Carb Icing?

[synaptyx]

Ok, I've heard this term a few times recently. Being a tech-n00b I'm not sure of the technical reasons for it happening, other than it happens when it's very cold, like today:
I left the house this morning with the engine running fine. I got about half a mile when the engine spluttered and died at the lights. It would restart on the starter, but would die immediately if the revs went below 2500-3000rpm. At low revs the engine felt rough and vibrated a bit. How do I tackle the problem other than by walking to work?

Cheers!

(I get the feeling I put this in the wrong place - could some kind mod move it for me please? ta!)

[Kickstart]

Hi

Does sound a bit like carb icing, but I have only experienced it after travelling at a reasonable speed for a while. Normally you will find that once you get caught in traffic and have ridden slowly for a couple of minutes the problem goes away.

It would also surprise me if a fully enclosed bike that is effectively air cooled would allow the carbs to get cold that quickly.

Carb icing is caused by the air rushing through the carb taking the heat from it (aided by the amount of heat that the fuel takes from the jets as it is drawn out), with the result being the carb getting very cold and freezing any moisture in the air, which is a problem when that moisture is deposited on the inside of the carb as it freezes as it tends to block the jets.

Solutions? Go slowly everywhere (less heat taken from the carb). Go fast everywhere (more jets in use at higher throttle / revs, but that just delays the problem and might result in the mixture getting dangerously lean). Reroute the airbox intake to draw in air from a warmer area. Fit some kind of carb heating system. Blank off part of the radiator to get the engine area to be hotter (not enough to cause the engine to overheat). Change the brand of fuel you are using (the amount of heat taken by the fuel is partly dependent on the additives used in that fuel). Use a fuel additive designed to prevent carb icing (there are quite a few including one from VW for the old Beetle, but no experience of any of them).

I have had carb icing issues on my old FZ750, plus on the MBX125 and also my Aprilia Futura, but normally in far colder weather than we are currently experiencing. The FZ would start to suffer after 2 miles or so of dual carraigeway riding, while the 2 strokes only suffered after 20+ miles at speed (Mansfield to Derby on the A38).

I would say that it is more likely the problem you are suffering is something else than carb icing. Maybe a blocked needle valve overfilling one of the carbs and flooding the engine (just a guess, could be something else).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[synaptyx]

Excellent, cheers Keith!
It only happens when it gets down to 2°c or less, otherwise the bike runs fine. Thanks for your suggestions, I'll look at fuel additives as I'm too technically incompetent to do anything else. I'm using Esso unleaded (the petrol station is just round the corner). Speed wise it's all 30 limit, so the max I'd be doing is 30-35Mph (naughty me). Anybody recommend an additive?

[Kickstart]

Hi

To me 30~35mph sounds too slow for carb icing. That is the kind of speed that has allowed my bikes to recover from icing the carbs up.

Give one of the additives a try, which will either confirm that it is carb icing or at least mean you can check elsewhere.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[freestyler_onli]

Sounds like a problem i had.

Similar problem. Try to turn bike on 'COLD' message pops up of LCD screen. No power from ignition button. Sounds like a power drill being turn on and off quickly- revs wont increase with the throttle. Maybe battery-but all lights/dials light up normally-bike is only a few days old.

Is this all because the bike is cold-or is there a more obscure problem???

[stinkwheel]

[cagiva gezzer]

[freestyler_onli]

Will do- if i can get it there

Seriosuly though-i booked it in next week to have something fitted to it-ill get him to look then.

[kasandrich]

On the subject of carb icing, I got a good tip from a kawasaki dealer the other day.

The ER5, (so presumably the GPZ500 as well, and who knows what others), has an inline water filter, a little clear plastic tube about 4cm long, near the fuel tap, if you don't change it when servicing, it will clog up and cause carb icing.

They cost about £3.
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Richard

CBR1000FM

[map]

From my experience carb-icing symptoms are a bit like running out of petrol. The bike has no go. The revs start to drop and even dropping down a cog doesn't solve the problem.

Usually occured with me in the autumn and evening going down the motorway. Or down a straight when there was an icy wind - guess it's the wind-chill.

Sorted by just stopping for a bit (a minute or so) then restarting (before I found additive - see below).

Best thing I found was a fuel additive and stabiliser by Yamaha. Small black bottle (unless it's discontinued or being repackaged). Try Yamaha main dealer. Also very useful stuff to add if you park the bike up for a few weeks or so.

HTH
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