04 yz450f hard start when warm?

5 replies to this topic
  • macoroniman2004

Posted June 21, 2014 - 06:49 AM


Hey guys recently my 04 450 began starting hard when warm seems to b getting flooded...also while goin slow like 1st gear occasionally it would have zero throttle response and die unless i just let off then it will catch itselfand continue to run...
Bike always starts first kick from dead cold...
I know most will say valves but ive check clearance while cold of course ..three times
Book says intake at .10 to .15 mine are .102 on all three...
Exhaust says .20 to .25 mine are both .21

Now am i still looking at valve job or just shims
Or am i hunting the wrong problem???

Very frustrated any opinions will be valued thanks in advance

  • macoroniman2004

Posted June 22, 2014 - 03:01 AM


Ok update if anyone even read the post lol...
Tore apart bike checked valves for a fourth time ..suprise they are still all right on...

Also cleaned pilot and hot start...neither were dirty but worth a shot...

Now back to starting perfect hot or cold...
One kick everytime after a few priming kicks on cold start ..
Now ive got a valve kit coming so are these bikes worth putting it in as i do not know if they have ever been done
One more thing why the f are yammie shims 9 bux a peice???
When i did my crf they were like 79 cents each
Lol not big deal i spose no wonder this is my first yamaha thumper lol

  • grayracer513

Posted June 23, 2014 - 07:26 AM


Next time use the Honda shims.  Same thing.

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  • macoroniman2004

Posted June 23, 2014 - 01:33 PM


The shims are same diameter and the crf will work just the same? Also is it worth putting the diamond valves in since they are payed for already?

  • grayracer513

Posted June 23, 2014 - 01:57 PM


You mean the Kibblewhite Black Diamond stainless steel valves? Don't use them at all unless you have the spring set that goes with them.  SS is 40% heavier than titanium by volume, so the valves would need heavier springs to avoid float.  If the engine is running OK, and is not in constant need of readjustment of the valve clearance every 5-10 hours, I don't see a reason to install them yet.

  • macoroniman2004

Posted June 23, 2014 - 04:10 PM


Well essentially yes they are black diamond only they are moose brand and come with valves, springs,washers,and top plates,also the seals and buckets (caps)...but so far it has been running better than ever...lol im stumped but also have not got it really hot yet either so ill put the kit on the shelf until after i go on a good ride i just want to replace them before they beat on anything else...not sure if the current valves are stock or not i guess just b a piece of mind for me...bike still does its job for me even being a 04 although i dream of aluminum frame 5 speeds lol

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