gwd Posted March 26, 2013 Report Share Posted March 26, 2013 Hi, looking for some help or info on carb freezing, I have a 2011 sherco 290 with a dellorto phbl 26 fitted, I was out on the weekend and the throttle stuck open 3 times, it didn't do it while I was riding the bike, it did it when I gave the bike a quick rev after I had been running about on it for around 20mins, once I got it to cut out I looked at the carb and it had a coat of frost over it. I let the bike sit for 5 mins, then try to start it again and it was perfect, at this point the frost had gone from the carb, 20mins out on the bike again and the same thing all over. it was my 1st time out on the bike and was just toting around in low revs, when I gave a quick couple of revs to the bike it was out of gear and prob a higher rev than when I was riding it. the 3rd time it did it was after I washed it at the garage then brought it home a few miles on the trailer, I dryed it of at the house took it along the street came back gave I couple of revs and it did it again. the temp was around 0/-1 all day and prob had a wind chill of even lower. any help would be appreciated. Quote Link to comment Share on other sites More sharing options...
0007 Posted March 27, 2013 Report Share Posted March 27, 2013 Well I know a bit about it Your carburetor will through evaporative cooling be a few degrees cooler than the air temp At 1 degree c there can still be substantial moisture in the air So the carb is below 0 and the moisture in the air freezes on contact Well below 0 it doesn't happen as the air is much drier It's hard to stop, you cannot jet it away but you can wrap the carb and try to get engine temperature to it Snowmobiles run coolant through the carb body, petcock to turn it on and off Outboards have electric carb heaters Not an easy fix Quote Link to comment Share on other sites More sharing options...
copemech Posted March 27, 2013 Report Share Posted March 27, 2013 I have never had a carb freeze up on a trials bike, yet I hear it happens. LOW throttle openings create higher venturi cooling, thus more temp drop accross the opening in the carb. This temp drop can be great like 30F, and I have had carb ice on a 60F day in high humidity conditions, in an aircraft! The ice can make them loose power, sputter and such on takeoff! Not a good feeling! Quote Link to comment Share on other sites More sharing options...
timp Posted March 27, 2013 Report Share Posted March 27, 2013 (edited) In icy conditions we tend to start the bike and get it warm(till the fan cuts in) then stop the bike. This lets the heat radiate from the engine to the carb. If you keep it running the cold air getting dragged in doesn't let this happen. Some older Shercos (a lot older than yours) had to have a stronger slider spring in the carb as it didn't return the slider properly. Also some riders cut a bit off the spring to make the throttle lighter to turn. Perhaps yours has been done like that. Rather than just using low revs use all the revs to keep things moving. Edited March 27, 2013 by timp Quote Link to comment Share on other sites More sharing options...
scraggydog64 Posted March 27, 2013 Report Share Posted March 27, 2013 On my old Montesa I made a piece of plywood to shield the side of the carb. This directed heat from the rear of the cylinder and kept the wind off it. Only had to use on occasions when the temparature allowed the carb to ice up. Didn't look very good but did the job. Others used to use duct tape. Quote Link to comment Share on other sites More sharing options...
wobblenorbed Posted March 27, 2013 Report Share Posted March 27, 2013 Hi, this happened to a friend of mine on a child day turned out there was some water in the air box ! When the air box and filter were dried out it ran perfect all day in minus three degrees c. Quote Link to comment Share on other sites More sharing options...
ham2 Posted March 27, 2013 Report Share Posted March 27, 2013 Birra cardboard with baco-foil wrapped around it makes an easy shield just like scraggydog suggested, I used cardboard 'cos (I'm cheap) it's easier to trim and you can stuff it in place without fear of chafing (ooh!) on anything vulnerable. Quote Link to comment Share on other sites More sharing options...
slack Posted March 27, 2013 Report Share Posted March 27, 2013 Hi gwd,i had this problem a few years ago,so after trawling through all the forums came across one that suggested to use SILKOLEAN FST PRO FUEL ADDETIVE . this sorted the problem,so know in the winter months i add it to my fuel and no more carb icing. Quote Link to comment Share on other sites More sharing options...
suzuki250 Posted March 27, 2013 Report Share Posted March 27, 2013 http://www.opieoils.co.uk/p-809-silkolene-pro-fst-fuel-system-treatment-for-petrol-engines.aspx Quote Link to comment Share on other sites More sharing options...
bigfoot Posted March 27, 2013 Report Share Posted March 27, 2013 I'd give the carb a good clean to make sure there is no water in it. I ride regularly in cold conditions and have only had frozen carb problems when there's been some water in there. It happened the other day in fact so I quickly cleared the carb and it was fine again all day. Quote Link to comment Share on other sites More sharing options...
rogboy Posted March 28, 2013 Report Share Posted March 28, 2013 Hi there I have done a lot of green lane and trials over the years in all sorts of weather on all sorts of bikes,and have had this problem many times.I found for a quick fix is an old piece of inner tube with a hole in it stretched around the carb and held with some tie straps work a treat.Try it Good luck Roger Quote Link to comment Share on other sites More sharing options...
telecat Posted March 28, 2013 Report Share Posted March 28, 2013 Seconded on the FST Pro. We had it years ago on a REV50 added this stuff in and used it since with no icing. Quote Link to comment Share on other sites More sharing options...
gwd Posted March 28, 2013 Author Report Share Posted March 28, 2013 Hi, thanks for all the helpful replies, I will order a bottle of fst pro and give it a try, also going to give the carb and air box a clean out tomorrow just to make sure there's no water in there. hope to get out this weekend and see how it goes, think the weathers still going to be cold so should be good to try some of the tips. thanks again. Quote Link to comment Share on other sites More sharing options...
ham2 Posted March 29, 2013 Report Share Posted March 29, 2013 Looks like the weather's going to be perfect for carb' icing conditions for the next few weeks according to the forecasts Quote Link to comment Share on other sites More sharing options...
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