03 wr450 missing/skipping/sputtering.

[802wrRider]

am i right though in believing that this is a rich mixture issue?

[MANIAC998]

If I remember correctly, doesn't the DynoJet kit have you drill out the air passageway or something in the carb? If this is so, then I don't believe you can go back to any other jetting. I think your stuck with the DynoJet kit. If you still have the instructions, can you look it up and tell me if that's the case or not? As my memory is suspect at times!!!

Maniac

[miweber929]

am i right though in believing that this is a rich mixture issue?

From the sound of the plug, yes. And listen to Maniac's statement as well, one of the reasons I don't like DynoJets kits is their drilling the carbs thing.

I know for the VFR street bikes they had you drill the slides, and I've seen and heard them do that a lot. You can silicone the hole closed but it's still not "correct" once you've done the change.

But it's either rich mixture or oil getting into the plug if it's black.

[802wrRider]

i know for sure i didnt drill anything out of in carb. must be dynojet changed there specs because mine didnt say anything about it at all. i would have put everything back in the box and sent it back if they asked me to do that. haha. anyway, im going back to stock jetting tonight so we will see if that fixes things. if so im just going to figure out what jets i need and order them from my local shop.

[802wrRider]

ok so i switched it back over to stock jetting and it runs fine minus the popping on decel and it definitely doesnt have the power it did with the jet kit. the way it is set up now is a 160 main, needle w/ clip on position 5 and what ever else is standard jetting. im thinking my best bet is to go to the dealer and order a few jets and go with it. popping means to lean? so bigger main jet?

[miweber929]

ok so i switched it back over to stock jetting and it runs fine minus the popping on decel and it definitely doesnt have the power it did with the jet kit. the way it is set up now is a 160 main, needle w/ clip on position 5 and what ever else is standard jetting. im thinking my best bet is to go to the dealer and order a few jets and go with it. popping means to lean? so bigger main jet?

Do some searching, there are quite a few jetting charts around here that should tell you what to do and how for your elevation and area.

It's going to be far more than just a main jet, but yeah, you sound lean.

Mike

[802wrRider]

what part of the jetting spectrum needs to be richened when you have popping on decel? and i knew that the main was for WOT but for some reason i combined high rpms with WOT (which is obviously not always the case) and added in the popping to get the end result of needing a bigger main jet. so what part of the jetting system needs to change. my guess would be a pilot jet. am i correct?

[Rocky739]

what part of the jetting spectrum needs to be richened when you have popping on decel? and i knew that the main was for WOT but for some reason i combined high rpms with WOT (which is obviously not always the case) and added in the popping to get the end result of needing a bigger main jet. so what part of the jetting system needs to change. my guess would be a pilot jet. am i correct?

Correct, the pilot jet is the circuit that feeds the engine when the throttle is closed. If too much fuel is fed in then you get poping. The WR tried to get around this with a air cut valve (valve to add more air when throttle is closed to lean the pilot during decel) but it just doesnt work that well. I have mine deactivated (turn diaphram backwards) its a two minute job and completly reversible if you dont like it.

With the correct pilot and fuel screw dialed in I think its probably the least poping fourstroke I've ever ridden. Nice and quiet to keep the neighbors happy!

[802wrRider]

ok so one of my buddy's told me to try turning out the fuel/air screw and see if it go better. so not knowing any better i did that and at three and a half turns out the popping started to get quieter. im not happy about having the fuel screw out that far and dont believe it is the right way to fix this. so i went through the process of adjusting the fuel screw as if the carb were already jetted correctly. with the fuel screw all the way in, the bike slowly starts to die and is happy idling at about 2-2 1/4 turns out. which if im not mistaken means that the pilot jet is the correct size? another buddy of mine that i have seemed to get better info from told me that popping on decel, more so than not, comes from tight or out of spec valves. he said its not rare for it to be a carburation problem but more likely a valve issue. does this sound logical. i havent had my valves checked since i had the engine rebuilt last year so i know its probably due. and i have never adjusted them my self so i feel now is a good time to learn.

[Rocky739]

True, never a bad idea to check the valves, but that far out on fuel screw means you are too lean on pilot as the ideal range is more in the 1.5 turn range, I would go up one more size. Also check with a warm engine, slowly open throttle past 1/8th throttle and see if engine rev up freely or does it seem "tight" ie; struggles to pick up RPM. My bet is it will.. all this means pilot is too small. One size pilot on my bike made a huge difference (from 45 to a 48) header does not glow red now and starting improved drastically.

[802wrRider]

SWEET!!! those are all things that are going on that i dont like right now. i think a 48 pilot and a valve adjustment and ill be cherry. and maybe bump up to a slightly larger main just to keep things running a little cooler on the road. you guys are awesome. thanks again!