the exhaust gas analyzer that Larry Benjamin had brought, it was slightly rich and actually richer on 4-6 than on 1-3. I didn't bother doing anything.

[Kool_Biker]

I note in Mike's post above:

" ... when it really matters to me. It doesn't really on any of the CBXes ..."

The way I read it, it is not so critical to worry about getting the mixture spot on on a CBX.
This is fair enough, as we have so much else to worry about

[EMS]

The way I read it, it is not so critical to worry about getting the mixture spot on on a CBX.
This is fair enough, as we have so much else to worry about

That's exactly how I meant it, Aris! And I am not trying to set track records on a CBX or outrun a modern 600cc Sportbike