Backfire, Flames and 2 cylinders

OK my bike is getting there (slowly)
i got the pods on and rejetted the carbs.

I got it started up and idling ok, took it for a quick spin around the block and ....... Ran out of gas (yeah i know, what a dickhead !!!)

anyway i got some more fuel in it and got it started and noticed 1 & 2 cylinders are not firing. This is probably why i'm getting big backfires ?? we're talking flames here !!!
I'm just going out to check the plugs ( i'll let ya know what they are doing)

does anyone have any suggestions to what i should be looking at ?

p.s Where or what do i need to do with the rubber hose that fitted into the top of the old airbox (it's about 1 inch black hose, is it part of the smog system ?

thanks

OK as i thought
getting a nice blue spark on each plug BUT....
1 & 2 plugs wet and black. 3 & 4 black to dark tan color but dry

sounds like a carb problem. as far as that hose goes get a k&n breather filter for it. it is your crankcase breather.

Off the top, 1&2 wires crossed? coil wires are 1-4, 2-3. Hoses from top of airbox usually go to AIR sol's. a total of 3. if valve cover have spigots/reed valves/ examine.G

Just noticed something strange (maybe)
just check the fuel lines etc. and as i was pressing the starter switch i noticed fuel being sucked down the hose from the petcock that goes into the top of carb no.2
Is this right, should gas be traveling down that hose (the smaller one)I thought it was a vacuum hose ???????

Are the backfire flames from the exhausts or from the carbs?

If not already done, would assure valve clearances being to specs. Because too tight intake valve gap can cause backfire through the carb.

Fuel line from petcock does not go into top of carb.

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Good Luck!

Here's a CV carb assembly with center tee fuel pipe 92005.

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timebomb33 wrote:

sounds like a carb problem. as far as that hose goes get a k&n breather filter for it. it is your crankcase breather.

Thinking the crankcase vent hose is usually fitted into bottom of air box, whereas triggerbilly described a hose as going into top of airbox.

triggerbilly wrote:

Just noticed something strange (maybe)
just check the fuel lines etc. and as i was pressing the starter switch i noticed fuel being sucked down the hose from the petcock that goes into the top of carb no.2
Is this right, should gas be traveling down that hose (the smaller one)I thought it was a vacuum hose ???????

Is it possible that the vacuum line from carb to petcock has been accidently attached to the petcock fuel outlet (instead of the petcock vacuum nipple) and thereby allowing fuel to be sucked into the carb vacuum nipple (petcock set in PRI position)?

triggerbilly wrote:

Ran out of gas...got it started and noticed 1 & 2 cylinders are not firing....

Running dry may suck a lot of grit and crud from the tank. If an inline fuel filter isn't fitted, the grit and crud may obstruct the float needle/seat interface, resulting in overly high fuel level in float bowl, causing over-rich mixture, which can flood the cylinder and foul the spark plug.

Good Luck!

thanks for all that patton.
The thicker of the two tubes running from the back side of my petcock is going to the tee on my carbs (inline filter). And the thinner one on the left as you look at the petcock is going to the top nipple of my number 2 carb.
it seems to be dripping slow and constant on the 'on' 'res' and prime position
(my carbs have been leaking ever since i bought the bike, so I'm guessing this has something to do with it)

the thick tube that was running to my airbox is the hose from my vacuum switch (so it's just hang there at the moment)

maybe a daft question but Is there a way to rip all the vac lines out and block off the nips ?

thanks

I don't think running low on gas has knocked out 1 & 2
I've had trouble with them since i bought the bike too.
I've had it running on all four, but they ain't firing at the moment