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Discussion Starter #1
hi all

im currently running my 250 with a big gun evo r full system exhaust, gytr air filter and adaptor plate with a standard air box with lid on , I have gytr jets installed as per the instructions with the jets, (what Yamaha recommend) and the fuel screw out 2 turns and when the engine is hot I stab the throttle it will stumble and bog at low end I have messed around with the fuel screw endlessly but it seems like it is either overfuelling or underfuelling when I stab the throttle quickly and then suddenly picks up , it is annoying because when I need to pop a wheelie to bring the front end up over whoops and obstacles etc it just dies then picks up when I don't need it , I am thinking about lowering the needle to give it less fuel, just wondered what jetting setups others are using , pilot, main,needle setting,fuel screw setting etc any comments welcome thanks :):):)
 

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The jet kit I used was an actual Dynojet part number Q435. Excellent instructions. I have a GYTR intake without the lid and the DMC duals. Instructions recommended using almost the largest main jet. So far, starts easy and runs very strong for just the few upgrades. The kit comes with a new needle as well as a lot of main jets. Comes with a thin washer to make minor adjustments to the needle. Here is the LINK to the instructions to the Dynojet kit.
 

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Discussion Starter #3
cheers glene
ive installed the gytr jet kit with the mikuni sized jets and comes with a new needle with an adjustable e clip and 4 main jets, it has the 2nd smallest main jet installed and im going to try almost the largest main jet (mikuni/gytr size 137.5) and if it still doesn't run right I will install the biggest main jet (140) thanks
 
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