i know but i tried jetting my quad and it backfires please help

[quader400]

alright i have a 400ex with a lrd full system and a stock carb bored to 38 or 39. my main jet is 170 my i lowered the clip one and i left the pilot at what its at. every time im on the gas and let go it back fires. any suggestions. im going to try and play around with it a little more but what does backfiring mean? any help would be appriciated thank you.

[44oEX]

It's your set srew. Play with that . If that doesn't work change the pilot jet to a 42. That sould clear the problem.

[Colby@C&DRacing]

just put the 42 pilot in the carb and be done with it.:)

[cals400ex]

your lean on your fuel skrew. you can try to turn it out a little bit or just get a new pilot. my built engine is acting wierd. actually, many others told me theirs does this too. i have a 42 pilot jet in and its pretty rich at idle. i have to leave my fuel skrew at only 1 turn out to get a air/fuel ratio at idle. i may go down to a 40 if i have any other problems.

[whatwasthat]

It may also be a leak in your exhaust system....when you just start it up and when its COLD, hold your hand over the end and listen for any "puffing" sounds

[pnut420]

Originally posted by whatwasthat
It may also be a leak in your exhaust system....when you just start it up and when its COLD, hold your hand over the end and listen for any "puffing" sounds

Its not the exhaust leaking, I was running no header gasket and it didnt back fire, he is running lean down low. And I wouldnt hold your hand over the end of the exhaust:eek2: . Basically what it happening is you are going from posssibly running rich in the mid to top, but when you let off you go into your low fairly quick and it starts to get lean from the pilot screw. Up it to a 42. My brothers was having this problem and I kept wanting to go down on the pilot, but then my buddy told me to go up 2 sizes and it deosnt backfire anymore and starts way easier.

[quader400]

sorry one more thing i looked and there already is a 42 pilot in there. so should i get an even bigger pilot or what should i do. and i changed the maind to a 165.

[quader400]

what is the set screw. i played around with the one screw that is behind the idle screw and now my quad idles really really high and i dont know what to do. im going to take it in soon if i dont figure it out so any help would be greatly appriciated. thank you.

[pnut420]

The 42 pilot should be fine, I has to up my pilt 2 sizes when winter cam around, but a 42 should be plenty for you, I dont have stock carb so I dont know where the fuel screw is, but I would back the fuel screw about 1/2 turn or so.

[cals400ex]

i am betting you just fouled the plug. try turning the fuel skrew 2 turns out from lightly seated. take the plug off and clean it or put a new one in. make sure your fuel is on and just hit the start button without hitting the gas.

[quader400]

my quad starts fine but idles really high. im taking it in tomorrow im just pissed cause i have never had to take it in ive always done all my work by my self so whatever thanks anyways.

[cals400ex]

can you turn your idle skrew down some?? or you could bring it over and i will take a look at it. i live in illinois too. :D

[quader400]

i took it in today. they are jetting it for me and welding my frame so im happy. hey cals400 do you ride at byron ever?

[cals400ex]

no i don't ride their. i am not sure where it is at?? let me know what jets they put in your bike. i just want to compare what they do vs. what i do.