Drain carbs if sat for a week?

Is there a fix? bike runs fine but as said if I don’t run it regularly I have to drain the float bowls....

[Mr Gazza]

The answer is 42.

[Nickj]

saturday for a week would be good unless it's one I'm working

You'd be fine to leave them for weeks, months probably not

[Darkness]

What are you afraid of if you leave them full?
They are as likely to stick open (And overflow when filled) as shut.
That said, I only fill mine with Esso Super, so there's no risk of ethanol and less risk of water.

I was hoping for a fix that meant I didn’t need to drain them to start it up when I go for a ride after not using if for a while. I accept that they may need draining at the beginning of the season for example, but not every week?
I don’t remember ever having to do it on my carbed 750ss I had a while ago....

[Mr Gazza]

I still don't really understand the question, but I am intrigued.

If you don't use it regularly why are you draining the carbs every week and what does this achieve?

[Flip]

First of all are you running the standard CV carbs or a pair of FCR’s?

Like Mr G I am also a little perplexed as to why you feel you need to drain them for easy starting after just one week.

Give us some details and I’m sure we can help.

[Ron1000]

I’m also perplexed…easily done tho so thought it was just me.

Can’t you just fire the bike up, run it a wee bit?

And put some fst-pro fuel stabiliser in it.

Should have made it clearer, bike won’t start if not used for say a week. When I drain the two carbs it fires instantly

[Nasher]

They all do that I'm afraid, but it's mainly thought to be fuel evaporating out of the float bowls and the Vacuum fuel pump not being able to fill the bowls quick enough.

There are ways to minimise the effect, such as ensuring the battery is in good nick and the complete set of battery and earth cables supplying power to the starter are in good condition.
Plus making sure the fuel pump is up to scratch with a rebuild kit.
Also of course that the coils, spark Plugs etc are good.

I start my M900 fortnightly if it's not going to get used, and it starts almost instantly.
You can of course convert to an electric fuel pump, or I looked at fitting an outboard engine primer bulb and gave up.

You are not far from me if you need any help.

Nasher

Thanks, the PO suggested regular start ups so I’ll do that but not over winter when it’s likely it’ll be laid up. New battery, etc already and as I said, when it’s in regular use it’s an instant starter anyway . Thanks for the advice everyone

[utopia]

I'm still confused.
If fuel evapouration from the float bowls is preventing easy starting (as happens to all carbed monsters), why would draining the float bowls be an effective cure ?
Surely that would simply worsen the problem ???

In fact I believe that Dookbob used to do exactly the reverse, ie he used a syringe to inject fuel into the float bowls via the drain tube to refill them fully.
He later fitted a manual priming pump to do the same job ... (there's a thread in the archive somewhere).
Me, I don't bother. I merely keep pressing the starter until it fires.
If its been standing unused for a week or so, it usually splutters for a short while until the float bowls top themselves up.
Its done that since I first bought it, when it was virtually brand new.
However, when its used regularly it starts very readily, almost seeming to anticipate my thumb as it approaches the starter button, and runs cleanly straight away.

[Nasher]

'U' Hi.

I'm assuming the carbs are being gravity fed somehow through the vacuum tap during the process and draining the bowls is actually purging the air and allowing fuel to part fill them.
It would appear to be the most viable option.
I'd agree that actually completely emptying the bowls would make things worse.

Nasher

[utopia]

Yes, I see your point, Nasher.
But are the float bowls not vented anyway (I'm not sure tbh), in which case there would be no air lock possible.
If they're not vented then how would fuel flow into them anyway ?
The only rationale I can come up with is that the float valves are sticking slightly, thus preventing fuel flow until the bowls have drained significantly, ie enough to crack open the float valves due to the added weight of the (no longer floating) valves ....?
I'm not convinced of this analysis tbh, but its all I can come up with.
..... other than "there is no problem", that is.

As suggested earlier, using low or zero ethanol fuel from Esso or BP would minimise any gumming up of the valve or deterioration of the rubber seat .... always a good ploy in my opinion, whether there's an existing problem or not.

[Nasher]

Good point, perhaps the vent tubes have been joined together, kinked or similar.

Strangely I had a neighbour round only a few weeks ago who'd put a new/refurbished pair of carbs on his 1936 Riley Kestrel. I normally do a lot of that sort of thing for him, but the specialist who'd supplied them assured him they just needed bolting on and possibly the mixture adjusting slightly. He'd planned on getting me to adjust them and the timing once he'd got it started.
The 1.5l 4cyl just would not start, so I went and had a look and found completely dry float bowls despite the fuel pump obviously pumping fuel.

I found the 'Brand New' float valves full of a sticky jelly type substance. It started fine after we'd cleaned them out.

Nasher.