I'm getting weary

I've searched and searched.I have a 00 WR400

Ca. model.It has yz timing and a White Bros. E series straight headpipe.For jetting I'm going to try the EKN needle #48 pilot #170 main and #100 air jet.I ride 2000-5000 ft.Is this a good combo?My main problem is hesitation when blipping the throttle.I have no confidence when approaching a jump to blip it as I hit the jump.

[ November 01, 2001: Message edited by: Rick Wall ]

Sounds about right to me. Go with a EKN#4 if no bk mod. Although some people might find this rich. You are on the right track for an initial set up. Also limit the fuel screw to 1 turn.


that MAJ isa wrong, sorry mate.

get a 180MAJ and a 160 MAJ and watch the bike rev out. then you can come down on your MJ by at least 10.

testing is believing.


Thanks for the help guys.

Taffy,isn't kind of six of one half a dozen of the other to raise the MAJ and lower the main fuel jet or vise versa?


earlier in the spring i put some querries up that we needed to lean off the top end. that the MAJ's needed to be BIGGER to lean it off.

this made sense after we read a keihin write up by patrick burns-i hope you've read it.

about three riders did the testing and said that by leaving the MAJ on the workshop bench the hole was 2.3mm or a #230 MAJ. that it was also better. my gearbox was fragged at the time.

i did the same without testing it and followed along with a 235MAJ. i was so certain that "andy from oz", JD and clark were right that i drilled the hole out to 3mm and then some MAJ's to 2.35mm and 2.5mm.

i did a long days testing on the 7th october. in my bag i had a 180, 200, 235 and 250MAJ. the testing was extensive, i honestly never went there to prove anyone wrong. how could i, i'd already done 2 oversize jets (235 + 250) and i was commited to the cause.

please read jetting Q's from october 7th.

what happens?

well at a certain revs the bike stops taking in more air per cycle,it doesn't have time. that's maximum torque and after this although revs rise it's off of slightly less mixture actually getting in.

the pulses of stop start, stop start are now so close that the fuel finds it too easy to come up so we get a rich mixture for say the last 2,000 revs.

to lean it off you introduce air via the MAJ.

i like you perhaps had jetted my bike for it to go flat out. no problem here. but that same MJ is there not just for 11,000 revs but also don't forget, max torque at 8-9,000 revs.

so if we have too much air coming in at 11,000 we have to jet up to get the mixture correct so we can rev out. in the meantime back at the ranch-max torque-we are now overjetted.

in otherwords we either got the MJ right for 8-9,000 or 11,000 and it's your choice.

from jetting Q's you'll see that i've gone to 160MAJ a week ago and wow! big difference.

i was happy with a 162MJ but now i've richened the last few revs by reducing the MAJ and the air it brings with it, i can now jet down right across the board from say 8,000 revs plus. thus the 155MJ (the smallest i had) this week and it's subsequent improvement.

as i've indicated before the MJ is responsible down to very low revs. so much so that in yesterday's tests, after dropping the MJ from 160 to 155 i had to raise the needle 1/2 a clip.

i hope this makes sense, if not i've tried my best!!!!



I had the opportunity to run a race with a long paved straight-away. With stock gearing, the bike pulled redline with absolutley no problem. It actually felt like it could have have pulled much higher gearing as well. Because top speed was reached very quickly. I knew things were working well, because I was closing on YZ426's by about what seemed like about 5-8mph (just a guess), but a pretty decent closing speed anyway.

So as for the upper end not working, or being wrong on my bike I have to disagree. Maybe with a free flowing exhaust at see level, larger MAJ's and MJ's work better together than with your settings of quieter exhaust and altitude?

What does top speed in top gear on pavement work out to anyway? Maybe about 90mph?

no john, you can't tell the difference.


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