Effing Carb Icing

[TSM]

I will suss it out.

The main problem i hear is that the air is too cold.

Is this correct?

As I understand it, carb icing is caused by the carbs acting like a refrigerator. Evaporation causes cooling (high school physics), so the fuel evaporating from the jets cools them. Also moving air causes cooling (that's why fans work). Your carbs are sucking a lot of cold air in, so that will cool them more. The combination of these causes moisture in the air to freeze which can block the jets, causing the engine to cut out.

I haven't ridden a curvy SV with carbs, but on other bikes I've found that the best solution is to let the engine warm up before riding it on a cold day. The heat from the engine should warm the carbs enough to prevent icing from happening. However, you may have to run the engine for several minutes before it becomes warm enough. Even a bike that idles OK can ice once you start riding it - probably because more cold air is being sucked though the carb. In this case, the best thing to do, as Mr Itching says, is to stop by the road side and let the engine warm the carbs again.

No this doesn't work. You see carb icing occurs when the throttle has been held open at a constant opening (more or less) for an extended period of time allowing icing to occur within the carb and the degree of fuel/air mixture passing through is then restricted causing a marked drop in performance.

This normally happens when on a motorway/dual carraigeway for 20 mins or so when it's cold and damp.


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You could put some kind of intercooler on, if you cool the air down below 0C there won't be any moisture to freeze

Originally Posted by jonboy

No this doesn't work. You see carb icing occurs when the throttle has been held open at a constant opening (more or less) for an extended period of time allowing icing to occur within the carb and the degree of fuel/air mixture passing through is then restricted causing a marked drop in performance.

This normally happens when on a motorway/dual carraigeway for 20 mins or so when it's cold and damp.
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I haven't experienced this. I've only had carb icing when the engine isn't up to full temperature, never on motorway riding. Having said that, I haven't done a lot of cold weather motorway riding on a carbed bike, I'd always use the (fuel injected) Ducati for that sort of thing.

I love carbs and think FI is only now becoming as good but two things irritate me about carb icing.

First, if a car manufacturer released a car that stopped when the temperature dropped it would be all over Top Gear and Watchdog etc etc. Being a minority (bikers) Suzuki get away from it. I would welcome legal action being taken against manufacturers who are negligent in this way if someone could prove it was because of carb icing.

Secondly, I find it real difficult to predict when carb icing will occur. It isn't as simple as the temperature dropping. This means that Profst and Optimax are only useful if you have predicted correctly.

By the way it makes no difference whether the engine is hot or not, especially on a twin with all that space between cylinders. Perhaps IL fours fare better as the carbs are warmed by the block?
Can any Hornet owners comment?

[rictus01]

Originally Posted by jambo

What a plan, now the trick is to hide the girlfrind's hair dryer so it hooks up with the intake. Gives you a little super charging as well!

Course I'll need an adaptor to get it to run off 5% of it's normal voltage and a lot more current... where did I put that electronics manual...

240/12v inverter, now that's something I've not tried, Hmmmmmmm?

[jambo]

Originally Posted by huge

Perhaps IL fours fare better as the carbs are warmed by the block?
Can any Hornet owners comment?

I've never had a problem on my bandit, which (like the SV) has carb heaters. However, Joe's Thundercat IL4 600cc, does suffer it, and he's got a fairing! Ah well, seems to be a bit mysterious this one!

Originally Posted by jambo

I've never had a problem on my bandit, which (like the SV) has carb heaters. However, Joe's Thundercat IL4 600cc, does suffer it, and he's got a fairing! Ah well, seems to be a bit mysterious this one!

Some carbs are worse than others. The stock Keihin carb on my harley used to ice really badly. I replaced it with an S&S carb which doesn't suffer too badly, though iced a bit this morning.

Originally Posted by jonboy

Sounds simple Joe but weather conditions change rapidly and it's not just down to cold, there's also dampness to consider too. At approx £2 a shot per tank, FST is simply hideously expensive for us financial mortals. Yes Optimax etc ain't cheap but it's still cheaper than (the admittedly superior) FST.


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Red ex or Wynns Dry Fuel do the same job. I usually get myself 2 bottles of Wynns Dry Fuel (£10) every 4 weeks during heavy winter weather. Usually lasts my 1200+ miles.

Premium fuels work well too.