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Anyone have insight to these issues '10 yz450f

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Ok for those that will want to rip me, its not my first rodeo.

I have had over 50 bikes raced offroad motocross but mainly road racing.

I just sold my ktm 300 exc i now regret!

Purchased a used 450 that is in my opinion a pos.

I am an idiot as didnt ride it trusted it would be a bad ass 450.

I hope wrong due to $$ just spent.


It will start sometimes.

Idles ok for a bit then stumbles finally dies.

If ride it. Soon as rip it a little then off throttle fast it wants to die.

Once hot its crap shoot if will even re start.

Its not hard to kick i have had bikes that required a man to start. Like Husky 610, old beasers to hd's. And Currently my son has ktm 530 and when batt weak it requires a real kick. So its not that and i know proceedure for the 450.

Filter clean, seller did new topend 20 hours ago.

Plug looks sooty. "rich" if carb i would lean it out.

I am at a loss as i dont have access to a diagnostic tool here in Mexico.

As well as parts are a bitch to find.

Hoping someone has similar issue and it was somthing simple.

I must admit short powerband all the hit seems to be in e bottom from the little i have rode it.

Also clutch grabby and not very adjustable, have not pulled apart to see if basket is grooved out from the plates and that is issue?

Any thoughs appreciated!


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My 2011 is relatively easy to start when cold. When it's hot or I stall it, then it can be a real bitch or it starts instantly but never consistantly. It is absolutely imperative that the transmission is in neutral when starting.


The hard hit off idle is a throttle tip in issue and can be softened with a different throttle tube, the GYTR Power Tuner and a heavier flywheel. However, it is best addressed with a throttle body service from Injectioneering. I haven't done it yet but it is on my list of mods.


My first oil change resulted in a grabby clutch. I've since switched oil brands and is very nice now. 

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My 2010 became a little harder to start after about 50 hours. So I had the valves checked . They were all still in spec. But my fuel pump wasn't generating starting PSI until about four kicks. Rather then spend several hundred dollars replacing the fuel pump, I have just chosen to kick it a few extra times. Bike now has probably 80 to 90 hours on it and still working the same. Yours sounds a little worse, and I would start by checking the valves and using the GYTR tuner to reset your ECU to stock map. I agree with the injectioneering mod- well worth it to me. Adding a Yosh pipe helped my top end pull.

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There may be water or dirt in your fuel or fuel pump/filter. I had an issue with my 2010 where it suddenly wouldn't run for very long. I drained the fuel, disconnected the fuel lines, removed the fuel pump/filter and let it all dry out for a day or two. After this was done, the bike had no more problems. It cost me nothing and was easy to do. It may be worth a try. If you pull the pump/filter and it looks dirty, search on here for ways to clean or replace it. My filter was clean so I figured water must have been in the fuel or fuel lines. Good luck.

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Thanks guys,

I hope to dig into it again tonight.

Its just frustrating!! 

On both my Gxxr's I can get the error codes on the dash and address.

All my years of dirtbikes its been Carburators... 

I want to ride this thing! 

Still think i should have kept my 2 smoker!! 

But all my buddies and kids have 4 strokes and I thought would be nice not to have to deal with pre mix...


Again thank you! 

Hope to find resolve before next weekend!!

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Or in our case one ride we do is from Puerto Vallarta basically from the beach thru town, thru rivers and jungle up the mountain and then we get into pine trees etc. Often we spend the night in colonial town San Sebastian del Oeste or Mascota or Talpa de allende. Its real fun. Its about 50 miles ea way. or various loops of around100 to 140 miles. Bringing oil etc is a not so fun... : ) But miss my 300 already and only sold it 2 weeks ago. Love mexico no worries about reg plates lights etc. : )))

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