Backfire at Startup!!!!!!

[g21-30]

I haven't been able to ride since Sunday, so I finally hurried out just before sundown tonight. It was 64 degrees F. Turn the ignition on and barely moved the choke. Hit the start button and BANG! Almost jumped off the bike. Let me tell you, normally nothing makes me jump, but my "virtual" behind was already sitting on top of my wife's Jeep Wrangler (parked in front of me).

Yes, my friend, I read everyone of the threads at the kawi forum about this. Just wanted to share my experience with everyone. Almost 700 miles on the bike and made it thru the winter without this occuring. I will be expecting it next time.

[kkim]

[athimmel]

Tell you one thing...if it happens at 7 am, it will wake you up.

It will wake you, your wife, your neighbors, people in China...

[Sailariel]

They seem to do that on ocassion--really don`t know why--but they do. I sort of like to think that Kermit is clearing his throat.

[Viper-Byte]

Mine will occasionally backfire at startup. I am actually trying to replicate it so I can find the cause.

I played with the throttle when it was off lastnight and this morning before starting and no backfire...

[Rynownd]

First time I heard it, my bike was backed up to my house, so the pipe was opening about 3ft from a wall.
...had to change my pants after that one.

[aloh]

it happened to me again today for the first time in months. It gave me a bit of a scare when i started it up in the garage to roll out...

[TheDuck]

I get a nasty afterfire out the exhaust with a nice burst of flames! Its LOUD! It happens at least once a week when starting it from cold first thing in the morning. It scared the crap out of me the first time. Choke or not, there is no consistency to it.

One morning a bunch of gangbangers were across the street hanging out with one of the teenage boys over there when it FIRED! They all ran for cover, you'd of thought that there was a driveby going on, haha.

Just glad I didn't get shot!

[paterick4o8]

Hey! This happened to me too! Gave me a fright at first. I just assumed it was because of my aftermarket slip on not installed properly since it was a DIY for me.

I always cover my hear when I start it up now but it hasn't happened for a while. When it was happening my pipe was about 3ft or less from the wall too, kept in an underground garage at my condo. So idk.. was it the cold in that big garage, the distance from the wall, my slip on, of all of the above? All I know is that it stopped doing it.

[Reddoak]

If mine sits for more than 2 days, I kind of expect it at this point. I only get it maybe 1 time out of 5, but it's pretty damn loud... I've learned to cover one ear (the one closest to the exhaust,) especially on cooler (<70*) days.

[Justanothermp5]

mine did it once, before i wrecked it
but yea i didnt even notice it till my mom was like, wtf was that lol

it was pretty loud though, but i have a full face so i guess that deadens the sound

[paterick4o8]

whaa wth?? it did it today again for me.. but it was sunny and temperature in the mid 60s outside.
last time this happened was almost 2 months ago. I don't get it

[kkim]

that's the point... nobody gets it.

[ride2max]

It happen to me yesterday when i try to start my bike, suddenly a cannon firing sound came out from my pipe after almost a week i didnt use my bike even malaysia weather is hot all day long.

[komohana]

just curious and maybe i missed the answer to this...is it happening only during start-up?

[kkim]

yes

[craha]

I have around 1200 miles on my 09 and it's happened to me twice.

[komohana]

Originally Posted by g21-30

backfire due to the sensitivity of internal transitional passages. This condition cannot be corrected."

i see...

so...yer bike...got hot farts is all

[ride2max]

Regrading with the backfire at startup, i ask few of my friends, they said maybe there some fuel still trap inside the carb. They advise is not to itchy hand try open the throttle when you want to stop the engine.

[noche_caliente]

girls don't fart, remember?

[sm0kediver]

Has my first backfire today. 646 miles on the bike, temperature in the mid 40s... first crank of the day and it went Bang! It wasn't like a gun. More like a small firecracker.

[Nemy]

ooo my backfire devirgining was like a gun. Happened last week (500+kms). Thankfully I didn't freak out cause I remembered this thread

[sm0kediver]

I read that thread. My personal observations:

I don't play with the throttle when it isn't running.

I crank it without the choke.

It backfired anyway.

I prefer the whistling gas tank anomaly to the exploding engine conundrum



That's all for now

[Lurkable]

10k miles and not a single backfire. Sometimes I wish it would happen just once so I know what everyone is talking about when they say it's "loud."

[TheDuck]

Originally Posted by g21-30

Yep, mine does both! I don't mind the whistling and I've grown to expect the BANG or the squirt like yesterday morning!

It squirted? It must really like you!

[Nemy]

Originally Posted by Lurkable

10k miles and not a single backfire. Sometimes I wish it would happen just once so I know what everyone is talking about when they say it's "loud."

jeebus! Don't tell me you've got 10k on an 09 already?!

But if you've owned a pre-gen, it didn't seem to backfire on those - or atleast it never happened to me. After 500kms on the new-gen, though, I thought I got shot...

[TheDuck]

Originally Posted by Nemy

jeebus! Don't tell me you've got 10k on an 09 already?!

But if you've owned a pre-gen, it didn't seem to backfire on those - or atleast it never happened to me. After 500kms on the new-gen, though, I thought I got shot...

I still never had an actual "backfire." Its always an AFTERfire. Where the explosion occurs out the EXHAUST, not out of the carbs.

Of course this was more obvious when I upgraded to the AreaP exhaust. No baffles or flip-flopping chambers in there to contain it.

If I give it a little rev to 5k let it wind down a bit and fiddle with my run switch at a red light I can make it POP really loud scaring the other drivers around me. At night I even get a nice 24" blue flame. If I had a catalytic it would probably be harmful, otherwise it sure is fun!

[Ramen]

The motorcycle is irrevocably damaged. Please send it to me for proper disposal.

[kkim]

http://www.2carpros.com/how_does_it_work/backfire.htm

What is a Backfire?
There are typically two kinds of engine backfires, one is generated from the intake manifold of the engine, and the second is expelled from the exhaust pipe at the rear of the car. A backfire is an explosion of sorts in the intake manifold or the exhaust system. A backfire occurs when there is an imbalance in the air to fuel ratio required for your vehicle to operate properly. If the fuel mixture is too lean (not enough fuel) you may have a backfire in the intake, or too rich (too much fuel) you may get a backfire out of the exhaust system. Most backfires are easily repaired by correcting the imbalance and providing a greater or lesser percentage of fuel to the mixture.

[snowlife]

Originally Posted by kkim

http://www.2carpros.com/how_does_it_work/backfire.htm

What is a Backfire?
There are typically two kinds of engine backfires, one is generated from the intake manifold of the engine, and the second is expelled from the exhaust pipe at the rear of the car. A backfire is an explosion of sorts in the intake manifold or the exhaust system. A backfire occurs when there is an imbalance in the air to fuel ratio required for your vehicle to operate properly. If the fuel mixture is too lean (not enough fuel) you may have a backfire in the intake, or too rich (too much fuel) you may get a backfire out of the exhaust system. Most backfires are easily repaired by correcting the imbalance and providing a greater or lesser percentage of fuel to the mixture.

I agree.
My bike, (bmw f800gs) backfires in a minimal way only, but only while riding This occurs due to a slip on exhaust that has a bad seal, then you role off the throttle thus extra air gets in exhaust and you get a nice little pop pop pop. No probs, quite nice actually (this is common on this model and very much liked by many owners). One possible cause with the 250r, but very unlikely due to your exhaust construction and no movement at the time to loosen seal.

It sounds like your bikes are getting a huge bang. This is not good for the exhaust, even worse if it is in the intake. A big bang in the exhaust can destroy cats and internal parts.
To diagnose i would be looking at 1. how you turn off your bike, maybe in a way that leave excess fuel in the cylinder/carbie. 2. turning off you fuel tap so that no fuel can leak into the carbie/cylinder (assuming there is a tap).

In both cases (assumed exhaust backfire) when the engine ticks over the first few time the mix may be to rich and not ignite or just not ignite due to cold/other reasons. Result extra fuel/air mix ends in the exhaust, result, backfire.

Good luck

[Cochese]

Mine hasn't yet in 200 miles.

We'll see after the mods.

[Sound Wave]

man, i thought i was in the clear. 1300 miles and had my first backfire at start up tonight. startled me a bit. hope it isn't the beginning of a trend.

[capt_bugaloo]

Hmm. My 2008 let loose with a hellacious backfire yesterday when starting up. That is only the second or third time in over 2000 miles. It had only sat cold over night, and I was starting it the usual way - choke, no throttle.

[sm0kediver]

My second backfire this week at around 850 miles.

[Mo1981]

My '08 has about 4,500 miles on it and it has backfired twice in the past week. It's normally around 60-65 degrees in the morning here. It's getting to where I cringe before I hit the button.
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[B2FiNiTY]

I just popped my backfire cherry today at 5XX miles. hahah it really surprised me.

[paterick4o8]

Originally Posted by B2FiNiTY

it really surprised me.

yup. poppin the cherry tends to lead to that effect. it sure got me

[Rocketman]

i have a feeling it might have somthing to do with letting the bike idle for a few seconds before you shut it down...at least thats the way it is with my sled and stuff

[Viper-Byte]

I usually let my bike idle for 10-15 seconds after a ride before shutting it down and the backfire is not a common occurance. So I don't think it is that.

[Rocketman]

Originally Posted by Viper-Byte

I usually let my bike idle for 10-15 seconds after a ride before shutting it down and the backfire is not a common occurance. So I don't think it is that.

Maybe why that's why its not a common occurrence ? left over fuel in the exhaust system maybe ? Backfiring can also occur in carbureted engines that are running lean where the air-fuel mixture doesnt have enough fuel and the timing too advanced.