Curious about engine RPM

[igormon]

When the engine warms up on my Ninja 250 (ie I have been riding for a few minutes) I notice when I stop the engine idles at around 3k for a bit and has a lower "slower" deeper sounding rumble (I have a slip on exhaust).

After a few seconds it drops to 2.5 and the original noise is no longer as deep and it sounds faster, more crisp.

I am not sure how else to describe the "slow" and "fast" thing. I may just post some riding footage here if everyone's absolutely stumped.

Anyway, I haven't noticed any other difference. This started shortly after my winter storage. I stored the bike properly, emptied carbs etc. Only difference is last year the petcock was set to "prime" since he had the vacuum hose disconnected from the petcock the whole time, (previous owner). I didn't notice this until I was prepping for winter storage.

Thanks,

 

[gav.man]

The bike might be running lean. A slip on exhaust sometimes does this. If the carbs got a little gunked up from the storage it may be starved of fuel. My wifes ninja 250 did this and I had to clean the carbs and while I was at it, opened up the idle mixture screw to help it in cold weather. You can try to add a fuel cleaner (recommend Seafoam motor treatment from Canadian tire, add it to your gas tank) to clean out the gunk first. The idle jet on these carbs are TINY!!!

 

[Brian P]

2500 rpm warm idle? Your idle speed is set too high. There should be a small black adjuster knob for this - I don't know that particular bike but on other Kawasaki models, it is on a cable sticking out the left side (above and ahead of the left footpeg vicinity). The owner's book should say what the warm idle is supposed to be (and show where the adjustment is). Failing that, set it to around 1300 - 1500 rpm.