Whats wrong with running a carb dry?

[FLrider]

I've got a few carburated bikes, including an old airhead. I don't ride them all that frequently but when I do, I just turn off the petcock and let the bike run out of fuel.

 

I read in a motorcycle magazine that doing that is bad for the carb. The recommended instead, that I just drain the carb.

 

How is not leaving fuel in the carb, bad for the carb?

 

By the way, If I know the bike will be sitting for a while, I'll fill it with non ethanol fuel. Otherwise, it's blended fuel.

[Tony_K]

If I am reading you correctly it's same end result, just different ways of getting there. Empty the float bowl.

 

Personally, removing the drain is stupid and many people end up with a thrashed hex head or cross thread the thing. Not to mention typically covering the bike and ground with raw fuel.

 

Keep running till it putters out and throw away the stupid magazines.

 

 

[dirtrider]

Evening FLrider

 

Personally I can't see it making that much difference, but draining the carb with the drain plug probably gets just a bit more fuel out than running the engine until it goes too lean to continue.

 

I usually add a bit of 2 cycle oil & some StaBil to the gas tank before storage then ride the bike a bit. That coats the inside of the tank & inside of carb with a bit of oil.

 

[tallman]

Anyone with too many bikes to ride should be banned.

[FLrider]

Anyone with too many bikes to ride should be banned.

 

Just remember that next time you're in my neck of the woods and need a bike to ride around on.....

[Bullett]

FWIW, my mechanic told me to turn of the petcock on my /2 a short way from my destination so that the fuel in the carb burns instead of leaking out. I always forget.

[tallman]

You need some new memory foam, ask Whip for some.

[Bullett]

You need some new memory foam, ask Whip for some.

 

[rich t]

I had a 78 airhead in Michigan, where November to March the bike did not see road. I never drained the float bowls. Instead, filled the tank with fresh fuel, added stabil, and ran the bike enough to get that fuel in the carbs. I then ran the bike once or twice for a couple of minutes (enough time to get the oil to warm up). You've got to keep the battery up anyway. Never had trouble starting the bike.

On the flip side, dry carbs will have likely have a fuel film. If your carbs have cork gaskets, the dryness could also damage those gaskets.

[Rinkydink]

I use Star-tron and non ethanol fuel in my airhead. I never run all of the gas out, but I live in an area where I can somewhat ride year round. I ride at least enough to get the carbs full of star-tron with a tender and no problems so far. YMMV

[BMWRich58]

I had a 78 airhead in Michigan, where November to March the bike did not see road. I never drained the float bowls. Instead, filled the tank with fresh fuel, added stabil, and ran the bike enough to get that fuel in the carbs. I then ran the bike once or twice for a couple of minutes (enough time to get the oil to warm up). You've got to keep the battery up anyway. Never had trouble starting the bike.

On the flip side, dry carbs will have likely have a fuel film. If your carbs have cork gaskets, the dryness could also damage those gaskets.

 

I agree with the second half..."the dryness could also damage those internal gaskets/rubber o-rings."..but the thing about a *film left* well I kinda find that hard to believe,since gasoline evaporates quickly. If not exposed to air,most likely will turn to what many call a "varnish type substance"...as the additives breakdown,evaporate and or precipatate to carb passages or to the bottom of a float bowl.

 

For example, the rubber tip on the needle of a "needle n seat assembly" could possibly dryout/get hard, which then won't allow a good seal and cause fuel to over flow in the float bowl and runout the vent hole. Also high floatbowl levels contribute to a "Rich" running condition for carbed vehicles. Especially common on older "carbed" gasoline fired engines.... Again rubber "o-rings" inside the carb for jets/needles and such can and do get brittle. But with the recent technology in producing gas/fuel resistance plastics/rubbers/o-rings etc in the past 10 or so years,have been preventing those problems of the past.

 

I'm a big believer and practise the "complete drain carb/tank/fuel assembly" when storing a gasoline fired device if stored more than 6 months. I'm thinking lawnmowers/sno-blowers/AirHead motorcycles.....

Come Springtime,add fresh gas,hit the starter,pull the recoil or what ever starting procedure is needed and "BAM" let's get on with it. "NO Leaks,clogs,sputters,abnormal idles"... Been doing this for over 30+ years with all my 4 stroke "stored items" and never ever had a problem come time when it's needed to be put into service.

[rich t]

I had a 78 airhead in Michigan, where November to March the bike did not see road. I never drained the float bowls. Instead, filled the tank with fresh fuel, added stabil, and ran the bike enough to get that fuel in the carbs. I then ran the bike once or twice for a couple of minutes (enough time to get the oil to warm up). You've got to keep the battery up anyway. Never had trouble starting the bike.

On the flip side, dry carbs will have likely have a fuel film. If your carbs have cork gaskets, the dryness could also damage those gaskets.

 

I agree with the second half..."the dryness could also damage those internal gaskets/rubber o-rings."..but the thing about a *film left* well I kinda find that hard to believe,since gasoline evaporates quickly. If not exposed to air,most likely will turn to what many call a "varnish type substance"...as the additives breakdown,evaporate and or precipatate to carb passages or to the bottom of a float bowl.

 

For example, the rubber tip on the needle of a "needle n seat assembly" could possibly dryout/get hard, which then won't allow a good seal and cause fuel to over flow in the float bowl and runout the vent hole. Also high floatbowl levels contribute to a "Rich" running condition for carbed vehicles. Especially common on older "carbed" gasoline fired engines.... Again rubber "o-rings" inside the carb for jets/needles and such can and do get brittle. But with the recent technology in producing gas/fuel resistance plastics/rubbers/o-rings etc in the past 10 or so years,have been preventing those problems of the past.

 

I'm a big believer and practise the "complete drain carb/tank/fuel assembly" when storing a gasoline fired device if stored more than 6 months. I'm thinking lawnmowers/sno-blowers/AirHead motorcycles.....

Come Springtime,add fresh gas,hit the starter,pull the recoil or what ever starting procedure is needed and "BAM" let's get on with it. "NO Leaks,clogs,sputters,abnormal idles"... Been doing this for over 30+ years with all my 4 stroke "stored items" and never ever had a problem come time when it's needed to be put into service.

 

If you're talking 6 months, i'm with you on the complete and clean drain. Hopefully, the bike we are talking about has a lined fuel tank. One of the reasons I like keeping a full tank, is to prevent corrosion in the tank. If you're going that long though, the gas is going to be bad come springtime, so a complete drain may be a better bet.

 

So go for a quick carb cleaning in the spring if that were the case? Always seems like the needles get that fuel film on them.

[elkroeger]

The only thing I can think of is the case where people might, without thinking, pull up to their destination, and then shut off the gas petcock. This would leave the bike idling until the carbs run out, which would risk overheating.

 

Draining the bowl manually is messy and a drag. When I had my airhead, I had to dump the water out of my carbs all the time because I parked out in the rain. I got tired of that pretty quick. Pulling the bowls off is also hard on the gaskets.