Carb freezing at full throttle

[truslack]

In very cold conditions, my carburettor seems to freeze in the full thottle position - this can get quite unnerving when you let the throttle off for a corner and you carry on as fast as the bike can go.

I have had this problem a couple of times, once when warming the bike up, and again last night meaning I had to stop at a house by the side of the road and ask for a kettle of hot water.

Any idea what could be causing this? I'm going to take the carb apart and clean it on monday, would it be ok to clean it with meth's or does it have to be special carb cleaner?

Cheers
Mark
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Current: Suzuki RG 125 Gamma, Honda H100, Triumph Tiger 800XC, Suzuki SV650 (minitwin)

[Whosthedaddy]

Lube the throttle cable and linkages.

Make sure that they are not fouling causing it to jam.

Have a look at the butterfly valves in the carb to make sure that they are free and not hindered.
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Current : MSX 125 Past : CBR 900RR Monkeybike : c50 LAC : ZXR750 H2 : FZR600 : ZX7R P3 : YW100 : TRX850: Trophy 900 T309 : GSXR 600 L0: Monkeybike : XJ6S Whosthedaddy

[truslack]

Its not the throttle cable, I looked at the point where it connects to the engine and it is definately still moving when it freezes.

Ta
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Current: Suzuki RG 125 Gamma, Honda H100, Triumph Tiger 800XC, Suzuki SV650 (minitwin)

[ms51ves3]

Add a bit of redex to your fuel can help stop carb freezing.

[Kickstart]

Hi

Suppose it is possible it is ice, but would expect running problems before it stopped the slide moving (ie, ice to stick the slide would almost certainly block the jet before it got bad enough to stop the slide returning).

I would have said the throttle cable itself as a first item. They can be worth replacing fairly early on.

Worth taking the slide out and cleaning it up. Doesn't take much grit (one tiny piece) to cause the slide to stick.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[truslack]

[Finglonga]

[Phil_P]

Sometimes the airflow at high rpm can push the slide just enough out of line in the carb to overcome the return spring pressure. Del Orto flat slides are notorious for this.

Do you find that shutting off the kill switch or ignition allows the slide to drop again? If so, polishing your slide and ensuring there are no high or rough spots to impede travel may solve the issue. If it still sticks, then either fitting a slightly stronger spring in the carb (or even stretching the existing spring slightly) may solve the problem.

I suppose a spot of redex or even two stroke in the petrol might lube the slide enough to help too.
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It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[truslack]

[ms51ves3]

[Finglonga]

[baldy]

i had this once, when i opened the throttle the needle would sometimes come out of the jet, causing it to jam, it was caused by a slightly bent needle. I couldnt even see that it was bent, but after i changed it, it never happend again.
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One day i will rule the world, just not today.

[truslack]

[baldy]

You need to find out if the needle is bent first. I'd give it a good clean up before spending any money.
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One day i will rule the world, just not today.

[Kickstart]

[truslack]

[1016]

Do you have std airbox and filter fitted? - If you are experiencing icing in mouth of carb this is more likely to happen with a stubby aftermarket air filter - might also explain the (what appears to be) weak mixture.

[Kickstart]

Hi

Cold weather = cold air = more dense air = leaner mixture. Most things used to run rich enough for this to not matter that much, but now it is more common for things to be set up fairly lean for emissions reasons. Which can cause an issue when the temp drops.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[truslack]

[1016]

Don't really know your bike well enough to comment Mark, but the main thing is that you have retained the std airbox so won't make things worse as regards icing. I can remember that some K&N filters fitted to cars did require a jet change to a larger size. Hope you manage to cure your problem.

[1016]

Just occurred to me Mark - what is your Bike? (can't see it listed in thread! is it just me?) - I am assuming you have looked up std specifications as a guideline to what jets/needle/settings you should be running?

[truslack]

[stinkwheel]

With regard to the needle. If you take it out, note the position of the circlip before removing it then roll the needle on a mirror. It will be immediately apparent if it is bent.

My guess would be that either the throttle valve is worn/deformed or the venturi body is slightly warped due to rough handling at some point in the past. Not a lot mind so it doesn't effect things unless it is very cold when the differing rates of contraction make it a bad fit.

Throttle cable is still the most likely candidate though.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[davidlewtas16]

give it a shot of wd40 down in to the inlet and it should stop freezing if not the needle may be bent it may need changing but on my car when i had it the throttle was jamming open and i sprayed wd40 in it n it fixed its self be carefull tho

[truslack]

Just taken the carb apart, and it seems like the needle has been slightly damaged, it looks like this:

Is that bad? Its only a tiny deformity but could it be the problem? The circlip flew straight off, does it matter which notch it goes in?

Thanks

Mark
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Current: Suzuki RG 125 Gamma, Honda H100, Triumph Tiger 800XC, Suzuki SV650 (minitwin)