not enough fuel?

[gncc025]

i just got through jetting my yfz and it runs pretty good through out the entire throttle range except when you "gap" on the throttle real fast. it just dies. im thinking its not getting enough fuel but not sure what to change. main,pilot,needle,mixture screw?

heres my setup

main 134
pilot 48
needle 3rd clip
mixture screw 1 turn out

slip on exhaust with airbox lid on and air filter

[wilkin250r]

It sounds like a problem with the accelerator pump.

[cataway]

yeah what he said ^^^^
an O-ring mod could fix it ,backing out of the AP screw could fix it
putting a different AP cover could fix it , putting a smaller numbered LJ could solve the problem.
i thought it odd that your using a 134 MJ seams kinda smallish,is it a DJ ?

[gncc025]

yeah using the 134 main seemed backwards to me too seeing how the stocker is like a 152 but thats what the instructions said to use at my altitude.:confused:
it is a dyno jet

the thing is, before i messed with the jetting it would do fine when you gaped on the throttle it just backfired like crazy on deceleration.

[d3ktrix]

Originally posted by gncc025
yeah using the 134 main seemed backwards to me too seeing how the stocker is like a 152 but thats what the instructions said to use at my altitude.:confused:
it is a dyno jet

the thing is, before i messed with the jetting it would do fine when you gaped on the throttle it just backfired like crazy on deceleration.

The popping on decel is from a leak pilot jet or A/F screw setting.

A 134MJ is wayyy too lean for your bike.
If you using DJ mains try something closer to a 155.
The bog when u snap the throttle is a lean condition just like you said.

[gncc025]

i swapped to a 155 main and it helped but theres still something a little off.

do i need to go down on the pilot to stop the backfire or up? or should i just try messing with the A/F screw first?

[d3ktrix]

Originally posted by gncc025
i swapped to a 155 main and it helped but theres still something a little off.

Whats it doing now?


Originally posted by gncc025
do i need to go down on the pilot to stop the backfire or up? or should i just try messing with the A/F screw first?

How bad is it? If its just a little crackle/pop once in a while u might be able to get it out with the A/F screw. You said u had it 1 turn out, going 2 more turns out could still have quite an affect.
A 48 pilot should be more then enough for ur mods.

[pro-rider46]

well, i didnt totally read all of the post but i did catch that your running a dyno jet jet kit, and keihins jets are way different than djs, i found a conversion chart thanks to zepplin...

Width------Kehein # -- DynoJets # -- Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
0,0400---- 105--------- 102---------- 95,6
0,0410---- 107,5------- 104---------- 97,5
0,0420---- 110--------- 106---------- 99,4
0,0430---- 112,5------- 108--------- 101,3
0,0440---- 115--------- 110--------- 103,1
0,0450---- 117,5------- 112--------- 105,0
0,0460---- 120--------- 114--------- 106,9
0,0470---- 122,5------- 116--------- 108,8
0,0480---- 125--------- 118--------- 110,6
0,0490---- 127,5------- 120--------- 112,5
0,0500---- 130--------- 122--------- 114,4
0,0510---- 132,5------- 124--------- 116,3
0,0520---- 135--------- 126--------- 118,1
0,0530---- 137,5------- 128--------- 120,0
0,0540---- 140--------- 130--------- 121,9
0,0550---- 142,5------- 132--------- 123,8
0,0560---- 145--------- 134--------- 125,6
0,0570---- 147,5------- 136--------- 127,5
0,0580---- 150--------- 138--------- 129,4
0,0590---- 152,5------- 140--------- 131,3
0,0600---- 155--------- 142--------- 133,1
0,0610---- 157,5------- 144--------- 135,0
0,0620---- 160--------- 146--------- 136,9
0,0630---- 162,5------- 148--------- 138,8
0,0640---- 165--------- 150--------- 140,6
0,0650---- 167,5------- 152--------- 142,5
0,0660---- 170--------- 154--------- 144,4
0,0670---- 172,5------- 156--------- 146,3
0,0680---- 175--------- 158--------- 148,1
0,0690---- 177,5------- 160--------- 150,0
0,0700---- 180--------- 162--------- 151,9
0,0710---- 182,5------- 164--------- 153,8
0,0720---- 185--------- 166--------- 155,6
0,0730---- 187,5------- 168--------- 157,5
0,0740---- 190--------- 170--------- 159,4
0,0750---- 192,5------- 172--------- 161,3
0,0760---- 195--------- 174--------- 163,1
0,0770---- 197,5------- 176--------- 165,0
0,0780---- 200--------- 178--------- 166,9
0,0790---- 202,5------- 180--------- 168,8
0,0800---- 205--------- 182--------- 170,6
0,0810---- 207,5------- 184--------- 172,5
0,0820---- 210--------- 186--------- 174,4
0,0830---- 212,5------- 188--------- 176,3
0,0840---- 215--------- 190--------- 178,1
0,0850---- 217,5------- 192--------- 180,0
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5

[d3ktrix]

Ya i use the same chart, its handy.
I dunno why it hasn't been put in a sticky yet.
So many people had head aches with using dyno jets and can't get jetting help because they don't know the differences.

[pro-rider46]

perhaps we should contact a moderator to sticky it. aslo i always hate to hear about people needing help with jetting in the 450r forum, and in the yfz forum they have a sticky with everyones mods and elevation and the jets they use, that wouldn't be a bad idea for in the 450r forum.

[d3ktrix]

Yeah that wouldn't be a bad idea, I think I answer more jetting questions then any other topic. And most of the time it's the same thing over and over again.

Always "I got a pipe and air box lid off, what jets?"
Or "My 06+ bogs when I snap the throttle."

[pro-rider46]

Originally posted by d3ktrix
Yeah that wouldn't be a bad idea, I think I answer more jetting questions then any other topic. And most of the time it's the same thing over and over again.

Always "I got a pipe and air box lid off, what jets?"
Or "My 06+ bogs when I snap the throttle."

haha i know, i contacted wilkin about putting the chart in this section so hopefully it will be put in...

[gncc025]

im gonna try the A/F screw tomorrow. when i was saying it was a little off is when i give it about 1/4 throttle, it has a little hesitation to it.

the jetting sticky in the yfz forum is a little help but from what i see every quad has its own sweet spot. there was a guy with same mods and similar elevation that posted his settings, i tried it but no luck.

thanks for the chart too. i didnt know the diameter of jets varied that much between brands. :huh

[d3ktrix]

Originally posted by gncc025

thanks for the chart too. i didnt know the diameter of jets varied that much between brands. :huh

Ya thats probably why when u tried other peoples jetting it didn't work.

[wilkin250r]

Originally posted by pro-rider46
haha i know, i contacted wilkin about putting the chart in this section so hopefully it will be put in...

The chart already exists in the How to jet your bike (http://www.exriders.com/vbb/showthread.php?s=&threadid=221872&perpage=13&pagenumber=1) thread in the How To section.

Plus, I would hate to create a sticky just for a chart, or a thread that only answers one question. If someone wants to do some research and create a basic guide to jetting (better than the thread in the How To) I would be willing to sticky it here, and also place it in the How To section. But I would such a thread to answer lots of questions, not just one or two.