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BradZ

Yz450f needs choke to start when hot?

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Anyone know what this could mean? If you try kicking it without choke whilst its hot it just refuses to start. Choke on, first kick..

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My guess would be the carb needs cleaning or fuel is not getting to the carb properly.

Or something is in the wrong way inside the carb.

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What button are you calling choke the red one or black one,red is for hot start and black is for cold.If the 2010 even has a hot start cant remember off the top of my head?

You might need to richen up the pilot jet( turn out) these bikes are tempermental to temperatuer get your self a quick adjust pilot screw like http://www.ebay.com/itm/BLUE-ADJUSTABLE-PILOT-FUEL-MIXTURE-SCREW-4-STROKE-YZ250F-YZ450-WR450-CARBURETOR-/150629705741?pt=Motorcycles_Parts_Accessories&hash=item23123ae80d&vxp=mtrmake life much easier

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No red parts on my bike whatsoever. Im taking about the knob on the throttle body which also adjusts idle when turned. My bike is fuel injected so I might need to get it tuned? No jets to change lol.

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oops my bad when you were talking choke my mind went straight to carbs as most fi systems dont have choke.

not much you can do unless you have the scan tool to check the coolant temp sensor,tps angle ect...

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Just cleaned and re oiled filter lightly. Still hard to start. Hopefully a tune will sort it out unless anyone has any other ideas

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you just replaced the filter yet it's behaving like there's no filter in there!

answers needed here

was this problem evident before the filter change??

is it the correct one and seated right??

Can you compare it to the old one, or even put the old one back in to try??

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Here are your base map settings http://www.yamahamotorsports.com/sport/mcy/2010_yz450f_GYTR_Power_Tuner_settings.aspx and here is the tool you need to do the changes for the big bore http://blog.yamahagenuineparts.com/2010/02/yz450f-gytr-power-tuner.html once you have the gytr tuner you can play with maps and tune the bike anyway you want and get the most out of your bike.

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Airhead- No the bike didn't behave like this prior the filter change. That being said I didn't just change the filter. Pulled the head and sleeve off to do gaskets, replaced spark plug with an iridium one and put a new filter in. New filter is a slightly different design, wavy for more surface area so I dunno if that will make any difference.

I'm 100% sure my bike is timed right and all bolts were torqued correctly as per manual.

Dt502001- thanks for the info, currently waiting to get the bike on a dyno to do a few runs and check afr and whatnot. Might just put up with it until I get it tuned and sorted. I know its running a tad lean as it has slightly white intake valves, obviously has never been remapped since becoming a 500.

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For what it will cost or close to, to have a dyno set up you could buy the Gytr tuner, they are only 300.00 or so, and tune it for every different condition(wet, dry ,sand and different tracks).

They are simple to use store 9 maps you built and liked.You get your bike set up on a dyno and your stuck with that map sure it might make the most power but ,these bikes can make too much power in the wrong rev range and make you slower on lap times and make you work harder to go fast.

Thats why I like the 250's you can ride them fast all the time,in the woods the big bikes have trouble keeping up,the only time a 450 has any advantage is if a open feild is in the course and, generaly most guys have thier bike set up for bottom end power so the advantage is small.

READ THE MAPS and you will see how you can make thew bike work better for you depending on the conditions,, in seconds with the tuner,,,just a matter of plug it in reset the values and your back riding with a bike that makes tons on bottom end torque or tons of top end power the choices are endless.

Quick question did you go with the wiseco head gasket? wondering if it worked with the athina kit.

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Unfortunately im on a slight budget at the moment so shelling out 300 for a tuner is a little out of my price range at the moment. Pretty sure they're only 220 round here anyway. I can get it dynod and tuned for 150 so I think ill go for that option for now and look at a tuner down the track. Plus I want to know the AFR's the bikes producing for peace of mind.

Yeah the wiseco gasket fits perfectly and makes me feel a little more confident in the bike, the less athena the better haha.

Next on the list is picking a new slip on pipe. Thinking fmf. I know the yoshi and akrapovic are the best but they will blow the budget out of the water so ill steer clear of them.

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Dont waist your money,DUDE you can get more power and driveabilty out the tuner than a pipe and 1 dyno run.

The maps can make more power than the pipe and if you put a pipe on after a dyno run you need a new map,with the tuner you can "BUILD" it yourself as simplie as addin 1 number or taking away 1.

a week with it in your hands and you will go why carbs for racing :crazy:

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What do you mean about the carbs for racing?

Just went for a ride then, bike still hard to start, after a few kicks without firing it lets out a rather large backfire. Not sure what this means. Changing a standard plug to iridium wouldn't affect this would it?

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Did some research into pros and cons of iridium plugs. Have heard they cause some starting issues in high performance engines and that oem plugs are the way to go. Shall swap it out tomorrow and see where that takes me

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Update!

Swapped out iridium plug for standard ngk.

No choke, first kick starts every time.

Who would have thought

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