Carb Icing

well I found high rev's just ment the bike sucked in more fuel due to the lack of 'unfrozen' air.. and a low rev's the bike just stalled due to not having enough umph to keep it going... And kangeroo'd when I pulled away.. rather scary on a 220kg bike.
So its all loose loose.. the best option is stop.. wait.. warm them up if you can... then carry on with your journey.

Looks like the GT has carb heaters.. though I suspect they ain't working. Something to look at this weekend..

[Spiderman]

After a disastrous start to my day where the bike just didnt want to fire, to me trying too many times and flattening my battery i've popped out and bought what seems like the neccesary bits.
1xSilkolene Pro FST
1xOptimate 3 charger.
1xSoldering iron (but thats to fix my heated grips)
At least if it wont start tomorrow i've got a charger to keep the battery alive. Not like this mornings fun and games of attempting to push start the bitch.

[northwind]

I think the cause of carb icing is something to do with fluid dynamics... When a compressed gas decompresses it gets cold, or something like that, and there's a fair bit of that going on in carbs. But that could all be cobblers

Mine ran like it was full of rocks on the way home, I'm inclined to blame carb icing since it had an actual layer of ice all down one side... First time I've ever had it too. It got much worse as the bike heated up, which was odd- at first it was fine but a little hesitant, then it rode fine but wouldn't idle, then it started missing in the middle rev band but idled fine. I was never able to get it right up the revs from that point, i was almost home. The other thing was it had a really bad pick-up, just like you get if the idle speed's too low.

So I'm blaming carb icing, but at the same time the high-rev problems were the exact same as what I got when I was running badly lean, and I reckon I've been running a bit lean for a while- the colder it is, the leaner you get, so it could be partly that. I always use Optimax or BP Ultimate anyway ut I reckon I'll be looing for some FST Pro at the weekend.

Carb icing its self changes the presure in the carb's which will affect the fuel mix of the bike, plus the freezin water droplets in the air mix forming on the inside of the carb doesn't help. Once it starts icin it just seems to get worse. the only thing that seems to really make it better is stopin and waiting. Just 5 mins seems to do· If my carb heaters don't work I'll be usin Sid idea of redirecting some engine heat in to the air box to try and get the air temp up.

[dirtydog]

used to get carb icing on my 2000 sv happened all the time used fst had no problems after that with it. not had any problems at all on my k2

[northwind]

Colder today, but it went fine- I took out the tank spacers to richen the fuel mix, and now it's just a tiny bit hesitant in places, but actually goes. Which is nice.

Got my carb heaters going this weekend, though I think maybe one is still playing up. Turned out the earth had formed a layer of rust and was not working.
I still got a little bit of trouble this morning but when I pull over and wait maybe a minute or two, all is fine. The other trick is turn the engine off at the lights. The super unleaded fuel from BP seems to make no difference, I do have a plan to help combat this problem.... that may even work on all carb'd bikes.

Right.. if I take a heated jacket kit like this:

link to ebay auction

Wire it up so that it lines the inside tubbing of the air filter, surley this will warm the air going into the carb not to much. Enough to stop the air dropping below freezing.
Anyone think this is a good idea?

Right found a reason why my fuel treatment doesn't work:

Pro-Boost only has a minor effect on carburettor icing; it is primarily an octane booster. Likewise, Pro-FST
has a minor positive effect on octane rating, but it is not a good idea to use it as an octane booster, because it's a carburettor de-icer!

The bloke who sold me the bike gave me the wrong fuel treatment! Doh!

And taken from the Silkolene website:

Pro-FST: British Technology Engineered in Britain.

Pro-FST (Fuel System Treatment) was developed in 1992 following an unofficial request from Kawasaki Motors (UK) Ltd., for something that would deal with the particularly British problem of carburettor icing in damp, cold weather. (It was also specifically a motorcycle malady. Cars have room for heated air intakes.) KMUK were harder hit at that time than the other 3 big Japanese MIC manufacturers, because they sold a lot of 'GT' models to dispatch riders, who obviously covered a lot of miles in all weathers; there were also a lot of complaints from the 'off road' fraternity.

The problems were:
Poor starting, irregular tick-over, sticking throttle, stalling at Iow speed, re starting problems, high fuel consumption and general rough running. What caused this was the formation of ice crystals in carburettors, blocking slow-running jets and jamming throttle slides.

The reason why the ice formed was because carburettors act as refrigerators!
The drop in pressure across the jet bridge plus the heat absorbed by evaporating fuel drops the temperature by several degrees; this will freeze out any moisture in the incoming air, especially when it's only a few degrees above zero to start with. In really freezing weather there is no problem, because once the air temperature drops below zero, the water drops out as frost, leaving dry, cold air.

The cure:
is to add something to the fuel which will dissolve the ice as it forms, without upsetting any applecarts: no fuel system corrosion, no ill effects on octane rating and so on. KMUK actually hired an environmental
test chamber for the trials, and sent videoed results to their masters in Japan, who had always refused to believe there was a problem!
After a few tries we came up with the answer, later sold as Pro-FST. 1% of this would
deal with normal icing conditions, and 2% would handle the worst they could throw at it. (Fog at 1 degree C) Apart from something that dissolves the ice, we included a synthetic low-temperature lubricant to lubricate carburettor bits and to act as an upper-cylinder lube to cut down cold-start ring and cylinder wear. Also, because some motorcycles are 'weekend only' transport, a touch of anti-corrosion additive was included to look after the top ends of engines standing idle in damp garages.