Back firing...surging....running rough

[scottyintex]

The engine is surging...back firing...running rough. This started after a long run in the country. I was running it out of gas so I could replace the petcock. Drained the gas out..replaced the petcock. Thinking it might be the gas...I put just enough in to get me to a good gas station...rode it a bit but didn’t improve. Any ideas on where to start. Oh, this is on a 74 R90/6

[Bob_Roller]

Drop the carb float bowls, see if anything is in there, that shouldn't be, water,debris .... .

[montmil]

Ditto, Bob's comment. You may have drawn down the fuel level far enough to pick up some condensation.

[donbmw]

I had my spark plug wires going bad on my 82 R65 and it acted more like a fuel problem to me. I had check for something in the tank, float bowls and even went through the carbs. Everything ran fine for a little and then started cutting in and out just like it was running out of gas. Put new wires and caps no problems since.

Don

[scottyintex]

Up date...I did as advised dropped the carburetor bowls.... spit shined them..replaced the spark plugs...didn’t replace the spark plug wires as they are new. Everything seems to be back to normal...engine running smoothly..no surging or back firing. But there is a tiny bit of doubt lingering in my mind as to what the problem was... think it was water in the gas but........ Going for a long run this afternoon is 82 degrees..perfect riding weather...but taking the phone just in case. Last year I bought a aluminum trailer..light enough that my lovely bride can hook it on to the pickup if I get stranded in the middle of now where........again. Your right Monte she is a Saint...I chose wisely. Thanks guys.

[tvrla]

Sounds like the classic 'water in the fuel' syndrome.

To remove all doubt, drain the tank completely, then add new gas.

Just to make sure - you do know the water is heavier than gasoline and stays at the bottom? It'll look like a coherent bubble rolling around down there.

[Bob_Roller]

Not a bad idea every couple of years, to drain the fuel out of the tank remove the fuel tap(s) and let the tank sit in the sun for a while .

I've used the warm exhaust air from a shop vac to dry out the interior of a fuel tank .

I used to drop the carb float bowls every year to clean them out .

Always had an accumulation of fine grit and a couple of globs of water in the bowls .

About 8 years ago, I added an in-line fuel filter, no sediment or water in the float bowls since .

This is the filter I've been using for the last 6 years .

http://www.itw-fastex-cva.com/images/stories/data-shts/visufilter/8437-00-9909.PDF