All 2st Frozen Carb

05 WR250. Had it for a year. No problems. Starts real easy / runs great 50:1 pre mix.

Yesterday I went out on a trail with the Green Lane Crew in England. Full on ice & snow (unusaual for UK in this area). Bike started fine but as soon as we got going it felt like the choke was still on - wouldn't rev properly and eventually choked up altogether and stopped. Changed the plug & all was fine then it all happened again. If I stopped for 5 mins then it would start but as soon as we got going it would progressively choke up again. Some bystanders said it appeared too rich (50:1 I dont think so) some said the cold could freeze the carb preventing the air getting through thus sending neat gas into the chamber richening it up.

Given the total ice conditions, I never got to rev the bike properly - poodled along in 1st / second hardly above tick over. Dropped the clutch and revved whenever I could to clear it but like with the choke on, the engine flooded up every time i tried this.

Has anyone ever heard of symptoms like this before. Some on the ride said they had ??

Dont know what the temp was but it must have been several degrees below zero.

Check that the hoses from the carb doesn´t clog up with ice and snow. If so, draw them up into the airbox. When i go iceracing i isolate my carb with 4-5mm neoprene sheets. I have one piece on each side of the carb and cut it with a szissor or knife to make it fit as close as possible to the back of the cylinder/ reedvalve housing and cut it to reach the choke. I also make a hole for the fuel hose to get it close to the carb. I push the top of the cover up between the fueltank and frame to make it fit. The upper front side of the isolation is pushed in between the water hoses on the cylinder head to not let cold air in. I reach 120-130km/h on the ice and i´ve been riding down to -15celsius and never had any problems.

Johnny:sweden:

Hi Arkley,

Dunno if it's relevant, but I used to have a Suzuki 600 bandit that was so well known for having carb icing problems it had a free fix by suzuki, (not for me tho as I bought it 2nd hand and no service history) and whenever it was icy it would start fine and run for about 5-10 mins then just pack up and would not start at all, I think as you ride it, it gets even colder as you cause a wind chill factor with the freezing air blowing around the bike. I had to leave it at the roadside on really cold mornings and make my way to work, when I finished work and it was a bit warmer in the afternoon I would go back to the bike and it started no problem drove me nuts.

I'm in the UK and to be honest I don't think it was as cold then as it is right now. It could be a jetting issue with the really cold air as my 600 just stopped dead and would not run at all once it iced up.

Hope this helps

Regards Steve

my husqvarna sms125 08 reg

hiya mate.... im having exactly the same thing happening to my bike...... i am in the uk, birmingham.. its been bout -10 around here over the past week.. it is really bugging me now because i have no idea why its doin it.. can any 1 help

It's common problem on a liquid cooled 2-stroke in winter, the cold moist air cools even further as it goes through the carb venturi and as the air reaches it's dew point temperature, water droplets fall out of the air and freeze on the inside walls of the carb effectively choking off the air flow if allowed to continue.
In the old days (early 80's) of the air cooled engines there was usually enough warm air coming off the motor to prevent the carb from freezing. The problem now with liquid cooling is that the engine cylinder doesn't provide enough heat to the carb. I saw a World Enduro video from Sweden a few years back and the TM or GasGas team had a leather shroud that went around the engine cylinder back to carb to keep it warm.

Try it=)!

When i go iceracing i isolate my carb with 4-5mm neoprene sheets. I have one piece on each side of the carb and cut it with a szissor or knife to make it fit as close as possible to the back of the cylinder/ reedvalve housing and cut it to reach the choke.


Johnny:sweden:

what kind of premix are you using? i know that some of them, like 927, won't stay in solution at sub-freezing temps. you might try putting some tape over the front of your rads so the bike can more easily reach and maintain operating temps.

Palito is correct and it has nothing to do with fuel mix ratio...your carb is freezing due to the sub freezing, moisture ridden air that pass through the carb. Stationary, there is probably enough warmth to dissolve but add the speed that you are traveling, that -10 air is now being forced feed causing icing to your metering circuits/emulation tube etc.
You could try various additives but Johnnymanen is spot on and seeing as he is from one of the coldest parts of the world, l'd take his advice!!!
Blocking the airflow to the rads only aids in heating up the motor but your carb is still exposed to the elements once you are moving.

Have fun!!

Pre-heating the air going into the carb is the only true fix for this problem.

When the air speeds up the pressure drops and so does the temp causing the moisture in the air to freeze. Heating the carb itself at the intake side of the slide or heating the air box is the answer. A simple way would be to make a heat stove around the exhaust pipe and draw heated air from the stove into the air box.

hey johnny how about some pics!!

Cheers for the comments peeps. I reckon you must be right. I'll try a neoprene boot to keep the carb warm. It's not often this cold in UK. Like you say, when the bike stood for 5 mins it would then start - guess heat off the engine whilst bike at standstill was enough to thaw - get going again into wind & chill factor - freezes up again.

I´ll take some pics as soon as i´m at the garage!

I'm 101 / feet down most of the time - vid mins 13.30 / 15.50 / 20.53 / 24.40.

Look forward to seeing Jonny's pics as the carb issues took my mind of the enjoyment a bit. Still a blast though - snow on top of ice..



http://vimeo.com/18079321

You might throw a couple of the hand warmer packets in the neoprene boot.

As a kid we rode in below 10 F and would have trouble with the powder snow freezing on the air filter and choking it down. Then you would stop for a few minutes and it would melt off. By the time we would be done riding the air filter would basically be a block of ice.

I don't do any real cold weather riding but did anyone think of taking a Moose Racing winter elephant ear and modify it to fit the carb/fuel injection area ? I could see those hand warmers working pretty well in that setup or a set of hot grip leads..

Chow, Carl

Ok, here´s how my Neoprene carb protection looks. very simple, but it works perfectly. 5mm thick Neoprene sheets cut to fit!

Cheers for the pics - everything thawing now in the uk. If it happens again I'll def fit the boot. All seems to be working fine now warmer so guess must have been the cold & my lack of speed....doh..