03' yz 450 backfiring when kicking.

7 replies to this topic
  • Vinny2692

Posted August 27, 2007 - 04:32 PM


Hi, i have been having some trouble starting my bike after i have been riding it for a while. I try to kick it, and it takes more kicks than usual, and it backfires. What could this be?

  • greentyler

Posted August 27, 2007 - 07:50 PM


not sure how long you've been riding a four stroke, but this sounds exactly what used to happen to me when i first switched to a thumper and always twisted my throttle when kicking... as if i was on my two stroke!

  • Ga450owner

Posted August 28, 2007 - 03:28 AM


Are u using the hot start?

  • jbrooks26

Posted August 28, 2007 - 04:12 AM


1. Hotstart on?
2. Twisting throttle, causing a wet foul? (flooded) is more pronounced when the engine is warm. A cold engine can take a little extra fuel, that could explain why you don't have problems when cold.
3. Valves getting tight, they get tighter when the engine warms up an all of the parts expand.
4. Jetting slightly rich, try turning your fuel screw in a 1/2 turn or so and see if it changes your problem.

Hope this helps.


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  • Vinny2692

Posted August 29, 2007 - 04:59 PM


hmm, ive made shure i wasnt twisting the throttle. But the problem has seemed to go away today. But when i stoped the bike with the kill switch, it didnt seem to want to start withour the hot start. Im confused. Its my first 4-stroke.

  • jbrooks26

Posted August 30, 2007 - 09:45 AM


Sounds like a jetting thing to me, if it is right on the edge then you will run into different problems with slight weather changes. It is not unusual to use the hot start after using the kill switch, especially if the outside air temp is pretty warm and the engine is hot. You will learn the little nuances of your bike the longer you have it and it will become second nature. Do yourself a favor and learn how to adjust your jetting. Keep a good log of what jets you ran with certain weather conditions and altitudes and over the years you will be well prepared for any riding conditions. Hope this helps.


  • Ga426owner

Posted August 30, 2007 - 01:02 PM


if above did not help...you probably need to adjust the valves....if the bike gets harder and harder to start each time.......this is a symptom of valves needing adjustment

  • kubamtx

Posted August 30, 2007 - 01:38 PM


Check you spark plug hole for water (after cleaning the bike) it looks like spark is jumping everywhere

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