The Good The Bad & The Ugly

[utopia]

Originally Posted by Mr Gazza

I suppose it was bound to happen eventually, but for the very first time I disagree with Utopia, Oracle of wisdom and common sense.

Thanks for the sentiment anyway.

To be honest, I've probably let myself down here as I was guilty of quoting received information rather than my own experience.
I should really have said, my electric heaters don't eliminate the problem, though they may well help a little, and I've heard that the oil fed ones aren't any better.
......until now, that is.
As a result of your comments, Gazza, I'm now beginning to reconsider them.
Though the extra plumbing is untidy. Pro.fst is certainly neater.
Anyway, the plot thickens.

Oddly, my Dommie doesn't seem to suffer, despite 650cc sucking through a single (electrically heated) carb.

[Flip]

The only thing I find with the oil heaters is that it takes a while for the oil to warm enough to actually do it's job properly and so it's a kind of yes they work but not right away when you want it to.

Whereas I would think the electric heaters would work straight away as they always did on my SRAD GSX-R750 which ran great in all weather- not saying my Monster's ever been a problem really though but you get used to things and 'ride around' them eventually.

[Dirty]

Probably a really stupid question but I've come from a background of old cars (mainly old carbed Fords) and I've never heard of carb icing. How did they approach the problem or is it due to car engines being generally more enclosed than a bike?

[utopia]

I'm no expert and it was a new experience for me too, when I got the monster.
But I would say that its probably dependant on many factors, including the enclosed environment of a car engine. I seem to recall having seen collector plates which can direct exhaust heat to the inlet on a few old cars too.
However, the main factor is probably the size of the cylinder and hence how hard it can suck through the carb, and this lower pressure causing atmospheric moisture to condense and freeze around the jet.
In a multi cylinder engine, the suction from each cylinder is much less.
Seems to manifest itself most often after a stretch of constant throttle followed by slowing for a junction.
For some reason, monsters seem to be particularly prone to it, while I'm not aware of it being so common in other big twins.

[Darren69]

Same problem for the 900SS I had, although I'm not sure if my 750ss was the same, I can't remember that far back. The oil heated carbs were not fitted to my 900ss but I got some fitted and it helped a bit but would still ice on long stretches at speed. I ended up puting a carbon plate in the frame to shield the manifold and one on the oil cooler with holes drilled that would make the oil run a little hotter. This along with Pro FST did virtually cure the problem.
Then I went and got a FI duke so no problems any more.

Oh yep, still on the carb icing front I used to have terrible trouble with that on my old 600 but never on the 900. It's generally particualry bad in damp conditions just above freezing point, cold moist days and in freezing fog. The venturi effect of the caarbs acts like a little refrigeration unit and drops the cold air to below freezing air causing the moisture in the air to freeze. Once the temperature has really dropped below freezing it goes as the moisture freezes out of the air anyway.

At first I used the tried and tested Silkolene ProFST but it's pricey (though it works a treat) - cheapskates like me though use isopropyl alcohol - surgical spirits - as it does the same thing with no noticeable adverse effect for much less money.

Of course if you get a 900 or one of those newfangled modern fuel injected ones the trouble goes away!

[Mr Gazza]

My claims for the oil fired carb warmers were not intended to be dismissive of anyone elses experiences.
The effects of carb icing, and indeed of the effectivness of the warmers seem to be very varied.
I can only conclude that carb icing requires some very specific conditions, and may well be more due to the enviroment that the machine is ridden in, rather than the machine itself, as to whether or not the warmers have any effect on the problem or whether icing is more likely to occur i the first place.

Most of the proper cars that I drove about used to have a "Summer" and "Winter" position for the air intake trumpet, or a diverter flap. This simply drew air over the exhaust pipe in the Winter.
This begs the question. Do the carb warmers warm the air or fuel?

A crowd of us watched in amazement outside the pub, one chilly night, as a strange white frost grew on a leaky petrol pipe on some old English bike.
I am not exactly sure if the "frost" was frozen petrol or water.

I am guessing that what was happening was that the evaporating petrol was robbing the air of it's little heat energy in order to evaporate, and condensing the water in the process which appeared at least to freeze?

So not sure if the source of the Monster carb icing is the fuel or the air ??