Carb Ice?

dwelby101

I took my bike out yesterday just before the weather went from really warm and dry to the biggest downpour i have ever experienced... I ride a Suzuki GSX 400 Impulse and i noticed that the performance of the bike as soon as i took it out was pure sh1te, it was like the engine was running with the choke fully on, felt like the engine was flooded and was going to cut out. I had to keep the revs high (3000 rpm) while standing at traffic lights to ensure that when the lights turned that the bike wouldnt just die. I done a bit of research about this and found this http://faq.ninja250.org/wiki/What_is_carburetor_ice%3F
It explains the cause and effect of this "carb ice", I put it down to the fact that the humidity before the sky opened yesterday must have been really high giving me this weird effect. Has anybody else experienced this? stories?

Wossack

highly doubt it.. they're be no encourging it to keep going if it was icing imo

bad fuel?

Mr Sheen!

dwelby101 wrote: »

I took my bike out yesterday just before the weather went from really warm and dry to the biggest downpour i have ever experienced... I ride a Suzuki GSX 400 Impulse and i noticed that the performance of the bike as soon as i took it out was pure sh1te, it was like the engine was running with the choke fully on, felt like the engine was flooded and was going to cut out. I had to keep the revs high (3000 rpm) while standing at traffic lights to ensure that when the lights turned that the bike wouldnt just die. I done a bit of research about this and found this http://faq.ninja250.org/wiki/What_is_carburetor_ice%3F
It explains the cause and effect of this "carb ice", I put it down to the fact that the humidity before the sky opened yesterday must have been really high giving me this weird effect. Has anybody else experienced this? stories?

Don't think you would be getting carb icing at the temps we were having yesterday.

dwelby101

leppla wrote: »

Don't think you would be getting carb icing at the temps we were having yesterday.

I was thinking the same thing but whenever I take it out and the weather is really heavy it seems to behave like this, that been said it only acts like this on short trips around town if i take it for a long spin at higher speeds it goes fine, my thinking was at higher speeds the engine runs hotter getting rid of the "ice" problem, am i wrong?

Wossack

whats the temp like - is it always midway on the gauges, even in the recent weather? does the fan ever come on?
the carbs are quite finicky on the gsx400's afaik.. oft resulting in them running really rich pretty much all the time

have a look on 400greybike.com

Hotblack Desiato

No way it was carb ice, the worst air temp for that is about 4C

Sounds to me you have a problem with the bike running too lean* when cold. Manual choke? If it has the wrong carb needles or jets, it might run fine at wide open throttle but run like crap on part throttle.

* or maybe too rich - warmer air is less dense which richens up the mixture on a carbed bike. But then the problem would get worse when the bike warms up, not better, as a cold engine needs a richer mixture.

hobochris

When was the last time your clearances were done and the carbs were balanced? unless you were riding in a freezer it wasn't carb icing (carb icing usually happens at temps close to or bellow freezing).

Hotblack Desiato

Carb icing can't actually happen if the air is below zero - it can't hold any moisture.

If it's only just above freezing, it can hold very little, so you might get a bit of icing but probably won't notice

If the air is warm, it can hold lots of moisture, but the carb won't get cold enough to freeze it.

Usually about 4-5C air temp is the danger point.

The freezing happens because not only is the carb sucking lots of cold air through it, it is evaporating petrol which cools the carb body (latent heat of evaporation) and under the wrong conditions it can go below freezing point.

dwelby101

it might run fine at wide open throttle but run like crap on part throttle.

I took it out again today and noticed that it was fine as throttle 1/3 and 3/3 but at 2/3 middle throttle it was very wooly I had the carbs cleaned about 4 - 5 months ago so they should be calibrated correctly, i did however let the fuel run a bit low at the weekend so maybe im getting some crap stuck in one of the jets, im guessing a fresh tank of petrol from a well known station (not some random shop in the middle of nowhere) and a good hard ride and she'll be good as new. hopefully the weather will hold out over the weekend!

Hotblack Desiato

Get a bottle of STP Fuel System Treatment in the silver bottle. Costs about 15 euro but you only need to use about a quarter of the bottle. This is the best stuff around for removing crud, I run a treated tankful of petrol through the bike once a year and it is worth doing. This stuff is way more effective than Redex.

Hopefully that will sort it. If not, next thing would be to check all the adjustment screws are the same on each carb and then balance them. After that, you could be looking at worn needles or jets, or a holed carb diaphragm maybe.