no matter what i try, i get a bog on quick wot

25 replies to this topic
  • bluebreadtruck

Posted September 27, 2008 - 07:34 AM


need some help guys. I installed the bk mod, and timed it to around 1 sec. or a bit less

I always get a bog/backfire when i try to do a quick wot, driving or on stand.

I tried all settings from no screw to all the way in...same basic bog. I also tried the JD thin o ring...same thing.

if i give it gas when riding it bogs for a sec, then has always did this, need some help

running needle 2.5 turns out, 42 idle, 170 main sea level, jd blue needle 3rd notch down....same issue at 4 notches down

PLEASE HELP!!! i just want to ride this thing

  • maxtherat

Posted September 27, 2008 - 09:39 AM


Try using a bowl with a leak jet or the adjustable leak jet products made, Merge or R&D. I'm pretty sure all of these are avaliable from JD. Some people have some sort of bog and always will. My guess is your bog is from a rich condition not a lean condition and a LJ will help with that. You probably don't want to go to the 4th notch on the blue needle, too rich for that bike. Stay between blue 3rd or red 4th.

  • Thumper_Bloke

Posted September 27, 2008 - 12:26 PM


I stretched the AP spring and also ground down the pivot on the bowl diaphram. I didn't spend big bucks on fancy bowls.

  • bluebreadtruck

Posted September 27, 2008 - 01:38 PM


Thanks for the help.

With this BK mod, i am able to go from no accell pump movement to stock...which was about 4+ secs spray

I wish there was something else im missing, but throught that adjustment, I always get a backfire, then a bog and sometimes it dies on a quick throttle stab.

Now, i also tried the o-ring mod, and it was no help.

this thing runs GREAT otherwise....

anyone else have ideas? what about the accell diaphram, what will that do if i grind it down?

  • WR_Dave

Posted September 27, 2008 - 02:05 PM


You may want to try a Boyesen quickshot accelerator pump cover. The problem is that the stock AP cover has the pilot shot holes too far down in the cover and it will inject a shot of air before it gets to the fuel that you really need at that point in time. The air that is injected first delays the adding of the fuel and causes the bog. Jetting and o-rings will get you close, but if it still persists then you will need the Quickshot AP cover. WR Dave.

  • MountainMax

Posted September 27, 2008 - 03:11 PM


I have the pump cover on mine, and I still get stall/bog on quick throttle also, tried everything with jetting, im thinking it might just be a 4 stroke thing....

  • WR_Dave

Posted September 28, 2008 - 07:33 AM


I found that my '07 WR is much more sensitive to needle adjustments and I used the '06 YZ needle and moved the clip position around a bit and now the bike will throw you out the back door if you unceremoniously whack the throttle open. I used the Boyesen pump cover, good jetting and needle position to eliminate all bogging on my engine. Make sure you ACV valve and any air bleeds aren't plugged or not functioning properly. WR Dave

  • 02WR426Cali

Posted September 28, 2008 - 07:42 AM


It could also be that the WR's have a heavy flywheel unlike the YZ's. So they aren't ever going to be as snappy. Just a thought

  • bluebreadtruck

Posted September 28, 2008 - 08:03 AM


thanks guys.... today i was riding, and it is downright dangerous on trails, it bogs when you want to get the front up over a puddle, root or whoop....

I found that by adjusting the bk screw, i am able to eliminate most of the bog from 1/2 to wot.

but it still backfires and bogs out on a fast wot from a lower rpm...

im going to try my jd red needle (leaner down low) and see if that helps!

  • tweav

Posted September 28, 2008 - 12:38 PM


I put a rd powerbowl on my wr . I adjusted the needle and my bog totally went away.

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  • MountainMax

Posted September 28, 2008 - 04:38 PM


'Totally' ? you mean you cant get it to bog even if you tried? that would be awesome, I would buy a bowl if that fixed mine

  • bluebreadtruck

Posted September 28, 2008 - 04:39 PM


thanks for the help guys. I solved the problem!!!!

I tried the JD red needle at 3 notches down, and it basically would not even stay running, poping then died.

So, i put the blue needle back in at 4 down, and started messing around with the accel pump timing screw..... i ended up with another 1/2 turn in from where it was, that and messing with the bk screw for around a 1 sec spray seems to cured the problem...

sitting in neutral, it i go from idle to wot very fast it will pop, but then catch itself and not die....before it would pop/bog then if i held teh throttle, die.

anyhow, i wasent impressed and dident think i fixed the problem till i took it for a ride

I shifted into 2nd and stabbed the throttle, and i'll be damned if it dident rip that front tire off the ground and screw!!!

thanks again!

  • maxtherat

Posted September 28, 2008 - 07:00 PM


Try the 3rd clip on blue needle, it may even get better. Again, I would recommend doing something with a LJ.

  • tweav

Posted September 29, 2008 - 03:18 AM


'Totally' ? you mean you cant get it to bog even if you tried? that would be awesome, I would buy a bowl if that fixed mine

If I try to take off if like third gear it is a bit boggy , but that is a gearing issue. If I crack on the throttle at any rpm it just takes off crisp , as it should . I think the power bowl was the best mod I've done to my bike as far as power . It ran like crap before that was on. And I was tired of messing with the carb . it's a pain to work on , there is no room on these 07's

  • bluebreadtruck

Posted September 29, 2008 - 04:35 AM


i'll try the 3rd clip and report back

  • bluebreadtruck

Posted September 29, 2008 - 06:32 PM


i havent touched any of my settings, but when it got hot after a 1hr ride, it started getting the bog back a bit down low....any ideas on which way i should shoot with the adjustments?

  • William1

Posted September 30, 2008 - 04:25 AM


What size leak jet do you have in?

  • bluebreadtruck

Posted September 30, 2008 - 06:00 AM


no leak jet. i think all the 400's did not have them

  • sausage boy

Posted September 30, 2008 - 04:47 PM


sounds like it could be your valves, when was the last time you checked them? i had a similar problem, and combined with the Rekluse Zstart clutch it made my terrible to ride.

  • bluebreadtruck

Posted October 01, 2008 - 02:34 AM


thanks, i just pulled it down, and my valves were a little tight, but whithin specs


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