Suzuki GN250 Dies when Stopping

[claynz]

Bike starts up fine using the switch before going out riding, no choke needed, but the bike starts sputtering a coupld of times when accelerating on first use but comes right down the road.
I have noticed and it has been getting requent now is when I come to a stop the engine dies, starting the bike doesn't work and need to pull off to the side of the road, usually starting it with some extra throttle seems to work.
It doesn't happen everytime but enough to annoy me.
I think for memory running in 3rd or 4th gears then stopping with the clutch in, fuel tank is full!!
Something is not right?

[jaffa90]

Sounds like a carb strip with the jets out & clean, also checking the needle valve for maintaining the correct fuel height.
Also fit an inline fuel filter to prevent crap from the fuel tap and tank entering the carb.
Q, do you use the fuel tap?

[claynz]

Is the fuel tap the switch that switches between on, off and reserve? then no, I just keep it on all the time

[jaffa90]

[claynz]

Other than that I don't use a fuel tap

[Robby]

Is this a problem that started happening on a bike in regular use (a daily commuter), or has the bike always done this under your ownership, or spent a long time off the road and recently gone back on the road?

If it was standing, I would be expecting to have water in the fuel and crap in the carb. Drain a litre off using the reserve tap to look for water in the fuel, and clean the carb.

If it was in regular use I would expect the fuel system to be good condition. First places I would look for diagnosis are an air leak between the carb and head, or tight valve clearance.

[WD Forte]

It were all fields around here when I were a lad

Apart from that we'd often whip a/the plug out to get a quick idea of
the running mixture.
You know, a quick easy check see if its running too rich or lean before stripping things down.

Don't they do that now?
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bikers smell of wee

[claynz]

The previous owners had the bike for many years with low km's and was garaged, I have had it for only a year, maybe ride it once a fortnight for an hour or two and is parked outside, uncovered
I thought if there was crap in the carb or water in the fuel it would die or splutter while riding it other than dying while coming to a compete stop.

[jaffa90]

""""""" is when I come to a stop the engine dies,""""

""""""" other than dying while coming to a compete stop.""""

Do you mean dying WHEN coming to a complete stop????

[Nobby the Bastard]

What are the carb rubbers like? Excess air getting into perished rubbers whilst pulling to a stop is known to cause the issue you have.
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Sprint ST 1050

[claynz]

Yes complete stop

[jeffyjeff]

This makes no sense, as there is nothing about a carburetor that senses speed, only air flow. As I recall from fuel systems class (probably from about the time WD was a lad) a carburetor uses 7 circuits to fuel the engine over a range of operating conditions. Motorcycle carburetors do not use accelerator pumps, nor do they employ multiple barrels to enhance fueling at high flow rates. Therefore, 5 circuits are employed in a motorcycle carburetor: float circuit, choke, idle, off-idle (transition), and main metering (main jet). Often times issues manifest during the transition between circuits, and it seems that your idle circuit is failing to transition under certain conditions. Could be that it is underperforming every time you close the throttle, but you only notice it at a complete stop because that is when you disengage the clutch..?

The idle circuit operates under minimal airflow, and so small abnormalities will be amplified. Check float level; high float level = rich mixture, low float level = lean.

I would start simple: make sure you have no restriction in the fuel supply to your carburetor, and ensure your idle air screws are adjusted properly according to your manual. Your symptoms suggest abnormal idle circuit operation, and the air screws fine-tune the air fuel mixture at idle. If that does not help, get a rebuild kit for each carburetor on your bike. The kit will contain new gaskets, a fresh needle valve, a guide for setting float level, and new jets. Clean the insides completely, and reassemble with new parts.

Finally, you should get in the habit of shutting off the fuel when you park the bike. When the fuel tap is left "on", a leak in the needle valve or a failed float can overfill the float bowl, the excess fuel will drain into the intake manifold. This can result in hydrostatic lock or fuel dilution of your engine oil.
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History shows again and again how nature points out the folly of men - BOC

[claynz]

Thanks, a mechanic said I shouldn't be stopping in 3rd gear, I should be changing down gears due to higher revs.
I'll make a habbit of turning the fuel valve off when not in use..

[WD Forte]

You can stop in any gear.
fact.
Pull the clutch whilst applying brakes and save kittens lives
simple.

Perhaps your mechanic was referring to engine braking or using the appropriate gear for the speed and conditions?

your malady sounds like the mixture is out, check the feckin plug!
tip:
Do the simple obvious things first.

Otherwise, for example
you may follow the guy who bought a new starter motor
when all he needed to do was clean and tighten the battery terminals
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bikers smell of wee