Bad fuel or timing prob?

I need some help and advice from the members here...

I was out on a ride and everything was fine on the bike, i stopped for some fuel and i started realising I was losing some power, not an awful lot, but there was some. I thought it would normalise after the carbs got more fuel running through them, but its still going on after i reached home. Whats happening is theres a short of 'popping' noise, especially when i hit 5k+ rpms. I've had this happen to me before and it was a timing problem, and I kinda suspect thats what is happening, but since I've never had bad fuel before I was wondering what happens when you get bad fuel? And since I'm a noob at this, what are the sort of problems you get with bad fuel and timing? what signs are indicative that its a timing problem?

I've checked a few things so far, its rather late and I haven't had a good look at it, but I've checked the fuel line and fuel is flowing out steadily and so that rules out blockage I suppose, theres spark on all 4 plugs, and they all look good, thats all I've had a chance to fiddle with so far, Just need some input and advice for me. Please bear with me as I'm not really that mechanically minded. Thanks

I have had bad fuel several times.Drain your
float bowls into a small cup (no styrofoam),
and look for contaminates.Water will be small
globules at the bottom.Small specks of rust
will look black.If you find some of either,
you will have to turn the petckock to on and
keep draining untill it clears up.The symtoms
are usualy very similar to what you described.

dont forget there is a filter in the petcock valve and inside the float valves on some models as well.if u are geting dirt i think u could have a starving symptom, like u are running out of fuel, if it blocked the pilots.

Thats whats fantastic about this forum, barely 20 mins after my initial post and already someone answers :woohoo:

After reading it I just had to drain my carbs immediately, sure enough there were some black specks in the fuel, had to drain it a couple of times, here I am running back and forth from my bike with a cup full of gas... think I may have inhaled too much :pinch:

As soon as the gas cleared up, I just had to ride it and see ( who cares if its 12.30am?) , And it might be the placebo effect, but after a short 10 min ride, it did seem ok, still not back to normal, but much better, think I'll continue to drain and check the filters to see if theres anything else to clear, guess it wouldn't hurt to just check the timing tomorrow anyways :dry:

just one more question, if the timing checks out and if it is bad fuel, would it be wiser to empty out the tank? Just wondering what would happen if I continued on the bad fuel, its not that its horrible, as long as I don't push the bike too hard it seems to run ok, Guess I shouldn't really try to use other brands of fuel, just didn't have a choice then... :S

Empty the tank and with a flashlight get a
good look inside.Sometimes gas additives will
break loose existing rust deposits in the gas
tank.If rusty,drop in some lead buckshot,a
couple of cupfulls of gas,and swish it around
in the tank,empty and flush with gas.Repeat
untill tank is clean.If you have a screen on
your petcock inlet tubes you may want to remove
it first.