On deceleration bike pops n stops

Well i ride a wr 426 and as the title says pops n stops on deceleration, not all the time and it doesn't matter if its snapped shut or closed gradually, occasionally when coming to rest it pops out the air box and stops.


Carb, jets, float bowl height.

Air intake rubbers.

Exhaust seal, pipe

Cut off switch, for shorting.

Plug, gap set, plug lead cleaned.

Been into my local dealer and the above was suggested.

Read through the manual and i can't figure out what the problem is, need some help please.

Other than that the bike runs strong and true.

Can be a bit of a pain to start from hot but hopefully managed to sort that out.

Think its intake:- main jet 165, main air jet 200, needle jet OBDQR clip 5, starter jet 65, Pilot jet 42, Pilot air jet 75, Fuel screw 1.5 turns out.

WR timed, Sea level to around 1000' Not much elevation in southern England.

Thanks in advance, cheer Rich.

Sounds lean.....or your valves may be having an issue.

I would say a little lean, open your fuel screw a little more might help, or a header leak can cause this!

- worn out slide

- leaking slide vacuum plate

- hot start plunger stuck or leaking

- clogged carb vent tube

Hi guys, thanks for the input, been in to the dealer again today to have another word.

Spoke to another guy and he told me to check the intake rubbber between carb and engine for splits/perished cause of when it pops it blows back out the air box.

cleaned out vent tubes.

Hot start plunger working perfectly.

Stripped the head on the carb slide, Grrrrrrrr........Gotta sort that out now.

Had the pipe of to check for leak, ordered a new seal.

Taking the seal in tomorrow to see what the dealer has to say.

I'm just guessing here, but its not much of an investment: try a 170 MJ, 44 PJ, and stay on clip 5.

Is your exhaust stock, or has it been modded? Any other mods done? For a better diagnosis, we need more info.

I"l second that. Not sure how old your gas is. Had a similiar problem that fresh gas fixed......RG

Stock exhaust, grey wire cut.

Fuel doesn't stay in the tank long enough to go off, having to blip throttle on deceleration all the time to keep engine running cause if you don't keep the revs up it could pop n stop.

Does tick over fine. Warm it up and blip the throttle a few times and it seems it will stop after a few blips on deceleration.

Read though the manual and by the sounds of it its pretty much stock.

Rode it for 3 hours on sunday and it stop on me six times.

cheers Rich.

Anything else specific just ask, cause my heads swimming with things.

Been into the dealer again and spoke to a mechanic, with the bike back firing out the air box and stopping he seems to think that i have a valve hanging open.

Been told to whip the head off and bring it in for them to look out valves.

Looks like i'm doing a top end rebuild early than i thought.

Seems i'll be out road riding while my buddies are roosting.

does yours pop and stop when you pull the clutch in at high speed and start to brake? does it do it at idle if you leave it sit after you have rode for a while?

Its it left to idle its fine but if you blip the throttle a couple of times, as the revs are coming down it will back fire out the air box and stop.

On the whole the bike runs great, but literally as you are pulling up that last little bit before you stop if your not blipping the throttle it could back fire and stop.

So cause on deceleration i'm blipping my MPG has gone out the window and i'm finding that i'm running out of gas way before i used to.

mine kinda pops and stops if you dont give it a little gas if you are slowing down from high speeds. i think this is normal though. i had other bikes that needed a little twist of the throttle to keep it running while slowing down with the clutch in. i only notice this on the road though. it may be beacause of how the carbs are designed on dirt bikes. hope it isnt a valve problem,you have got me worried about my bike now.

For the price of a gasket set, the heads of and its going in tuesday for them to have a look at it.

Bit extreme i know, but i don't want the engine to bang on me.

So I would rather sort it now than later.

i have a few gaskets and a timming chain i ordered i need to install. my yz426f blew up because the timming skipped and a valve broke when it hit the piston. i just got a 2001 wr426f now and im going to replace the timming chain for peace of mind. i heard it is a good idea to replace them every 50hrs or so of ride time. never have replaced one but it shouldnt be too hard im going to check my valve clearences while the valve covers off as well. it was going to cost to much to rebuild my yz426f so i bought a wr426f instead for less than the cost of complete rebuild.

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