2005 YZ450F with 480 bore kit.


12 replies to this topic
  • O_Thizz67

Posted November 23, 2015 - 01:04 AM

#1

My 2005 yz450 is super hard to start. It has a 480 bore kit. When I bought it, I changed the spark plug, air filter, drained the gas, cleaned the carb. And nothing helps. There is times when I can't even get to start. Incredibly hardd to kick, usually have to push start it. Once I get it started, it runs great, until I get to the top of a gear. At the higher end of all 4 gears, the bike will sputter, and pop. I live in Utah, my elevation is around 5000 feet. Changed the jets to bigger sizes to see. Currently have a 195 and a 48 in it. Thanks in advance!!

  • grayracer513

Posted November 23, 2015 - 07:07 AM

#2

At 5000 feet, the air is less dense, so you shouod have gone leaner, not richer, on your jetting.  Take it back down to a 165 main and a 42-45 pilot for starters, and be sure you can get the pilot adjusted for a small RPM drop at around 1 1/4- 2 turns out. 

 

If it's really that hard to kick through, you should have a look at your cam timing.  If the exhaust cam has slipped forward, the auto decompression will also be timied wrong, and you'll have more cranking compression than you should.



  • O_Thizz67

Posted November 23, 2015 - 04:54 PM

#3

When I bought the bike, it had a 165 and a 45 in it. Ran the same way. Sometimes it fires right up, first 3 kicks and other times, it won't even start. Usually it starts cold better than when it's warm. Someone told me to change my accelerator pump, do you think that would cause this type of behavior?

  • Krannie McKranface

Posted November 23, 2015 - 05:01 PM

#4

Accelerator pump will not affect starting in that way.

 

GR is usually spot on on this stuff, and a hard to kick and sputtering top end symtom would point to cam timing for sure.



  • O_Thizz67

Posted November 23, 2015 - 06:05 PM

#5

I had my buddy look at all that, when I first purchased the bike. He said the timing was good. Buhh I'll take it him this weekend and try again!!

  • O_Thizz67

Posted November 23, 2015 - 06:07 PM

#6

Would the fact that it has the 480 bore kit, change the jets I need?

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  • Krannie McKranface

Posted November 24, 2015 - 06:52 AM

#7

Would the fact that it has the 480 bore kit, change the jets I need?

 

Yes, you need to go down on your main jet at least one size.

That could be your problem (gurgling at wide open thottle) if you were already too rich.



  • O_Thizz67

Posted November 24, 2015 - 07:49 AM

#8

Okay so you think I should try maybe a 160? And if that doesn't help. Check my cam timing??

  • grayracer513

Posted November 24, 2015 - 08:48 AM

#9

http://www.thumperta.../#entry12763047



  • O_Thizz67

Posted November 24, 2015 - 08:51 AM

#10

At 5000 feet, the air is less dense, so you shouod have gone leaner, not richer, on your jetting. Take it back down to a 165 main and a 42-45 pilot for starters, and be sure you can get the pilot adjusted for a small RPM drop at around 1 1/4- 2 turns out.

If it's really that hard to kick through, you should have a look at your cam timing. If the exhaust cam has slipped forward, the auto decompression will also be timied wrong, and you'll have more cranking compression than you should.


And by the pilot be adjusted are you talking about the little knob just below my carb? The one to adjust the idling??

  • grayracer513

Posted November 24, 2015 - 09:04 AM

#11

The original screw is not equipped with a knob, but a number of the aftermarket ones do.  The screw requires occasional fiddlingh to adjust for changes in weather and whatnot, so the knob facilitates this. 

 

http://www.thumperta...-mixture-screw/



  • O_Thizz67

Posted November 24, 2015 - 10:05 AM

#12

Okay, I know what you're talking about. So turn that about 1 1/4 -2 turns out? With the 165 and 45 jets. And that doesn't help, I'll check my cam timing again!! Thank you!

  • grayracer513

Posted November 24, 2015 - 01:18 PM

#13

No, not exactly.

 

http://www.thumperta...ircuit-setting/







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