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Discussion Starter · #1 ·
06 YFZ with the Athena 480, stock intake with the pro form intake with GYTR filter, no lid or box (most of it was cut away by the previous owner), GYTR Oval slip on exhaust with the end cap and sparky removed. The quad is back firing and popping on decal pretty bad, like a pack of fire crackers going off. This all started after I had to tear down the top end to replace the base gasket and at the same time I did the cam mod. I couldn’t get the bike to start and idle right and the popping started. I jetted the carb all over the place and with no luck so I put the cam back and life was good again with the exception of the decal popping that will pop all the way from high rpm down to almost idle.



Right now I currently have it at 170 main, 48 pilot, 3 clip, 2.5 out on the a/f. I tried going to a 45p and it made it worse and the quad was hard to start and didn’t want to idle and would even stall when coming to a stop. I went to a 50 pilot, no luck, then changed the clip to 4, no luck, I have moved the a/f in as far as 1.5 and as far out as 3.5 no luck. I have tore the carb down twice and cleaned it the best I can, the next step for it would be to soak it in acid.



I have checked the boots over and over for air leaks, and none found. I put a new exhaust donut (from cometic) when I did the gaskets and I have checked the torque on the exhaust nuts 3 times now and I don’t see or hear any leaks around the head pipe or the slip-on donut.



What else would cause this?
 

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Discussion Starter · #3 ·
I have checked for both leaks and can not find any and the muffler is almost brand new, it has one dune trip and maybe 3 hours of run time.
 

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try turning your fuel mixture screw in a little that fixed it for me, but mine was not as bad as yours it sounds like
 

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its running to rich
 

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I have a very similar setup (480 athena), though I do still have the airbox (no lid and w/ a pro flow filter), and have always had popping on decel. Though it sounds like I may be running even richer then you, I believe my main is a 180. I've checked my plug often, and it never looks wet, just a nice brown. I don't know, but I can tell you it runs great other then the decel pops.

Never thought about checking the pipe packing...is that really something that can cause this?
 

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dippy doodle
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If it is backfiring on the decel it is running to lean. I only have exhaust and filter and I am running a bigger main than you are. I am running a 175 main, 45 pilot, 3rd clip on ncvq needle and 2 3/4 turns on a/f screw. It sounds like you need to go bigger on the main and maybe mess with the clip.
 

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i am a beginner at tuning but i have learned some thing so far.

i believe the first thing u should do is make sure throttle cable isnt 2 tight make sure there is 2-4mm of slack at thumb throttle.

then i would set idle to 1900 rpm.....kinda guess by ear unless u have a tach.

next move the a/f mixture screw in or out. while going in turn in until the idle rises. then go out until it wants to die. go somewhere in the middle. that sets the basics up.

now go for a ride. 1/4-3/4 throttle is your needle. try going up 1 see if bogs, or pops. then go down one. you'll know when your going in right direction.


last but not least aftr your needel feels close or better. u change your main jet. go from lets say for example a 170-175. see the difference. then go from 170-165. youll know depending on which one feels better. eliminates bog or popping to which direction u go. if its up for example. your at 175. if it feels to rich you know u gotta be between 170-175 .


i dunno im no pro but i do know its 1 thing at a time and i believe tunning goes in this order. hope it helped good luck.
 

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QUOTE (YFZRider69 @ Feb 12 2009, 09:53 PM) index.php?act=findpost&pid=745930
If it is backfiring on the decel it is running to lean. I only have exhaust and filter and I am running a bigger main than you are. I am running a 175 main, 45 pilot, 3rd clip on ncvq needle and 2 3/4 turns on a/f screw. It sounds like you need to go bigger on the main and maybe mess with the clip.[/b]
your main isnt going to have anything to do with popping on decel.

That is going to be your pilot circuit
 

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dippy doodle
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QUOTE (Stix1107 @ Feb 12 2009, 08:23 PM) index.php?act=findpost&pid=745972
your main isnt going to have anything to do with popping on decel.

That is going to be your pilot circuit[/b]

I didn't say that it was specifically his main. I just said it sounded like he needed to go bigger cause of the stuff he has done. He is running a smaller main than me and he has a bb kit. I also said it sounded like he needed to mess with the needle. If it's popping on decel it probably isn't the pilot since that only controls up to around 1/4 throttle. Just throwing out some suggestions, ya know.
 

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i had the same problem wit my 480 and it never ran as good as my stock bore and i had my stock bore dialed in perfect 172main 50p bottom clip on the needle never poped on decel sounded perfect, on my 480 i have a 50p 182main is what got rid of most of my popping was my i put two plastic shims under my needle and second from the bottom clip it still pops but barely still tuneing as i go after i did that it woke it up big time tons more power also iam running yz timeing and web cams



QUOTE (YFZRider69 @ Feb 12 2009, 10:20 PM) index.php?act=findpost&pid=746016
I didn't say that it was specifically his main. I just said it sounded like he needed to go bigger cause of the stuff he has done. He is running a smaller main than me and he has a bb kit. I also said it sounded like he needed to mess with the needle. If it's popping on decel it probably isn't the pilot since that only controls up to around 1/4 throttle. Just throwing out some suggestions, ya know.[/b]
 

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Discussion Starter · #12 ·
Since i wrote this, i have gone as high as 190 on the main. I did the a/f screw and have it where it seems to be the best. i also replaced the exhaust with a Dasa pipe and a Velocity intake with a K&N filter (not because of this problem, but because i wanted those mods to go along with the big bore). The decel popping and back firing is still there and in fact when in neutral and you rev it up, i am getting like 1 and half foot of flames coming out of the pipe as it decels.
 
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