2005 YZ450F hard starting except when warm

6 replies to this topic
  • dattorob

Posted December 28, 2014 - 07:04 PM


HI there,


I have recently had my engine rebuilt with new valves etc.

Unless the bike is warm it can be quite hard to start as in more

than 5 kicks.

I have googled and search TT and have found a few things to check

such as :


·         Try iridium plug It is just CR8IX

·         Check boot is sealing ok

·         Check pilot jet??


Also found one suggestion about changing starter jet (mine is 72) and

also another about removing neutral switch. Has anyone tried these






:aussy:  :goofy:

  • grayracer513

Posted December 29, 2014 - 07:32 AM


Is this unusual for the bike?


If the pilot jet were partly blocked, it would also run poorly when warm (bogging, stumbling, etc.).  On the other hand, it's fairly common to have one block up if it sits for a while in warm weather.  Try this, and be sure to check the starter jet as well:



  • dattorob

Posted December 29, 2014 - 08:51 PM


Thanks Gray, you're scholar and a gentlemen :) .

i guess its never been an easy starter, i think partly could be i have non-OEM boot clamp between boot and carb and

may also be i got bit of water up one of overflow pipes when washing it.

What should i do with starter jet? i guess check its clean etc.

Also being a big bore requires extra bit of oomph to kick it over it think.

The only other thing i can think is my process/method for strating it

is slightly flawed as in i don't blip the throttle to prime it, so i will add that in.



Robert  :ride:

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Wiz636

Posted January 03, 2015 - 12:55 PM


Years ago I quit trying to clean jets and instead simply replace them.


On my '08 when cold I would find the compression stroke with the kickstarter, give it two full twists of the throttle, then kick it over and it usually started right up.

  • dattorob

Posted January 03, 2015 - 08:07 PM


I would have thought cleaning with carb cleaner and using compressed would do the same trick.

But yeh i do need to alter my starting technique i agree. cheers

  • grayracer513

Posted January 04, 2015 - 07:35 AM


I would have thought cleaning with carb cleaner and using compressed would do the same trick.

But yeh i do need to alter my starting technique i agree. cheers


The pilot jet is too small for that to work most of the time.  Read:



  • dattorob

Posted January 04, 2015 - 02:17 PM


Ok wow that is small. You have a point. Cheers

Related Content


Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • - - - - -
  • 0 reviews

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.