I'm looking for some frozen carb pictures.
Carburator freeze
- Thread starter Rubberhead
- Start date
A frozen carb freezes from the inside out, so getting a pic of it will be hard.
http://en.wikipedia.org/wiki/Carburetor_icing
The basics are the air speeds up, and cools down and drops it's moisture on the cold carb body, which is already super cooled from the air which cools as it speeds up going through it. Bigger carbs and less moist air reduce icing.. Or adding head is another way to reduce icing.
http://en.wikipedia.org/wiki/Carburetor_icing
The basics are the air speeds up, and cools down and drops it's moisture on the cold carb body, which is already super cooled from the air which cools as it speeds up going through it. Bigger carbs and less moist air reduce icing.. Or adding head is another way to reduce icing.
Pic
When I built the 500 kx 4 years ago I had bad carb icing problems. I was running a pod filter and went to do a jet change and realized the real problem was ice. I removed the pod and the throat of the carb was covered with a thin layer of sleet so to speak. It was blocking the air bleed holes that are there causing a rich condition.
I feel the Apt smarty is the only real fix because from what I have seen it don't utilize these air bleed jets.
When I built the 500 kx 4 years ago I had bad carb icing problems. I was running a pod filter and went to do a jet change and realized the real problem was ice. I removed the pod and the throat of the carb was covered with a thin layer of sleet so to speak. It was blocking the air bleed holes that are there causing a rich condition.
I feel the Apt smarty is the only real fix because from what I have seen it don't utilize these air bleed jets.
Carb Freeze
I was running a pod filter last weekend on my boys KX 250 and it looked like snow was getting past the pre filter. I put the stock air intake back on for this weekend hoping it would help. It only took about 20 minutes for the front of the carb to fill up with snow and slush. I am anxiously awaiting my smart carb. Has anybody had that problem with the pod filter? Will the stock intake help the icing issue? Thanks for the comments.
I was running a pod filter last weekend on my boys KX 250 and it looked like snow was getting past the pre filter. I put the stock air intake back on for this weekend hoping it would help. It only took about 20 minutes for the front of the carb to fill up with snow and slush. I am anxiously awaiting my smart carb. Has anybody had that problem with the pod filter? Will the stock intake help the icing issue? Thanks for the comments.
M
mtn-doo
Well-known member
No. It is not "snow" sucking through your pre filter. It is just carb ice. When moist air reduces pressure and accelerates, it dumps it's moisture on anything it can stick to. The humidity in the air is invisible but present everywhere. When the dew point is less than about 10 degrees from the air temp, it is close to saturation. When the air accelerates into your velocity stack, the pressure drops and the temp drops. The moisture then becomes a super cooled moist state and will stick to anything it comes in contact with. Pretty cool science. Like sublimation but in reverse. The 40 micron snow filter works fine. Snow dust will not hurt your engine nor will it stick to anything. It takes a combination of temp, dew-point to accumulate carb ice. Here is a great pic. Temp/dew-point spread of less than 7F and high velocity. Major ice. Pretty cool. Nothing to do with your filter. You can get carb ice without even being in a snow enviroment. I have seen carb ice like this pic I took on a clear day and no snow! Bare ground.
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todays hit
carb ice today, new 6" fluff but 30 degrees, not sticky, fast going down hill road leaving a riding area, engine building no heat high gear down hill, going 35 to 40 mph, KTM did WR didn't but slightly once, different gearing, different jetting, same carb different motors, you just never know on the icing.
carb ice today, new 6" fluff but 30 degrees, not sticky, fast going down hill road leaving a riding area, engine building no heat high gear down hill, going 35 to 40 mph, KTM did WR didn't but slightly once, different gearing, different jetting, same carb different motors, you just never know on the icing.
I haven't run into this yet, but I'm sure I will. Built an aluminum frame CR 500 with a timbersled on it. I have come up with two different ideas. One is to run a cooling line to the carb body and weld and aluminum tube to it, or wrap some copper tubing around it. The other is to attach the heating element off of a pet lizard rock onto the carburetor. This would require a lighting coil of course.
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portgrinder
Well-known member
Fine snow will get thru a pod filter. Had a day not too long ago where it did. And it was well before the carb. Scooped a whole handful out. Put a 2nd sock over that filter and it helped, but not eliminated.
I don't think that ktm heater element does much. No way to fight that much air cooling the carb as it goes thru with a small little element.
I don't think that ktm heater element does much. No way to fight that much air cooling the carb as it goes thru with a small little element.
Its not the fine snow that makes the carb ice. Just like MtnDoo said, the fine snow will not stick to the carb rather ingest into the carb intake. Its all about velocity and pressure and humidity !
In aviation we deal with it all the time in carbed applications ! You can be in clear skies and get carb ice. Plain and simple.
The KTM carb heat probably helps more than you think. It allows the intake temp to be raised just enough to prevent the supercooled condensed water from sticking to the venturi. Sure some conditions may overcome the heater, nothing is perfect.
Not sure if the Smarty can overcome the icing or not. It doesn't have bleeds to be covered by the ice. Also the fuel is proportional to what the engine requires signal wise. So whether the blockage is in the throat or on the intake it can compensate. Maybe APT can chime in and explain. Corey ?
In aviation we deal with it all the time in carbed applications ! You can be in clear skies and get carb ice. Plain and simple.
The KTM carb heat probably helps more than you think. It allows the intake temp to be raised just enough to prevent the supercooled condensed water from sticking to the venturi. Sure some conditions may overcome the heater, nothing is perfect.
Not sure if the Smarty can overcome the icing or not. It doesn't have bleeds to be covered by the ice. Also the fuel is proportional to what the engine requires signal wise. So whether the blockage is in the throat or on the intake it can compensate. Maybe APT can chime in and explain. Corey ?
Carb icing is a huge issue in general aviation planes. Ask any pilot, carb icing can happen at any temp.
All general aviation procedures require the pilot to apply carb heat before landing so in case of an aborted landing the motor can get fuel even if some carb ice is present.
Search YouTube for several videos the explane carb icing.
All general aviation procedures require the pilot to apply carb heat before landing so in case of an aborted landing the motor can get fuel even if some carb ice is present.
Search YouTube for several videos the explane carb icing.
I was battling carb freezing this weekend, first time it's happened in over a dozen rides. I have a carb heater on the way, I see the 2 stroke carbs have a spot to drill in the element, I am putting it on a 2010 KTM 450 sxf with a Keihin FCR, anyone have a picture of where they have installed the element on a 4 stroke?
I don't see anywhere on the intake side of my carb where there is enough meat to drill and tap the heater element, 4 stroke Keihin FCR. Any help would be great.
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portgrinder
Well-known member
Wrapped my carb in 5/16 line. Tee'd off my main coolant lines. One out of the head and one right before the water pump intake. Plumbed in a carb heat valve off the old doo XP setup.
Going to give it a try. Seems to circulate good and make some heat. Fits pretty nice under my carb jacket.
Going to give it a try. Seems to circulate good and make some heat. Fits pretty nice under my carb jacket.
M
mtn-doo
Well-known member
I believe M5 drilled and tapped the top hole on the first pic, parallel with the top of the intake. I looked at it in my shop, but not positive? He may see this and jump in...?
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portgrinder
Well-known member
Tested this out today. makes quite alot of heat. snow wasnt loose and it was warm so no issues, but i think theres no chance of any ice staying in my carb with the amt of heat i can put to it now.
Also i think running the smallest pilot jet possible will help. that will mean less turns out on your air screw vs running a larger pilot. so when the air screw opening is restricted with ice you are closer to the un-iced fuel mix.
ie a small pilot with the air screw almost closed will be way less effected then the air screw plugs than a large pilot with the air screw out quite a ways.
Any pictures of your setup?
Fighting Carb Ice
I'm running a 2013 KTM 300 XC-W with an APt Smartcarb. The issue for me is that my carb slide sticks wide open. Gets exciting in a hurry. So, I have attached a 75 watt heat pad (Overkill, I have ordered a 25 watt) to the side of my carb with high temp Silicone. I have also wrapped the carb in a Cordura sack I made and insulated it with Insulbrite. The heat pad is wired thru a relay and switch which I can cycle on and off. One other issue I have found is that moisture does collect in the air filter even with a pre filter. So I carry 2 extra filters and pre filters. It all boils down to Moisture Management.
I'm running a 2013 KTM 300 XC-W with an APt Smartcarb. The issue for me is that my carb slide sticks wide open. Gets exciting in a hurry. So, I have attached a 75 watt heat pad (Overkill, I have ordered a 25 watt) to the side of my carb with high temp Silicone. I have also wrapped the carb in a Cordura sack I made and insulated it with Insulbrite. The heat pad is wired thru a relay and switch which I can cycle on and off. One other issue I have found is that moisture does collect in the air filter even with a pre filter. So I carry 2 extra filters and pre filters. It all boils down to Moisture Management.
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portgrinder
Well-known member
Here's some pics.
Looks a little bit farmer style but I think it will work. Tons more heat than that ktm deal. And no electric power needed so you could run it if you don't have the amps, or a bigger headlight ect
The hose looks like junk but it's rated pretty good. -40 to +175c I think.
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portgrinder
Well-known member
just an FYI this works fantastic. makes lots of heat. can open the valve wide open if you need it or just crack it a small bit.
doesnt seem to change coolant temps at all. thought it might
followed 2 of my buddies on sleds down the mtn at pretty good speed. it was cold with that real fine snow dust. not one issue. previously the carb would last about 2 minutes of this until it clogged up. then you gotta take it out, clean out the air screw inlet, reassemble.
KTM carb heater is like a candle, this is like a propane torch. and you don't waste any electrons.
doesnt seem to change coolant temps at all. thought it might
followed 2 of my buddies on sleds down the mtn at pretty good speed. it was cold with that real fine snow dust. not one issue. previously the carb would last about 2 minutes of this until it clogged up. then you gotta take it out, clean out the air screw inlet, reassemble.
KTM carb heater is like a candle, this is like a propane torch. and you don't waste any electrons.
