Carb Icing

[steve pegg]

Hi Ladies, Gentlemen,

Carb icing has been an ongoing problem since I have had the bike [1995] but due to recent weather now particularly annoying.

Tends to start at temperatures +5c and below ,obviously worse when in rain or drizzle. Symptons/ problem: begins with erratic running and will eventually freeze throttle slides in last position. Carbs have on one occasion been completely covered in ice and motor stopped. As an experiment I lagged the carbs as best I could, that helped smooth the running out but I still ended up with a stuck throttle.
The bike is a 78 500 Strada fitted with a J cam all in very good nick only non standard thing is that it has been fitted with a 350 airbox in a previous life which I realise could be a contributing factor.
So has anyone a 500 air box they do not need and or any ideas on solutions? [serious ones, please wait for summer is not an option, we do not have them].

Lastly is it just me with this problem?

Thanks Guys and Girls, Steve

[MickeyMoto]

Hi Steve,

I have never suffered carb icing on a Morini. I used to ride my Strada in all weathers and it was always impeccably behaved. Frozen throttle slides is worrying, carb icing is usually water freezing in the jets. My old XBR 500 was a devil for that on cooler mornings.

['It must be a .....']

Hi, I've often had carb icing on a road 500 5 speed but never on Mk I/II 500 Camels and they all had the same carb settings along with the standard airbox (same).
Although I once had the clutch cable instantly freeze on a Camel and was left with no drive!
Have fun, Ian

[Morizzi]

Hi Steve,

Carby's work a bit like a TX valve in a refrigeration system. As the fuel is "atomised" (not technically correct but you get the idea) some of it changes from fluid to gas due to the lower air pressure in the carby venturi. They need heat to do this and is is absorbed from the surrounds effectively dropping the temperature. TX valves can ice up if water gets into the system as Mickey has stated.

Try putting about 50ml of metho into the tank before you head off and see if that helps. Metho is hygroscopic and will deal with the water. 50ml is about 0.3% of a full tank and won't worry a thing. I only use it to stop the tanks from rusting as I live in a warm semi tropical climate. I have to go inland in winter to get down to 5C.

How does the water get in? Poor quality fuel from the supplier is one but every night as the temperature drops the air and fuel in the tank cools and shrinks. It draws in moist cold air from the surrounds through the cap vent. This moisture condenses on the cold inner tank walls above the fuel line then dribbles down.

Keep the tank full and it will get less moisture but it will still get some. There are lots of proprietary fuel conditioners that claim to help but just a dash of metho also works.

I can just imagine the rustling of unrest about alcohol in the fuel. Seals will rot, animals will fall over drunk after sniffing the exhaust, the earth will stop spinning, etc, etc, etc. In reality keep the dose down and you will not notice a thing. We have 10% ethanol in lots of fuel here. Funny how the bikes are all still running.

Good luck and please let me know if it helps. You never know I may be tempted to go somewhere cold one day.

Cheers

Rod

[steve pegg]

Thanks to everyone for the advice.
I to have a Camel which has been exposed to same if not worse weather and also did not suffer from icing. Fortunately the weather has now changed and I think I am now out of that area until later this year. Should I establish reason and solution I will put it on the forum.

Thanks, Steve.
One Moto is not enough!