WR400 STILL fouling plugs!!!!!

[wrguy]

'00 WR400

low hours

yz timed

lid removed

grey wire mod

wb e series 6-7 discs and head pipe

mj 170

pj 45

stock maj and paj

blue ndle #3

f screw ~2 turns out

1500-5000'

60-80 degrees

washington state

50-80% humidity

mainly tight woods

fouling plugs every other ride (black as can be)

tried a 165 mj and 42 pj, needle up to #2 from top - still rich

do i go to a 160mj and 40pj - seems real lean

came with a OBDRS needle

haven't done the BK mod - timing stock - probably just over 1 sec.

what next? seems to be in the pilot circuit, will BK mod help - bog isn't to bad

float level? valves?

haven't done the full throttle mj plug check

has a hanging idle when hot, dies after hard runs, pops, bogs, sputters after plug starts to foul

weak ignition? tired a cr9e - didn't help

runs like a crazy ape when plug is new, throttle transitions great

any suggestions? don't want to give it to the shop $$$

[Wayward Son]

fouls plugs when you try to start it the first time of the day?or fouls plugs and uits running when your riding it?

how does the bike run?idle ok?idle react to fuel screw changes?

[wrguy]

never fouls plugs when on the trail. just runs sporadically - will load up and backfire, cleans out after a while, then backfires and misses. second cold start on a new plug will usually bog and backfire, run like crap. after a few more starts will just foul the plug. wet and black. i only use the choke when needed and for a few seconds.

fresh plug: runs awesome when on the throttle, slight bog, rough idle and inconsistent running from closed to 1/4 throttle in neutral. doesn't pur unless at 1/2 to full throttle. fms doesn't seem to tame the rough idle.

i can always get back to the truck though. after jd needles, tried blue on 2nd and 3rd clip - red on 2nd and 3rd clip (hanging comes around and it will usually die when running hard and stopping.

what gives? thanks for your time!

[Wayward Son]

with the 40 pilot jet can you get a consistent idle that reacts to the fuel screw?

is the bike using oil?

[642MX]

When is the last time you checked your valves?? Start there.

What kind of fuel are you using? With high prices at the pump, 87 octane is the only fuel thats selling, most of the 92 & 93 octanes are going bad in the ground before you ever pump it.

Have you checked the obvious? clamps, hoses, vent lines, AIR FILTER?

Good luck man, keep us posted.

[ALM71]

Sound like my '98 WR400. Very similar setup, except I have an FMF Q, but it runs AWESOME. If I get it started, it will run forever on a plug. If it fouls a plug, it happens when I'm trying to start it. I learned that what I do with the accelerator pump and the choke makes a big difference. I think I've determined if I don't use the choke, and use a couple squirts with the accelerator pump, I have better luck. I've tried everything on jetting and no luck. I've learned to live with it.

[James_Dean]

float level? valves?

haven't done the full throttle mj plug check

has a hanging idle when hot, dies after hard runs, pops, bogs, sputters after plug starts to foul

Check the float level.

The hanging idle is probably lean, try red #4 position and fuel screw at 2 turns. The idle shouldn't hang, turn the fuel screw out if it does, and check for air leaks.

If you ever had the carb slide out, make sure the square end of the thin plate is installed downwards.

Does the bike smoke or use motor oil?

The 2000 WR400 does not have a leak jet. Make sure you don't twist the throttle too much and flood it while starting. The pump pushes LOTS of fuel.

James