04 yz450 break-in

5 replies to this topic
  • veryworried

Posted March 19, 2005 - 07:34 AM


i got a new 450 last week, and followed the manual procedures for break-in. i've mostly ridden big bore 2 strokes and maybe i'm just not used to the thumper. it's hard to start, lots of kicks, and sometimes i have to give it gas to get it to fire.it also seems as if during those kicks it gets real easy to kick. also heard a strange buzzing sound in the top of 4th. could i have screwed something up or am i worried about nothing.bike is stock and i live at 6500 ft.

  • John_Lorenz

Posted March 19, 2005 - 07:43 AM


you may need to reject for you altitude after doing 1, 2 & 3

The last part is the Drill Starting Drill

  • sirthumpalot

Posted March 19, 2005 - 09:10 AM


Should be easy to start once you learn the drill. Hopefully someone else who is near your altitude will chime in with some jetting suggestions. Most often 4-strokes don't like throttle during the kick, and don't be afraid of the hot start. In regards to buzzing in 4th, not sure what you mean. These things have rev limiters so over-revving related break downs are rare, but can occur if you downshift while going too fast and overrev it that way. When you hit the rev limiter it sounds like the motor is starting to miss like crazy. If you're used to big bore 2-strokes then you'll probably pick up on the 4-stroke easily. Have fun!

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  • grayracer513

Posted March 19, 2005 - 09:53 AM


If it's a new out of the box bike, it's almost certainly too rich for your altitude. They're particularly fussy about the idle mixture, and that will affect how well it starts. Look up the idle mixture adjustment in your manual, and plan to buy an extended fuel mixture screw, so you can more easily keep it trimmed.

Idle mix on the modern four strokes is backwards if you're used to 2-strokes or older bikes. The screw meters fuel, not air, so in is leaner, and out is richer.

The starting procedure posted was for an '02 or earlier, and it's applicable except, of course, for the references to a compression release. For cold starts, the choke is usually not enough. I give mine 2-3 twists of throttle so the accelerator pump will prime the engine, then crack it open just off idle and it's a one kick deal. When everything's perfect, they will start at an idle most other times, but things are seldom like that. If you fall, or stall the engine, it will be partly flooded, and usually want a little more air to go with the gas. In these conditions, opening the throttle about a quarter to a third will help. Mine does not like starting with it's nose up or down very far, either.

What you have to learn is not to "twist as you kick" the way so many two stroke riders do. If you open the throttle to start it, throw your thumb over the throttle drum or grab the front brake to help you avoid doing the twist.

The auto decompressor lifts one of the exhaust valves off the seat as you approach the compression stroke, and reseats it just before TDC. If you bring it up to the "hard spot", return the crank to the top, catch the ratchet again and kick smoothly all the way through, it will start better, but you can kick it from pretty much anywhere, too. Starting in neutral sets the ignition timing differently (that's what the neutral switch is for). I once had mine kick the living crap out of me restarting a cooled down engine in gear, so I avoid doing that whenever I can. It nearly broke my foot right through my A-stars, and it took ten minutes to walk it of. :)

You've got a great bike. Learn to "communicate" with it. The better you understand it, the more it will do for you. :)

  • condog_aus

Posted March 19, 2005 - 12:43 PM


Mine was a complete bitch to start till it loosened up after several hours riding. Now its first kick most times, second sometimes, No throttle or the tiniest tiniest bit of throttle. Definitely choke or hot start needed every time without fail, depending on whether its cold or hot.

Dont worry it gets easier. In the first few weeks all i could think was "How the hell am i guna start this pig in the middle of a moto if im stuffed?" But im pleased to say ive done so easily on a two occasssions.

  • mayday

Posted March 19, 2005 - 02:35 PM


I bought an 04 450 ( still in crate) and followed the break in instructions per manual. I noticed when the bike is warm I have to use the hot start (H/S)for a 1 kick start, if not It wants several kicks if H/S is not used. Also my buddys who ride 2-smokers have trouble starting it. It takes time to get used to starting a thumper. Take your time to get used to it :)

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