From: trsajo@eua.ericsson.se (Anders Johansson)
Subject: Re: Winter Riding Questions
Reply-To: trsajo@eua.ericsson.se
Organization: Ellemtel Telecom Systems Labs, Stockholm, Sweden
Date: Mon, 16 Nov 1992 14:47:03 GMT

In article 3734@gandalf.ca, wardman@gandalf.ca (Russel Wardman) writes:
> In <4806@equinox.unr.edu> edh@wheeler.unr.edu (Ed Hackett) writes:
> 
> >In article <1992Nov9.142841.29479@gandalf.ca> wardman@gandalf.ca (Russel Wardman) writes:
> >>In <124510145@hpfcso.FC.HP.COM> jld@hpfcso.FC.HP.COM (Jeff Deeney) writes:
> 
> 
> >Actually, carb icing is only a problem when the temperatures are
> >above freezing.   The problem is caused by liquid water freezing
> >out in the venturi due to the cooling effect.  If the temperature
> >is below freezing, the vapor is already frozen, so it passes right
> >through.  The most common tempreratures for icing are between 70
> >and 32 degrees F.
> 
> >The carb on most bikes sits behind the engine, so it should recieve
> >enough  heat to keep it above freezing.  Carb ice is a funny thing.

	The Swedish Army has a nice solution to this problem:
	Standard winter equipment on their 250 Husky Automatics (air-cooled 
	Off-roaders) is a specially designed rubber cloth mounted as an 
	upside-down U over the carburettor, leading hot air from the back of
	the cylinder to the carburettor. The cloth is designed to reach from the 
	top of the gearbox on one side to the other, and from the back of the 
	cylinder to the front of the airbox, completely covering the carb.
	It is made of about 4 to 5 millimetres (about 3/16 inches?) thick rubber.
	There are a few holes and lids in the cloth for engine-mounts, 
	gas-wire, gas-hose, choke, etc. Works fine!

	They also run frame-mounted skis on these bikes, and un-studded tires,
	but that's another story...

> >Some intake designs ice up much worse than others.  If you have
> >trouble, like the Weber tuning manual says: the only way to
> >tell is to "suck it and see". If you do have a problem, a bit of
> >foil or something to direct more heat may help.
 
> What you say makes sense, but the icing that I have had trouble with
> was in the bowl, on the float needle. This of course resulted in flooding
> problems. I'd be careful about keeping my tank full to minimize condensation
> but still have the problem. Adding gas line anti-freeze to every tank, to
> stop the moisture build up, cured the problems for me. I recommended the 
> av gas because I know pro ice racers who use it, and I think they use it for
> this reason as well as the higher octane. I've never used it myself, and
> haven't decided if i'll try this winter or not.

	I also run anti-freeze in my gas, but to be shure, I manufactured my own
	rubber-cloth to cover the carb. This seems to have the desired effect.
	(It works, even though the '90 KDX200 is water-cooled)
	
	My experience tells me that the anti-freeze usually has more effect than
	the rubber cloth, but that they combine nicely.

	However, I've got one worry: how to protect the different over-flow
	hoses and such from freezing? It always seems like I end up having a
	bunch of hoses ending in a block of ice below the engine...
	On the KDX it doesn't seem to matter that much, but on the TT600...
	Especially when the ventilation hose for the sump-pressure froze,
	it would start to leak oil all over. Not to mention lack of idle.
	(When it got REAL snowy, the damned beast sucked in snow somewhere,
	causing the high-speed carb vacuum throttle to lock on WFO .
	No anti-freeze in the world would help then. :-)

	The obvious solution is to reroute these hoses, but to where?
	And what if I reroute an overflow-tube upwards under the tank for example,
	would the J-shape of the hose affect carb performance (fuel/water/dust
	getting stuck at the lowest point?)?


Anders Johansson, 
KDX200 (With studded tires! 350 studs in each tire, and 1/4 inch reach on each of them)






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