I ahve recently bought a kawasaki kx450 and i want to be able to really look after it (its my first new bike) so im trying to improve my mechanical knowledge!

With a kickstart, when you move it down it suddenly goes from loose and easy to push to really hard, initially i always thought this was the ratchet system of the kickstart starting to move the piston up/down. But i was informed that its actually starts moving as soon as you move the kickstart down and that its actually the gas and air mixture compressing in the cylinder right? So once it starts compressing and gets hard then generally you move the kick lever back to the top so you can get a full kick on it. so why is it that once the cylinder is compressing the air and gas and you move the kick lever to the top its not hard to push down straight away? Even tho where it gets hard to push is slightly higher its still not at the top. Why is that?


The initial part of the movement is to engage the mechanism, once it gets harder to move then you are starting to move the piston.

  • So is it really bad to kick before the ratchet is engaged? Like can it damage is a lot? – Sam.jowy Jun 20 '17 at 9:41
  • most people get the mechanism engaged, get the piston in the right place then do the kick - why should you do different? – Solar Mike Jun 20 '17 at 10:14
  • Can you feel when the mechanism engages? I guess it gets harder to push because all of a sudeen you're moving the actual piston? Also whenever ive started a bike I've moved the lever down until it gets hard and then taken it to the top and kicked from there, is that the correct way to start it or should you go a bit beyond the first bit of resistance? Thanks for the answer and help – Sam.jowy Jun 20 '17 at 10:25

Virtually all dirt bikes have some sort of decompressors on camshaft, and most of them have auto-decompressor, which acts below certain RPM. So when you kick slowly, it will keep valves open, so that it's easy to "prime" it. When you do hard kick, then you are exceeding minimum RPM, and auto-decompressor stays close and you can start the engine.

I don't know how it is on KX450, but on Honda dirt bikes you can kick forever without resistance if you don't kick hard.

  • So what is the gap when the cylinder is in the right place from when the top of the kick starter and where it gets harder to push? – Sam.jowy Jun 20 '17 at 10:44
  • I can assume, that when you compress the air, and let the kick start lever back, during that time your piston moves back. – oryades Jun 21 '17 at 10:04

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