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2010 yzf 250

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Hello everybody,

I'd like to know do you guys have had any problems with jetting this new carb? That carb is very tricky and very difficult to find right settings. This is EU model. Any problems with US models? I am asking this here because no answers from jetting forum.

Thanks:thumbsup:

Jusa

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I have a 2010 us here i have only had it on the dyno for base line power but i did check the AF and it was spot on the bike would also take throttle in high gear from around 4000 rpm which is a good indicator of correct jets.the engine is being developed curently .

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My spark plug is allways black and sooty. It seems that carb settings are too rich. Not very good throttle response and it makes a little bang bang in exhaust system

std settings

main jet 180 / current 175

pilot jet 42 / 42

needle NHKR 4. / NFLQ 6.

mixture screw 1.75 / 1.75

leak jet 110 / 110

Tested four different needles in different positions. Jets 178 180 182 /42 45are tested with many combos. Current settings works best but not perfect.

Also raised motor tamperatures > works better but spark plug is still sooty.

I have heard that this is very common problem here in Finland.

Thanks in advance

Jusa

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hi jusa i am from north italy, same eu bike.

It sounds very strange , because here now we have cold temperatures and my bike ( everything STD also min jet 42 ) with 42 min jet was running poor .

i am using a 48 , and it is a little too rich , only once i found my sparkle black and wet , probably a 45 would be the best .

what sounds strange is that you are lean ( 42 ) with cold and you see a black spark ?

could be another problem ? something from cdi ?

ciao

corradok525

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Many new 250 yzf owner struggles with these same problems. Temperature 0- -5 celsius. Std settings didn't work at all. I am thinking could the wrong float high cause this kind of problem (fuel level too high) std suppose to be 8mm. Haven't measured it yet. I think leak jet is too big and this causes that poor response when quick throttle open. I will change it to 90 or even to 70. But don't know yet what is the problem with the other settings.

After market air filter helped a little and so did dice AP cover and iridium spark plug.

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hi jusa i am from north italy, same eu bike.

It sounds very strange , because here now we have cold temperatures and my bike ( everything STD also min jet 42 ) with 42 min jet was running poor .

i am using a 48 , and it is a little too rich , only once i found my sparkle black and wet , probably a 45 would be the best .

what sounds strange is that you are lean ( 42 ) with cold and you see a black spark ?

could be another problem ? something from cdi ?

ciao

corradok525

Do you run with the std exhaust system?

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Hello,

No problems over here but we don´t have the temperature you got over there.

Since my 08 YZ 250 F and also my 09 EU models the bikes came both too rich but a simple decrease in the MJ was enough to make them work ok.

Did you tried a smaller MJ them a 175?

Talking about spark plugs, for your temperature what exact model are you using?

Personally i don´t like Iridium plugs, never liked them.

Original exhaust is a bit restrictive in that bike and does not help for having a well balanced bike, you have it?

Btw the YZ 250 F 2010 is the bike that an aftermarket exhaust will have more gains in all 2010 mx models..

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Spark plug is NGK CR8EIX. And main jet is 175. Maybe I will drop the main jet to 172.

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Spark plug is NGK CR8EIX. And main jet is 175. Maybe I will drop the main jet to 172.

What is your temp and altitude there? The 110 leak jet seems rediculously big too. What is the throttle response all the way through the rpm range? Does it bog off idle? does it rev out fine on the top end? Answering these questions will help us determine what needs to be changed where. Basically the leak jet being part of your accelerator pump circuit is going to effect the off idle response, next comes in the pilot jet (just off idle to 1/3rd throttle), then the needle (about 1/2 throttle to 3/4), and lastly the main jet 3/4 throttle to wide open. Good sparkplug to run by the way thats the only one I use.

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I was riding today and temperature was -6 celsius and 100 above the sea level. Tested 172 main jet and it was much better than 175, 178, 180 or 182.

Now the machine revs fine throught the rpm range, but I haven't checked the spark plug colour yet. Now the problem is when throttle is opened quickly, it bogs. That indicates the leak jet is too big as you said. I will try 90-70 jets near future.

This is weird and first time to me to go leaner on carb settings. My friend told me to change the std exhaust system to HGS system. Difference is like day and night.

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I was riding today and temperature was -6 celsius and 100 above the sea level. Tested 172 main jet and it was much better than 175, 178, 180 or 182.

Now the machine revs fine throught the rpm range, but I haven't checked the spark plug colour yet. Now the problem is when throttle is opened quickly, it bogs. That indicates the leak jet is too big as you said. I will try 90-70 jets near future.

This is weird and first time to me to go leaner on carb settings. My friend told me to change the std exhaust system to HGS system. Difference is like day and night.

I am blown away that you have to run a 172 main jet. That sounds wayyy to lean to me at that temp. The coldest I have jetted for was 0 celcius and We had to run a 185 main jet needle at clip position 4 from the top a #46 pilot jet and a #55 leak jet. The only time I have ever had to run a 172 was when it was summer time the elevation was about 500 feet above sea level and the temp was 35 celcius. This was all with the stock exhaust system.

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Yes that is very weird but spark plug is allways sooty and black after full throttle run.

Have you ever tried two stroke air filter guide (without back fire cover) any help with that?

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Yes that is very weird but spark plug is allways sooty and black after full throttle run.

Have you ever tried two stroke air filter guide (without back fire cover) any help with that?

No I havent. I dont like removing the backfire screen. I have actually witnessed a couple of bikes actually catch fire from a back fire and not having that screen in. On the spark plug that is really strange. What type of fuel do you use?

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Also covered one of the radiators almost fully to achieve right temperatures.

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Put leak jett #70 in and it will be allot better! 110 is way to big, its the EU standard size.

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