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| Lone-Wolf |
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Lone-Wolf
World Chat Champion
Joined: 13 Jul 2004
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 Posted: 20:31 - 28 Dec 2005  Post subject: |
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Wotcha.
Never had a problem with the carb on either of the bikes.
The VW trike however is a different matter. The carb is mounted on a massive long manifold, and also has accelerator pumps fitted. Ride it on a cold, foggy day and you literally get a snowball on the outside of the carb. The way I got around it was to 'box' the engine in - then make a warm air intake to the air filter. There is an aftermarket 12 volt "electric blanket" that wraps around the carb and the manifold. These electric carb heaters could be modified to fit on a bike 
The Ford trike has a water jacket around the inlet manifold - ain't noticed the carb ice up yet.
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L.W. - www.moonshiners.org.uk |
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| Zimbo |
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Zimbo
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| Kickstart |
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Kickstart
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| jonnay |
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jonnay
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| Kickstart |
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Kickstart
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| Posted: 21:13 - 28 Dec 2005 Post subject: |
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| Bezzer |
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Bezzer
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| Posted: 21:19 - 28 Dec 2005 Post subject: |
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| sickpup wrote: |
Carb icing is caused by either the freezing of petrol or water droplets in the main jet or emulsion tube of the carb or carbs. As I understand it normally petrol in the main jet as this is a the smallest part of the carb.
1. As a piston goes down (assume intake stroke for 4 stroke) it creates a vacuum, now as we know from physics at school vacuums are cold.
2. The inrush of air to fill the above vacuum also causes a vacuum over the emulsion tube and a temperature drop.
3. This vacuum pulls fuel through the main jet and up the emulsion tube atomising it as it pulls it up. For the fuel to atomise it takes heat from the carb, the nearest part being the emulsion tube.
Now all this taking of heat caused either by vacuum or atomisation causes the fuel or water to freeze in the jet/emulsion tube.
Happens more on cold days as the inital temperature is lower.
Now if you want a practical demonstration of the above you can recreate it using a 40kg propane bottle and heater with a 8foot long hose outside on a cold day.
Set up the bottle and heater as far from each other as possible with the hose hanging taut between them. Aim the heater away from the bottle and turn it on full blast. After about 45mins to an hour you will see ice crystals forming around the bottom of the bottle and if you leave this running the ice crystals will reach about half way up the bottle before it runs out. The reason this happens is that as gas leaves the bottle to fuel the heater the gas remaining in the bottle expands (remember fuel atomisation is much like expansion) by taking heat from the actual bottle causing it to drop in temperature.
You can of course short cut this by just hitting the valve off the bottle with a sledge hammer but I thought the safe way would be best although if you do it this ay the affect is quite interesting to say the least.
Why does it happen.
Carbs are isolated from the engine on big rubber manifolds so that the intake charge of air is as compressed (assuming NA) as possible. Thats why it happens.
How can you stop it.
Heat the carbs it doesn't happen but on bikes like the GPZ900 the carb heaters took 9BHP, a fair amount.
Toss up between power and rideability in the cold. |
Thats a long winded and not a very factually correct explanation, Kickstarts was right
Carb icing is when ice forms in the carb(s) initially affecting the idle circuit, the ice is moisture taken from the incoming air which gets supercooled by the carb venturi effect, the petrol has nothing to do with it other than it can't flow. It can happen anywhere from 5-6C (sometimes more) down to freezing point in damp air (if it's freezing then you have next to no moisture in the air so it's not so bad surprisingly), that's why it's more prevalent in early winter and late winter/early spring. The faster you go the cooler it gets the more ice you get around the idle jet area and eventually it blocks. You slow down come off the mains onto the idle but it's partial/fully blocked so the engine runs either really rough or just dies. You can get away with it just running rough for a bit until the latent heat from the engine melts the ice or if it stalls you have to wait for the ice to melt before it will start again.
Used to have an old GS Suzuki that could take up to half an hour to thaw out on a bad day, then just start and carry on as if nothing had happened.
Warming it up before setting out doesn't really help as if the right weather conditions are there and you haven't got heaters or additives then it will happen anyway, some bikes are more prone to it than others dependant on their layout, think yourself lucky if you haven't got a ramair Kwacker, they're notorious for it.
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| jonnay |
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jonnay
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| Kickstart |
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Kickstart
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| jonnay |
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jonnay
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| Posted: 22:25 - 28 Dec 2005 Post subject: |
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| sickpup |
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sickpup
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Joined: 21 Apr 2004
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Posted: 23:05 - 28 Dec 2005  Post subject: |
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| Bezzer wrote: |
Thats a long winded and not a very factually correct explanation, Kickstarts was right
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Why thank you.
| Bezzer wrote: |
Carb icing is when ice forms in the carb(s) initially affecting the idle circuit, the ice is moisture taken from the incoming air which gets supercooled by the carb venturi effect,
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Well you used 'Venturi effect instead of vacuum but the above agrees with me. I suppose we could say the dropping of the piston creates a low pressure area and as the inrushing air stream passes over the emulsion tube to creates a venturi causing a vacuum.
Remember the word supercool.
| Bezzer wrote: |
the petrol has nothing to do with it other than it can't flow.
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So the supercooling can only effect water and not atomised petrol?
| Bezzer wrote: |
It can happen anywhere from 5-6C (sometimes more) down to freezing point in damp air (if it's freezing then you have next to no moisture in the air so it's not so bad surprisingly), that's why it's more prevalent in early winter and late winter/early spring. The faster you go the cooler it gets the more ice you get around the idle jet area and eventually it blocks. You slow down come off the mains onto the idle but it's partial/fully blocked so the engine runs either really rough or just dies.
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And heres where we run into a problem with your explanation.
It also happens when bikes are on WOT. In fact if I remember the Kawasaki custom thing that was the first (japanese) bike in the UK to be recalled for carb mods it only happened at WOT.
Incidently this disagrees with Kickstarts explanation
| Kickstart wrote: | This results in the carb being so cold that the moisture in the intake air starts to condense and freeze, normally around the attomiser tube. |
a hell of a lot more than mine so why am I wrong and he's right?
| Bezzer wrote: |
You can get away with it just running rough for a bit until the latent heat from the engine melts the ice or if it stalls you have to wait for the ice to melt before it will start again.
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Please refer to the why does it happen bit on my post.
| Bezzer wrote: |
Used to have an old GS Suzuki that could take up to half an hour to thaw out on a bad day, then just start and carry on as if nothing had happened.
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Should try an old 900SS.
| Bezzer wrote: |
Warming it up before setting out doesn't really help as if the right weather conditions are there and you haven't got heaters or additives then it will happen anyway, some bikes are more prone to it than others dependant on their layout, think yourself lucky if you haven't got a ramair Kwacker, they're notorious for it. |
Yes Kawasaki's are bad. |
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| HurtMePlease |
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HurtMePlease
Trackday Trickster
Joined: 16 Jan 2005
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| Posted: 09:24 - 29 Dec 2005 Post subject: |
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Nice posts sickup 
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Hear Thy Call..............................
Rs125 (97) <-Sold|Riding->ZXR400L2(92) Yamaha R6(01) |
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| G |
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G
The Voice of Reason
Joined: 02 Feb 2002
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| Ian (GPX) |
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Ian (GPX)
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Joined: 05 Aug 2003
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| Posted: 10:50 - 29 Dec 2005 Post subject: |
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I had this problem last year and the year before, decided to look into it over the summer of this year. Noticed on my bike that the carbs on it had water ways, so i got all the bit's to hook the carbs to my cooling system just before winter (Nov 2005) and since then I have not had a problem with the carbs iceing up.
Oh, bike is a ZX600R  |
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| sickpup |
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sickpup
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| Bezzer |
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Bezzer
World Chat Champion
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| Posted: 16:27 - 30 Dec 2005 Post subject: |
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I'm back 
| Quote: | None of the articles I can find explaining carb icing relate to Motorcycles, they all seem to be about planes and I agree they all say due to moisture. Thing is different things happen at altitude. |
Exactly, may be different heights, so even cooler, but it's still moisture in the air that freezes and blocks the jets, not the fuel.
There are loads of different "official articles" as you say relating to aircraft as it's a bit more serious when your engine cuts out a few thousand feet up  but there are also plenty of car and bike articles, some more official than others, that all confirm the same causes.
| Quote: | So the supercooling can only effect water and not atomised petrol?
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Yes, the freezing point of petrol is so much greater than water, if it gets that cold then it would be one big ice block from the water before petrol started to freeze. If the air temperature is freezing but dry you won't get the icing as Dodsi mentions from experience in an earlier post because there is little or no moisture in the air, so you're getting an extremely low intake temperature but the petrol still doesn't
freeze or even wax.
| Quote: | And heres where we run into a problem with your explanation.
It also happens when bikes are on WOT. In fact if I remember the Kawasaki custom thing that was the first (japanese) bike in the UK to be recalled for carb mods it only happened at WOT.
Incidently this disagrees with Kickstarts explanation |
No problem there dude, there's always an exception to the rule, people who have had it will tell you that the majority of times, perhaps even every time they've had it(my problems with various bikes were never a problem at high throttle openings even the cursed Sucksuki  ), it's when you come off the throttle that it dies/misfires. It doesn't usually happen at large throttle openings for the same reason that flowing water takes longer and lower temperatures to freeze compared to still water. The petrol is flowing and not giving the moisture time to build up ice and block the flow, the idle circuit is "idle" so thats gets the ice building up, you come back onto the idle and there's little or no petrol getting through so it runs rough/dies. In extreme circumstances, and we are talking about notorious Kawasakis here, the mains could start to ice up even when flowing causing problems.
I agreed that Kickstarts explanation was right because he stated it was all to do with moisture not petrol.
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| Kickstart |
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Kickstart
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Old Thread Alert!
The last post was made 20 years, 257 days ago. Instead of replying here, would creating a new thread be more useful? |
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