Weber Carb freezing.

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jrose

jrose

Active Member
Posts
102
Location
Basildon, Essex
Morning all, not the frosty weather has arrived I'm fully expecting the annual shenanigans with my weber carb on my 2 1/4, I've been in contact with my mate down the Falklands, I was down there for a 6 month deployment last year, he drove his series 3 through the winter with no snags at all, it regularly hit -15 whole I was down there, he said he was running on an SU carb and had no problems at all, do any of you use them, is it worth the swap, he's sending me one over.
 
Fit a radiator muff(or plastic bag) it’s the damp cold air freezes the petrol in the throttle body.
Are you running the standard air filter?
 
I run an SU, did my own custom conversion.
Always found in freezing temps it would stall at a junction near home like clockwork, leave it a handful of seconds to defrost then be fine for the rest of the day
 
jrose said:
Yeah, the original oil bath filter, done an oil change on it in the summer, quite dirty inside. I've looked at radiator muffs, might give one a try.
Click to expand...
Normally the exhaust keeps the carb warm(except S1 as exhaust on other side)
And stops the ice forming. That muff warms the engine bay up preventing the ice forming.
 
I doubt if the petrol is freezing, petrol freezes at something like -40 degrees. If there is some moisture in the carb, that will freeze. I had a motorbike years ago that had this problem, it wasn't petrol freezing it was the jet holes shrinking a bit in freezing weather.

Col
 
I always understood carb freezing to mean when the body gets a white frost covering which chills petrol to the point out doesn't vaporise properly which means the air/fuel doesn't mix well for a good bang in the cylinder
 
The damp cold air get sucked into the carb causing the freezing. This in turn blocks the jets. You then get symptoms of fuel starvation & cuts out. You then pop the bonnet & in them few moments the heat from the engine melts the ice. Normally leaves people wondering what is wrong as it will start straight back up again.
Just putting a muff on restricts cold air & allows the filter to use the engine bay heated air.
There is a conversion for a S1 filter. Will see the motor next week for photos if needed
(Early Kawasaki ninjas were prone to this due to ram air system)
 
The freezing is when damp air just little above 0 deg goes through the carb, the drop in pressure through the venturi plus the vaporisation of the petrol freezes the water. As said above it blocks the jets and can stop the engine. The cures are heating the air - put the intake by the exhuast, and heating the carb body - usually conduction from the manifold but aircraft use engine oil. A home made fix is to put a tube on the air intake to right close by the exhaust manifold
 
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