Help. Noob. 2009 yz450f


11 replies to this topic
  • jh101

Posted August 15, 2016 - 05:32 PM

#1

I received a 2009 Yamaha yz450f in a trade around 4 or 5 months ago. Unfortunately that trade transaction was in the middle of my new home being built and completed so I was moving. The bike sat the majority of the time. I'm trying to sell, but the bike will not kick start. I drained and replaced gas, new spark plug with gap of .28, new air filter, but still will not start no matter how many times I kick. Is the only thing left to do is to fool with the carb? I'm looking for guidance and advice. Please in layman terms as I'm quite lame when it comes to bikes. I'm sorry to ask such a silly question, but honestly, I know next to nothing about it. Thank you in advance.

  • stevethe

Posted August 15, 2016 - 05:39 PM

#2

It's likely the pilot jet is plugged. It should just be replaced. The trick is getting to it as its not easy.

  • Krannie McKranface

Posted August 15, 2016 - 06:26 PM

#3

Loosen the boots

Rotate the carb

Don't push to hard or you will crack the hot start nut

Remove the bowl plug and remove the pilot 

 

or

 

Remove the bowl cover screws and remove the pilot

 

The screws are NOT phillips head.

You have to file down the tip of a phillips head 1mm, or you will strip the heads....squirt some PB Blaster on them first

 

If the pilot jet is green with corrosion, you will need to pull the carb and soak it in simple green after removing all the parts (but do not split the body)



  • jh101

Posted August 16, 2016 - 12:28 PM

#4

Thanks for the advice gentlemen. Much appreciated.

  • grayracer513

Posted August 16, 2016 - 01:27 PM

#5

The screws are in fact "JIS cross point" screws.  Often identified by a small dimple on the screw head near the crosscut driver slot.  They are a distinct improvement over Phillips, but they do require the right driver.  I should mention that the straight slot screwdriver used to extract the pilot jet needs to fit the full width of the slot in the jet, which usually means modifying one of your drivers.

 

http://www.vesseltoo...l-products.html

 

The problem with the pilot jet most of the time is a dried film of fuel that can leave the jet looking like it's open, but effectively reduces its size so much that it can't function correctly.  It can be cleaned, but only if you have the right tools.

 

http://www.thumperta...o/#entry6879695

 

Notice in the attached picture that there two discharge ports in the pilot circuit, one above the jet and one above the fuel screw.  Use something flexible like heavy monofilament fishing line to dig out any junk that might be living there.

 

 

 

 

Attached Thumbnails

  • carbcut.png


  • jh101

Posted August 17, 2016 - 01:27 PM

#6

IMG_1471469247.334837.jpg is that lever a compression lever with a hot start button??

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  • jh101

Posted August 17, 2016 - 01:42 PM

#7

Or kill button?

  • grayracer513

Posted August 17, 2016 - 02:00 PM

#8

It's a hot start LEVER and a kill button.  The '06 and later YZF's all have automatic decompression, and no manual lever for the purpose.



  • jh101

Posted August 17, 2016 - 02:17 PM

#9

Thank you. I'm also worrying that my technique for starting the bike isn't correct.

  • Krannie McKranface

Posted August 17, 2016 - 03:22 PM

#10

Thank you. I'm also worrying that my technique for starting the bike isn't correct.

 

 

gas on

kick through with no effort a few times

choke on: throttle closed, kick start

- cold: choke on + 2 or more full pulls on the throttle; throttle closed, kick start. Varies.

 

-you may find you don't need the choke, normally

 

- if it does not start in several kicks, hold the kill button down, wide open throttle and kick several times to clear the cylinder

 

Once running and hot, set the fuel screw at one turn out, and then lower the idle if you can.

Now raise the idle with the fuel screw. Lower the idle if too high.

Repeat till your fuel screw raises the idle to the desired rpm.



  • grayracer513

Posted August 17, 2016 - 03:46 PM

#11

If you were using the hot start as a decomp lever, that may have been fouling you up.  Priming the engine when cold by twisting the throttle as suggested is usually required.  They like the extra gas when they're cold.  The hot start actually works against that.  Its function is to add air into the intake stream to overcome the tendency to have an excess of fuel ("flooding") when at high temperatures.

 

Another thing that messes people up is overthinking the whole TDC thing.  The correct procedure is to roll the engine up against compression and stop there.  Reset the kick crank back to the top and kick it to start from that point without trying to advance it farther. 

 

Here's why:  Without the decompression setup, the intake valve closes at something like 120 degrees before top dead center (BTDC) to start the compression stroke.  Mortal humans cannot kick the engine through that much compression the way the starter and everything is set up, so what you used to do with a YZ426 was to pull the compression release and move the kick crank about an inch so as to move the piston closer to, but not past TDC.  That shortens up the compression stroke and still lets you kick through the spark event to start the engine.  Enter the YZ450.  The auto decompressor holds one of the exhaust valves off of its seat until you get to about 25 degrees BTDC, so that's where the compression stroke starts.  It's already perfectly positioned for a kick right at the point where compression is felt.  If you go past, it you'll have to make the engine go around two full revolutions to get back to a compression stroke again, where it may or may not (probably not) start.

 

So stop at the hard spot, then kick.



  • yz250_TX

Posted August 18, 2016 - 08:47 AM

#12

To start mine I put the gas on, twist the throttle once, then kick. Usually starts in a kick or 3





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