I have addressed this several times. It works for the KLR + several ATV's and many/most late 1970's & 1980's US V8's, for the same reason. Whether one understands an effect has no bearing as to its efficacy. In fact, we often explain empiracal factors by applying faulty theory which isn't recognized because we do not test the explanation. We do this all the time in the course of day to day. "Hindsight has 20/20 vision" expression is a perfect encapsulation.
Cams retarded the exhaust timing in order to increase combustion burn time because of the need to reduce CO levels. It was the most practical means of addressing the problem at that time of engine development. As for the valve timing numbers so favored by people who read articles but haven't worked with camshafts,
"Cams retarded the exhaust timing in order to increase combustion burn time because of the need to reduce CO levels. . . . "
Normk? Not according to the camshaft timing specifications, from 1987 to 2014, I think. Do you have contradictory data?
If so, WHEN did Kawasaki retard
the cam timing on the KLR650 engines? I didn't think they EVER did, from 1987 to the present.
I don't think I qualify as, one of those you refer to as "people who read articles but haven't worked with camshafts." While I would not pretend to be an Ed Iskenderian or a Smokey Yunick, I've degreed and set up a camshaft or two in my checkered and largely wasted past. I have personally dealt with WEBCO (camshaft grinder) before they became WebCam. Yet I defer to your unimpeachable internal combustion engine technical knowledge and expertise.
Now lets look at some of those "figures," which you apparently minimize and dismiss, at least to some extent:
KLR650 exhaust valve timing:
EV opens 57 degrees BBDC
EV closes 31 degrees ATDC
NOTE: Generation 1 data.
With the "MC mod," the Generation 1 exhaust valve timing would be:
EV opens 72 degrees BBDC
EV closes 16 degrees ATDC
(Notations in CRANKSHAFT DEGREES, conventional practice regarding valve timing.)
Now, what is the stock exhaust valve timing on Generation 2s?
If significantly retarded from Generation 1 STOCK exhaust valve timing, I shall humbly stand corrected, and shall note as 2008 the model year when Kawasaki retarded exhaust valve timing, allegedly "to reduce CO levels," an allegation without citation. Maybe so, but . . . I'd appreciate an authority beyond what some uninvolved person posted on an Internet website.
DISCLAIMER: I'm NOT suggesting advancing the exhaust valve camshaft 15 crankshaft degrees does NOT produce an extra 10 % power output across the rpm spectrum, as claimed; I just wonder . . . HOW?