Backfiring through the #1 carb?

[Detman101]

Does this indicate a rich condition or a lean condition?

I'm guessing lean or overly cold. The bike just started doing this while riding in the snow yesterday.

Could be time for some fuel additive...

Thank you,
Dm of mD

[Detman101]

WAIT!! Could it be a timing issue?

I thought about it a little and perhaps the #1 cylinder is firing when the intake valve is open or something?


Dm of mD
1981 GS750L TSCC

[focus frenzy]

WAIT!! Could it be a timing issue?

I thought about it a little and perhaps the #1 cylinder is firing when the intake valve is open or something?


Dm of mD
1981 GS750L TSCC

could be!

[jtcrespo]

I'm interested in the answer to this as well. Getting backfire through #2 until bike gets warmed up. Hoping it's a carb synch issue and doing a synch soon to see if that gets rid of it.

[KEITH KRAUSE]

Is the back fire more like "spitting" out the filter(s)? This is almost always a lean mixture condition.
It can be a lot of things. Dirty carb passages in the pilot circuit...a sticking float needle valve...float level not adjusted right...vacuum level too low on a carb...mixture screw/pilot screw not adjusted right...pilot jet too small...
The colder weather really exposes lean mixture problems that are not as noticable during other times. If all the above is good, remember that mixture screws (CV's) and pilot fuel and air screws (VM's), are provided to make minor jetting changes to help during cold or hot weather.
When it's colder out, try turning your mixture screws out a 1/2 turn or so. When it's hot or in higher elevations, the opposite can help.
On VM carbs, try adjusting the side air screw out a 1/4 to 1/2 turn to lean the mixture when it's hot out or in higher elevations.

[first timer]

my bike was doing the same thing, back fireing thru the the carbs i raised the needle a 1/2 notch and the problem was gone.

-ryan

[KEITH KRAUSE]

my bike was doing the same thing, back fireing thru the the carbs i raised the needle a 1/2 notch and the problem was gone.

-ryan

It could be that too. In Detman's case, I'm assuming the bike only showed this problem in very cold conditions. I'm also assuming his bike is running fine at all other times. If he raised the needle 1/2 a position, it could cause richness problems at all other riding conditions. But it could still be his needle is lean to begin with and the colder temp's bring on the problem.
Regarding your fix, have you taken any plug reads at 1/3 throttle? I only ask because in my experiences, most of the time when a bike spits, it's more than a 1/2 position too lean. Raising the needle a 1/2 position may eliminate the spitting, but the needle is still lean. But with jetting, we all know there are exceptions.

[first timer]

no i haven't taken a reading at 1/3 throttel i should... i have just been going by plug color when i turn it off, and that is a good color, i also usally run the bike on the main, 7000+, that and the way the pods on my 550 work in my experice if they get kinda dirty then it seems to effect the richness of the bike so i try to keep them clean and at there highest flow, i know this mean the whole bike maybe jet a little rich but it's been working good for me, and i am scared that if i start changing things then i have to go back a adjust every thing. maybe i will, i need to resnyc this spring so why not try droping my mains down from the dj155 to a dj150 both came in the kit and natually i went big.

-ryan

[KEITH KRAUSE]

Well if your set up is working for you and the plugs look good, don't let me get you into trouble! Just ride and enjoy it!

[first timer]

well see how spring goes and how my 1000 is coming, if i get the 1000 up and running then i can break the 550.

Keith, you know any thing about batteries, if so can you check my battery help post.


-ryan

[KEITH KRAUSE]

Keith, you know any thing about batteries, if so can you check my battery help post.

Checked it out and added my opinion.

[Detman101]

Is the back fire more like "spitting" out the filter(s)? This is almost always a lean mixture condition.
It can be a lot of things. Dirty carb passages in the pilot circuit...a sticking float needle valve...float level not adjusted right...vacuum level too low on a carb...mixture screw/pilot screw not adjusted right...pilot jet too small...
The colder weather really exposes lean mixture problems that are not as noticable during other times. If all the above is good, remember that mixture screws (CV's) and pilot fuel and air screws (VM's), are provided to make minor jetting changes to help during cold or hot weather.
When it's colder out, try turning your mixture screws out a 1/2 turn or so. When it's hot or in higher elevations, the opposite can help.
On VM carbs, try adjusting the side air screw out a 1/4 to 1/2 turn to lean the mixture when it's hot out or in higher elevations.

Keith, once again...YOU DA MAN!!!
The #1 carb was lean...way lean...on the mixture/pilot screw setting. The exhaust tone is also a lot smoother now rather than the ragged popping tone I was getting before. And you were right that it was only happening during very very cold weather.

Glad this one was an easy fix.


God bless,
Dm of mD

[KEITH KRAUSE]