Carb icing?

[bigchris]

Is there anything i should be doing to the carbs on my curvey to prevent them iceing up now the winter cold has set in?
Over the last few days when i start the bike it seems to run on one cylinder for 3-5 secs before the other kicks in?
It only seems to be doing this since the cold weather set in?

[toxic]

:smt109

wynn's dry fuel or that silkolene stuff or chop the bike in for summat with fuel injection

[andrewsmith]

Silkolene Pro FST Chris.

Which cylinder seems not to be firing?

[Berlin]

That's not carb icing. You'll usually find the carbs ice after a little while when riding, especially on frosty mornings. It happens due to "latent heat of evapouration (or vapourisation)". Oh! Get me! :) Thats a technical way of saying that as the liquid fuel vapourises in the carbs, it draws heat in from the environment which cools the surrounding metal, leading to icing.

Curvy carbs have heaters in them to prevent this happening but they can be overwhelmed as has been mentioned on the forum.

The stutter you have on start up is just the bike coming on song. A squirt of WD40 on all of the wiring, should work wonders along with making sure your carbs are balanced, plugs are good, your choke cable isn't sticking and all the other usual winter checks. For the first couple of seconds its just sorting itself out and getting warmed up. If it gets worse, it might be worth clearing the pilot jets out in the carbs too. But again, as long as its not longer than a couple of seconds, I wouldn't worry.

C

[bigchris]

[QUOTE=Berlin;2421000]That's not carb icing. You'll usually find the carbs ice after a little while when riding, especially on frosty mornings. It happens due to "latent heat of evapouration (or vapourisation)". Oh! Get me! :) Thats a technical way of saying that as the liquid fuel vapourises in the carbs, it draws heat in from the environment which cools the surrounding metal, leading to icing.

Curvy carbs have heaters in them to prevent this happening but they can be overwhelmed as has been mentioned on the forum.

The stutter you have on start up is just the bike coming on song. A squirt of WD40 on all of the wiring, should work wonders along with making sure your carbs are balanced, plugs are good, your choke cable isn't sticking and all the other usual winter checks. For the first couple of seconds its just sorting itself out and getting warmed up. If it gets worse, it might be worth clearing the pilot jets out in the carbs too. But again, as long as its not longer than a couple of seconds, I wouldn't worry.

Righto, cheers pal, i did notice the choke cable has gotton quite stiff. Is it a pain to lube? I will give all the wiring a good coating in wd40 aswell.




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[yorkie_chris]

It is easy to lube, get nozzle of some spray grease into splitter box which is on RHS of front carb. Also inside switch gear where cam is... it will work its way down the cable after a while.

You can buy isopropanol on eBay, cheaper than pro FST. 100ml per 10l of fuel is enough to sort it.

[bigchris]

That's not carb icing. You'll usually find the carbs ice after a little while when riding, especially on frosty mornings. It happens due to "latent heat of evapouration (or vapourisation)". Oh! Get me! :) Thats a technical way of saying that as the liquid fuel vapourises in the carbs, it draws heat in from the environment which cools the surrounding metal, leading to icing.

Curvy carbs have heaters in them to prevent this happening but they can be overwhelmed as has been mentioned on the forum.

The stutter you have on start up is just the bike coming on song. A squirt of WD40 on all of the wiring, should work wonders along with making sure your carbs are balanced, plugs are good, your choke cable isn't sticking and all the other usual winter checks. For the first couple of seconds its just sorting itself out and getting warmed up. If it gets worse, it might be worth clearing the pilot jets out in the carbs too. But again, as long as its not longer than a couple of seconds, I wouldn't worry.

C

Cheers pal, i did notice the choke cable was a bit stiff. Is it a hassle to lube?
I will give the wiring a good coat of wd40 aswell.

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[keith_d]

Is there anything i should be doing to the carbs on my curvey to prevent them iceing up now the winter cold has set in?....

Buy a pointy??

[toxic]

Buy a pointy??
. . . . . :winner:

[Berlin]

What, so you can have one of the 27 sensors pack up when the salt gets into them? ;)

C

[fastdruid]

Worth mentioning that the sensor for the carb heaters can be badly located, if its touching the frame or hidden out of the wind it can be a few degrees above ambient and fail to turn the heaters on.

It is the small pound coin shaped thing with (IIRC) two yellow wires up on the RHS near the headstock, around the area of the coolant tank filler.

Druid

[embee]

It's not at all unusual for them to fire up on one cyl for a couple of seconds, especially with winter fuel.

Fuel changes throughout the year, in winter it is more volatile for easier cold starting. This means that when you stop a carb engine from fully hot, more fuel will evaporate from the carb bowls and they will need to be refilled before it runs properly. Inevitably one carb will fill faster than the other so it fires up on that one and a couple of seconds later the other will chime in as it fills. As long as it is only a few seconds it's nothing to worry about (and nothing much you can do about it anyway). FI doesn't suffer this because the system is effectively sealed once the ignition is off so it can't evaporate and remains full of fuel.

As YC says, the active ingredient in "anti-icing" additives is usually IPA, which attaches to the water molecules and inhibits the ice formation. Put "IPA" or "Isopropanol" in an ebay search and see what you find. Use it in the amounts as YC says. The carby SV is quite prone to icing.

In theory it can degrade rubbers used in normal petrol based sytems but they are reasonably resistant to low percentages so it's not an issue in practice (and normal pump fuel is allowed to contain a few percent alcohol anyway).

[yorkie_chris]

That's Isopropyl Alcohol... NOT Irish Pale Ale!!

[fastdruid]

I actually found it's *not* that prone to icing, as long as the heater sensor is in the right place. If its wrong by resting on the frame then it works perfectly on start up but then fails after ~30mins as the frame warms up.

Druid

[yorkie_chris]

I hung the sensor on mine right out in the wind blast one year, no problems. Year after, had problems in bad weather so wired them to come on with the ignition... still problems... bought some isopropanol ... no more problems.

[embee]

That's Isopropyl Alcohol... NOT INDIAN Pale Ale!!

One is for the bike, the other is for the rider, just don't mix them up! :smt030

[deejpj]

can someone post up a picture of the sensor & where its located as i cant find it on my bike. Its a UK bike so should have one