Originally Posted by TNC

Agreed on break-in. That old method of babying a new engine went out a long time ago when manufacturing tolerances, methods, and materials improved dramatically. It just doesnt apply anymore, at least generally. Now, I'm not suggesting constant, immediate, and continuous redline shifts every time you drive it, but putting around like granny grunt can usually cause more issues than not. I think it can vary a bit from engine to engine based on components and assembly methods, but I thought I remember the Mototune break-in method indicated that if an engine wasn't decently broken-in by about 100 miles, it wasn't going to improve with more miles.

Originally Posted by klx678

First, shifting at the peak horsepower will NOT put you back at the beginning of your power range, it will drop about 1000 rpm in first and progressively less until about 500 rpm in sixth (guessing based on what I've seen on all vehicles). So after looking at the dyno chart any shifting would put the engine right in the "fat" of the torque curve, which brings up another point...

You need to rethink power delivery. Horsepower is a "synthetic number" based on torque, which you may notice will peak at a lower rpm around 7100 rpm - pretty much where the bike ends up if shifted around the horsepower peak of 8200 rpm in lower gears.

Torque is the true ability do do work - the real power. Shifting up around the true peak horsepower will put the engine rpm just beyond the peak torque, which is where the bike will accelerate strongest since it is that point where the ability to do work is greatest.

Your drag racing experience had considerations at true peak horsepower, not over reving by around 2000 rpm like reving a KLX250 to 10,500 when the peak horsepower is at 8200! Your drag racing experience dealt with a real true red line, found with the dyno, not a number that indicates the ability to over rev, which is what most Japanese bikes have. No idea why they do this, but they do.

Every Japanese bike I've seen for decades has had the red line on the tach at least 500 rpm past their own listed peak horsepower rpm and sometimes more. The 1975 Kawasaki 400 triple and my KLX650 both had the redline 500 rpm above peak and both definitely ran stronger when shifted at peak horsepower versus 500 rpm higher. My 1986 Honda Nighthawk S had a red line about 1000 rpm above the claimed horsepower peak, same deal, better shifted at 9500 than at 10,500. Fact is the old Honda Sabre V4 had peak power around 9500 with the tach red line at 10,000 or 10,500. Guys, a friend included, would rev them out to "red line" and miss a shift - 8 bent intake valves. Had they shifted at 9500 they would have had another 500 rpm cushion before damage. It didn't help that Honda didn't have a rev limiter in the ignition, but had the true red line been observed things might not have been so bad.

That is why I look for a true dyno of my machines rather than the tach face. The chart shows where the power is, where the torque is strongest (hardest pull) and where the horsepower peaks, after which the pull falls off. You can tell how the power delivery works. My 550 Zephyr has 80% of its torque from about 3500 rpm to the 7500 peak, horsepower would allow for strong pull up to around 9000-9500.

A look at the torque curve on the 250 would indicate the strongest area of power to run from about 6000-9000 after which it starts to drop off sharper (the reason the bike won't pull red line in top gear easily). It pretty much supports the point I said - shifting at 8200 would likely have the best results since it is at the peak horsepower (which if you notice in the chart is where the torque curve starts to drop significantly) and the shift will drop the engine into its power wheel house.

Consider it taking information at hand to make a good performance decision. Since I can't afford to put the bike on a dyno I will use the on-line chart. How high would you have reved your KLX if they would have put an 8500 rpm red line on it? The high red line is there to give caution, but allow over rev without concern.

Originally Posted by NEWPARTSRULE

Let's see. About 1200km [ around 700 miles ] Your bike is broken in.