Drain the carbies

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Drain the carbies

Postby Freddy » 09 May 2019, 08:22

The importance of draining the carbies anytime the bike is going to be unused for a period of time was driven home to me today.

Been away for the past couple months, with the bike parked up on a battery tender. It always starts first crank, but not this time (yes I know to prime the carbies). Checked fuel coming from the float bowl drain screw, and good spark at the plugs. Just refused to start, other than the occasional 'splutter' when cranking it over (telling me the problem was definitely fuel related).

Anyhow finally got it firing on one cylinder, then two, then after running rough it finally sprung into full life. Clearly the jets had become gummed up from the fuel evaporating out of the bowls. Fortunately seem to have been able to get this to clear and hopefully have avoided a strip and clean job. Had it sat for much longer this gum would have likely set rock hard. A road test tomorrow will confirm it has successfully cleared.

P.S. This has nothing to do with ethanol as its NEVER used. It was simply caused by the full bowls evaporating dry. In future the bowls will definitely drained if I know the bike isn't going to be used for a period.
Freddy
 
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Re: Drain the carbies

Postby Swampy » 10 May 2019, 11:56

Freddy, when I've stuck my bike in its bag in the winter time I've always drained the carbs, last March when I got it out and refilled the tank etc I had fuel leaking from the carbs, someone mentioned that the seals etc all dry out hence the leakage.
So last winter I decided to leave the fuel in them and when I started it in March of this year all was fine....
It seems what works for one bike may not work for another :(
Swamps :)
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Re: Drain the carbies

Postby Freddy » 11 May 2019, 05:35

Swampy wrote:Freddy, when I've stuck my bike in its bag in the winter time I've always drained the carbs, last March when I got it out and refilled the tank etc I had fuel leaking from the carbs, someone mentioned that the seals etc all dry out hence the leakage.
So last winter I decided to leave the fuel in them and when I started it in March of this year all was fine....
It seems what works for one bike may not work for another :(


If the bike was stored when it was too cold to ride in the UK (something like 9 months or so I expect), then I would be surprised if any fuel remained in the float bowls all that time. I would have expected it to have well and truly evaporated away after several weeks. But maybe it doesn't in a UK Winter as it requires a temperature above -43C (-45F) for petrol to start evaporating.

In Sydney there is no way my bike will start without priming the carbies if I didn't ride it for even as little as 3 to 4 weeks. The carby bowls will have evaporated bone dry. I can loose 1/4 tank of juice in that time from evaporation from the tank (and that's with the bike stored in an external garage). There is supposedly some membrane in the fuel cap to stop tank evaporation from the breather pipe, but it seems to be clearly no longer doing its job.
Freddy
 
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Location: Sydney Australia

Re: Drain the carbies

Postby Swampy » 12 May 2019, 17:14

Luckily we don't get temperatures that low in the UK, -5 and sometimes as low -10 but only on the odd day during the winter months.
I also prime the carbs when the bike has been sitting for a week or so, but that's just in case they've evaporated at all.
This year it was fine when I put it back on the road after a 5 month rest, started first time I'm pleased to say :)
Swamps :)
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Re: Drain the carbies

Postby Freddy » 13 May 2019, 05:37

Swampy wrote:Luckily we don't get temperatures that low in the UK, -5 and sometimes as low -10 but only on the odd day during the winter months.
I also prime the carbs when the bike has been sitting for a week or so, but that's just in case they've evaporated at all.
This year it was fine when I put it back on the road after a 5 month rest, started first time I'm pleased to say :)


I was joking about the weather in the UK. However the point being that leaving fuel in the carbies for long term storage to prevent seals drying out doesn't IMO stack up. And that's because the fuel will relatively quickly evaporate away and the seals will be just as dry in no time as if you'd deliberately drained the carbies.

The only difference will be additional sludge in the carby bowls from the fuel evaporating away. That's what causes problems, fuel evaporating and leaving behind gum and sludge that sets like cement in the jets when it dries out.

P.S. The only part of a carburetor that I could see having a problem from 'drying out' would be in carbies with genuine leather accelerator pump plungers.
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Re: Drain the carbies

Postby grasmere59 » 15 May 2019, 21:22

I drained the fuel from mine most winters untill the last,the winter before i drained them and when i refilled them fuel leaked out everywhere untill the seals expanded and stop the leaks.
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Re: Drain the carbies

Postby Freddy » 16 May 2019, 02:24

grasmere59 wrote:I drained the fuel from mine most winters untill the last,the winter before i drained them and when i refilled them fuel leaked out everywhere untill the seals expanded and stop the leaks.


I'm repeating myself I know, but to think that problem can be eliminated by not draining the carbies requires a belief that fuel will remain in the carby bowls for 3, 4, 5 months. And as the only 'seals' are in the fuel line connections, not only does fuel need to remain in the bowls, but the fuel lines as well, meaning completely full with next to zero fuel evaporation over that extended time.

As such no 'priming' of the carbies after this extended time would be necessary and the bike would start straight up with the fuel tap in the 'run' position with just a bit of choke.

I'd be prepared to bet my house that a bike left sitting for 3 or more months will not start unless the carbies are first primed because most if not all the fuel in the bowls (let alone in the fuel lines) has evaporated away. That's the very reason a 'prime' function is incorporated in a vacuum operated fuel tap, because the fuel in the carbies will evaporate away if the bike is unused for an extended period and so won't start.

P.S. The most common reason I've found for 'fuel leaking everywhere' after a bike has been parked up for some time is 'flooding' caused by gum and crap from evaporated fuel stopping the float valve/s from seating correctly. The other major problem is no fuel at all getting into the carby/s because the float valve is gummed up and stuck in the shut position. Both these problems may resolve themselves. I was even able to get my gummed up jets cleared once I was able to get one cylinder firing. Best to avoid these potential problems in the first place.
.
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Re: Drain the carbies

Postby grasmere59 » 16 May 2019, 07:30

The leaks were definately was coming from the connections from between the carbs,if i don't drain the float bowls i get no issues with leaks.
I leave the petcock in run all the time and just start the bike every couple of months and spin it over first with no choke to get the oil pressure up and then it goes first time as soon as choke is applied.
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Re: Drain the carbies

Postby Freddy » 16 May 2019, 13:08

grasmere59 wrote:The leaks were definately was coming from the connections from between the carbs,if i don't drain the float bowls i get no issues with leaks.
I leave the petcock in run all the time and just start the bike every couple of months and spin it over first with no choke to get the oil pressure up and then it goes first time as soon as choke is applied.


Perhaps its related to the use of Ethanol. My bike sat around in a garage unused for many years before I bought it, so the carbies would have been bone dry for all those years, and it hasn't had any problems with fuel leaks. I never put ethanol fuel in the bike (ok once when there was no other option and it ran like crap, so never again), and its reasonable to assume the previous owner probably never used it either.
Freddy
 
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Location: Sydney Australia

Re: Drain the carbies

Postby grasmere59 » 16 May 2019, 17:12

I'd say it's definately the Ethanol content in the fuel in the UK nowadays that is causing the issues.
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