Why does it poooooffffff when I shut it off

[motordude]

Any ideas why my 85 250es poooffffffsssss with a tiny backfire/fart to follow everytime I shut her off. Runs great, pulls strong, idles perfect, starts right up but after a decent ride, I get a nice little bang. Nothing drastically loud but? No black smoke either.:wondering

[dcreel]

Is your air filter clean?

[dougspcs]

As you shut off the ignition the Unburned fuel accumulates in the hot muffler which is sufficiently hot to cause the vaporized fuel to ignite..

All my 250s do it also..

[Thorpe]

I have been told, thats a tell-tale of valves in need of adjustment... (i cannot prove what I have been told, but my ES does it too)

[Jason125m]

X2 what Doug said. Both my 250's do that.

[El Camexican]

Any ideas why my 85 250es poooffffffsssss with a tiny backfire/fart to follow everytime I shut her off. Runs great, pulls strong, idles perfect, starts right up but after a decent ride, I get a nice little bang. Nothing drastically loud but? No black smoke either.:wondering

It MIGHT be that after you shut the ignition off the piston which is still moving draws a small amount of fuel into the engine and it ignites because your motor, or plug is a little hotter than it should be. Does this happen all the time, or just when its good and hot? i.e. will it do this after say 2 minutes of run time, or only after a ride? You may be on the edge of detonation if its getting that hot.

[motordude]

Is your air filter clean?

Very clean, Nice and new!

Ah, I feel better now that I am in this "UN-official" BR Fart club!
I will check the valves though, just to be safe.

[motordude]

It MIGHT be that after you shut the ignition off the piston which is still moving draws a small amount of fuel into the engine and it ignites because your motor, or plug is a little hotter than it should be. Does this happen all the time, or just when its good and hot? i.e. will it do this after say 2 minutes of run time, or only after a ride? You may be on the edge of detonation if its getting that hot.

Not everytime, usually after a decent ride.............wont do it after a two minute idle

[El Camexican]

I have been told, thats a tell-tale of valves in need of adjustment... (i cannot prove what I have been told, but my ES does it too)

That makes sense. The valves need to sit in the seats in order too pass their heat into the head and "cool" If your valve lash is too tight the valves spend less time in contact with the seats and will get hot and "burn" as they say. Summers over, time to work on your ES!

[dougspcs]

It seems normal for this engine/muffler style..

Not a indication of any issue..forget about it and ride!!

[muthey]

do you let it idle for a minute before shutting it down? or just straight pull in the yard and shut it off? I know if I just shut my 225dx off right after running it like a great ape it sometimes farts but if I let it idle for a minute it just shuts right down nice and sweet

[El Camexican]

It seems normal for this engine/muffler style..

Not a indication of any issue..forget about it and ride!!

Like I tell my buddies: "If you can't figure out where a noise is coming from, just hold it wide open and you'll know soon enough" :beer

[threewheelin-feelin]

im also a member of the fart club lol....mine does it almost everytime

[Chazz of Blades]

Aye, the old girl has a bit of a pootin' problem.

[bigredridr]

when i ride with a couple of my friends who have 250es 2 85s and 1 87 after we shut them down they all "fart" within 5 seconds of each other. mine has been doing it since i have owned it about 3 years and i ride it alote with no issues, and "farts" after any long ride

[motordude]

Its nice to hear that I am not the only one with a flatulence problem

:lol:

[dougspcs]

No we've all got gas!!

[Xpress]

^Some of us just deny it! :lol:

Might be running rich maybe? My Jeep was doing it for the longest time where it would kick over once or twice after I killed it, and lazy me finally figured out it was running too rich.

[hublake]

I must have one that is not right. I have own my BR since new and it never does that.

[El Camexican]

I must have one that is not right. I have own my BR since new and it never does that.

Better get that looked at!:Bounce

[atc007]

I have a LOT of miles on Big reds,,,don't ever recall this!!!!!!!! I may have to pull one out and go for a ride!! I'm really curious now !!

[Nubbinz]

I think its heat related. My 93 king quad farts after a hard ride, especially a run up the creek or thru my mud pit where theres lots of red lining... my friends mid 2000s quad does it too. Im always pretty gentle towards trikes, never redlined one or rode one full speed for over 10 seconds... and I've never heard a trike fart. I think that's because Ive never done enough high rpm riding on one to heat it up enough for the heat+ unburnt fuel theory. One other theory I havnt seen anyone on here mention is I know on cars they have vacuum hoses connected to the carb that can make a popping noise. I know at least on early 90's honda cars they have a designated vaccuum box on fuel injected models that does nothing but suck air for something or other... radiator maybe? Anyways I wouldnt worry about it and as far as the valve suggestion if it isnt burning oil or spitting oil I think your valves are fine.

[ps2fixer]

I'm in the club as well, 250sx does it. My mudder 250es don't seem to do it hardly ever, if at all, but it does have a cobra exhaust.

[jeffatc250r]

Low grade fuel will cause it in both of my b-r's
93 octane seems to keep mine from doin it

[fabiodriven]

I use 93 octane and mine does it about half of the time.

To all the keyboard jockeys trying to diagnose this "problem", there is no problem. They all do it, it's the nature of the beast.

[kb0nly]

To all the keyboard jockeys trying to diagnose this "problem", there is no problem. They all do it, it's the nature of the beast.

Agreed... I have ridden quite a few 250's that give a "nice ride bud" salute when you shut em off. I would probably take more notice if it did NOT do it... LOL

I have noticed on a couple of them if you came to stop and idled for say 20-30 seconds then shut off it won't always do it, and if it does its less noticeable. But if you just go from riding to stop and off it farts. I believe its unburnt fuel popping off in the exhaust because one 250 i rode for a while never did it, but it had an aftermarket exhaust on it also, free flowing exhaust keeps it from building up and popping off.