Ducati Monster Forum

I periodically raise this issue, so thanks for your patience. ;D

With FCRs, the issue of carb freezing went away. Since my Monster is back to CV carbs and winter is approaching with a vengeance, I am considering my options in dealing with carb icing. Although our winters here aren't anything like those you northerners experience, our cold is humid, perfect for carb icing. I once saw ice on the outside of the inlet manifolds of a mate's bike; really. I couldn't believe it considering the manifolds are alloy. The ice melted once we were stopped and my buddies bike sat at idle for awhile.

I will test with exhaust heat insulating wrap around the inlet manifolds as a first option. I'm hoping that trapping heat in the inlet tract while keeping wind chill airflow off the outside of the manifolds will promote atomization and prevent icing along the inside walls of the manifolds. First giving the bike a good warm up is going to be important to promote heat saturation before the air velocity increases. The mod is simple and reversible come summer.

Like others I found the oem float bowl oil jacket kit a failure back in 1996-1997. Others again say the oem electrically heated bowls don't get hot enough. I like the electric float bowl heater idea better and would consider making my own if the "carb sock" doesn't work.

Anyone tried the carb sock idea? If you think it's futile, I'd like to know why.

Interesting idea using the insulation wrap.  Might actually keep the carbs a little warmer, if not, winter performance might still improve.  Blocking off the oil cooler might help a little too.  My guess is the reason for the oil heated cars not working was at least in part to not very hot oil.  My old 750 oil temp could be down around 60^oC on the highway.  Maybe with the other modifications the silly electric heaters might stand a chance.

Yeah, maybe fitting the electric heaters with carb socks could work in combination. I'd run a set with a manual switch if I fitted them. I reckon you could make a set with little elements and controller from the electrical hobby store. Or burn the bike down. [laugh]

If I decide to build my own electric warming kit I will definitely be seeking your advice.

I went through the search function tracking the discussion on this topic. Someone has gotta find a fix.

run a heating element (hairdryer etc) inside the airbox, before the fuel is involved? somehow add in a thermostat based in the manifolds, so you can run the element only when required, to get the air temp required. just a random idea, no idea if it's plausable!!

the socks sound so much simpler now  [laugh] [laugh]

maybe cut up a set of heated gloves??

Good on you blokes for thinking laterally.

For an electrical solution it's finding an element hot enough but not too hot, and small enough to fit in the float bowls.

I was thinking of utilizing the existing bolt holes in the float bowls that take the oil heater kit. I was hoping to shove an element of some sort in there and have a manual switch. The Shorai battery would warm up when it warms up the float bowls before hitting the starter, killing two birds with one stone. If the carb sock doesn't work, heating the bowls is the next thing to try. As Howie said, it may take a couple of things to work together. I'll ask the Ducati or Triumph dealer about the parts they use for these kits.

Are there any electrical fuel warmers that run in line? That would be a plug and play solution. Or are there additives to put in the tank with each fill up? Couldn't find any here last time I looked.

Certainly easier to use the engine's own heat to do the job by trapping it.

Arctic Fox make diesel fuel heaters designed for rigs in Alaska and Arctic Europe. A bit hot for gasoline! :o They even have a fuel line with a built in element in sizes down to 2". A unit for gasoline/petrol would be plug and play.

Notes from PILOT FRIEND Website: Fixed Wing Flight Training re Carburettor Icing.

I guess it's pretty important to these guys :o.
Forum flyboys (and girls) feel free to comment.

Three types of carb icing.
1. Impact Ice: Ice forming on intakes and air filters from snow, rain and sleet between 15-32F. Unlikely.
2. Fuel ice : Vaporized fuel freezing on entry into the manifolds. Likely at 50%+ humidity and temps between 40-80 F. Most likely for us.
3. Throttle Ice : Ice on throttle butterfly, venturi and slide from freezing water vapour at between 32-37F. Possible.

Looking at No.2, trapping heat in the manifolds might be promising. A fuel warming system that actually works has potential.

More useless info for you guys in the tropics.

Looking at the parts diagram, the electric heater has elements entering the side of the carb body on the 2001 M750. It's an attempt to warm the carb body itself to stop icing. That's a lot of metal to heat with the low watt element. The oil system of the earlier models warms the float bowls to warm up the fuel, but if the oil is warm enough to warm the fuel in the bowls then it was probably warm enough weather to not need them.
I think electric heating of the float bowls themselves is the answer like Triumph do on their carb models.

i dont know if this would be of any help. this one seems to heat the carbs off the oil.

http://www.ebay.com/itm/1991-1998-Ducati-750SS-900SS-cold-weather-carburetor-heating-kit-69920371A-/360874129096?hash=item5405c636c8 (http://www.ebay.com/itm/1991-1998-Ducati-750SS-900SS-cold-weather-carburetor-heating-kit-69920371A-/360874129096?hash=item5405c636c8)

Thanks DL.
That's the old oil heating kit that didn't really work. My first Monster had one fitted under warranty and it made no difference until the weather was warm enough to not need it. Seems the oil temp is kept down quite well on these motors in winter.

Did you ever try blocking off the oil cooler when it was cold?

Iirc the kit on my bike had a tap that redirected the oil from the cooler to the float bowls and back to the oil system. It made for very messy plumbing. It bypassed the cooler via a simple on/off tap. I had a vinyl cover on my Shovelhead's Lockhart oil cooler and I reckon that made a difference on that bike.

Yeah makes sense after you mentioned it. Even takes my fuelly ss awhile to get up to operating temp on a 60 degree day.

I don't think the heated oil set up is a bad idea...if the oil gets hot. The oil doesn't on a bike with a cooler on a 40 degree day.

You'd reckon it should get bloody hot quick enough to do the job ay? A cooler cover is an option; it certainly made a difference on my Shovel. The oil lines to the carbs are a mess though and really get in the way when servicing the carbs. I'd sooner wrap the manifolds or have the less messy plumbing of a couple of wires to the bowls.
Me mates ZX9R had coolant heating the float bowls and his bike froze its Keihin CV carbs more than my Mikunis ever did. I'm guessing the problem is further up the intake tract, and that's making me want to try the manifold wraps.
Only one way to find out, and we sure have the weather for it. :P

The water temp on the ZX9 get up to normal on a cold day?

I don't think you can get an electric element with enough power to do the job on the volume of air required.

An electric element with inso might work on the float bowls, but it still will be a PITA to service.

I reckon the thermostat barely opened. I thought the coolant would warm up quicker than oil, but not reach as high a temp when warmed up. Amazing how the CV slides cause the issue. Strange thing is the Kwaka had short, rubber manifolds unlike the long alloy ones on the Harley and Ducati.

Tested the bike on this cold morning with no exhaust wrap on the manifolds. Although the bike took awhile to warm up, it did not have any freezing issues. A factor in this could be the stock airbox . I note that the last two bikes with open airboxes had a great deal of problems with carb freezing, much worse than this bike and a 900SS also with closed airboxes. Also, the one bike with ported inlet manifolds, all things being equal, also had less carb freezing than the others. Not a big sample, (only four bikes), but noteworthy.

Anyone experience this, or did you find no difference?

The only time I experienced icing the bike still had a closed air box.  It does make sense that a closed air box would help since the air might  have a nano second or so to warm up.

I doubt there's a market for it, but it seems like someone could make a float bowl with a pass-thru to put a small heat element in and heat the bowl. 

Wouldn't need to be much -- just enough to keep it above freezing -- but IIRC gasoline freezes at about minus 40F..  where the hell do you live again?

Just like with fuel tanks the problem seems to be more with the associated water in both the fuel and atmosphere rather than the fuel itself.

Pretty sure water freezes at the same temp regardless where you live. ;D

More an atmospheric problem.  40 ish^oF, high humidity air.  Carb venturi effect.  Temperature drops.  Humidity in air freezes.  Colder, no moisture in the air to freeze. In conventional carbs the throttle plate wants to freeze open.  Our Mikuni carbs, the needle freezes.  FCRs rattle enough to keep ice from forming.

That would be untrue!  It depends on altitude (pressure) too, just like the boiling of water.. :-)

http://www1.lsbu.ac.uk/water/water_phase_diagram.html (http://www1.lsbu.ac.uk/water/water_phase_diagram.html)



Why don't the add-on CV carb heaters work? 

Case of should work in theory but not in execution. Also possibly other factors messing with the plan. My theory is that the long manifilds have such a ram air effect as to freeze down their length. Others have suggested this to me over the years so I thiught I'd wrap them and try and solve the problem "downstream", so to speak.

Electric method lacks oomph to heat the carb body and oil method doesnt get hot enough to heat the fuel in the bowls. Former puts element into the carb body and latter warms the bowls with an oil jacket.

Those methods dont give enough heat so I thought engine heat from the heads transferred to the manifolds and trapped there could be the answer. Maybe. My view being that upstream solutions have failed.

It doesnt get too cold down here by world standards but we have pretty humid cold as DP and Howie have described.

Never seen this issue with any slide carb be it Amal, Mikuni or Keihin. Never an issue with a straight butterfly carb be it Bendix, Keihin or S&S, but only CV carbs on a range of bikes including Hondas, Kawasakis, Harleys and Ducatis, both liquid and air cooled.

Warm the manifolds?

If you think about it...

it makes sense because the CV slide has no return spring. It relies totally on vacuum.

Yep, by trapping heat with exhaust wrap. I'm gonna give it a try.
Absolutely.
It's design modulating air velocity in front of the butterfly or slide rather than via a butterfly or slide is the issue imo. The two air metering devices, one after the other is what complicates things. So there's a lot more going on than just a mechanical part getting frozen stuck, but the air velocity issues (by design) which cause it. I don't have the book learning to explain it properly, but the CV concept of keeping air velocity high independent of throttle position is the culprit in my unlearned opinion. ;D

I think you have it right on why the needles freeze on the Mikunis Tony.  As I remember, freezing on Monsters was a big problem in England, first came the oil heat kits, then came the factory electric bowl heaters.  My memory is questionable though.  All carburetors are subject to freezing.  Common on cars was running either exhaust gas or coolant under the carb to help with both freezing and atomization of fuel when cold.  Later, more for emissions, came the thermostatic air cleaner too.  You are probably correct about the long manofoplds since they create a higher velocity at cruising speed. 

I'm feeling even more confident about the manifold wrap/carb sock option actually working after taking the Monster out for a run tonite. It was cold and misty with a frosty feel to the air around these parts and a little carb freezing occurred. 

Went for a good 30-40 minute ride and when I returned home I could hold the manifolds even though the motor was quite hot. The manifolds were quite cool for 3/4 of their length and only a little warm near the heads, but when I touched them again after 5 minutes of the bike sitting I could barley touch them they were so hot. I had forgotten about the heat saturation that works its way into the manifolds once the bike is parked.

The wraps should protect the manifolds from the external cooling effects of wind chill and allow internal heat saturation to occur from engine heat. If the manifolds could be that hot while the bike is running then surely that is a hell of a lot hotter than the oem oil jacket and wimpy electric element solutions. The best source of heat available for the inlet tract is from the heads.

I understand what you're trying to accomplish, but I'm having some difficulty understanding how insulation alone will counter the venturi effects of the volume of air in the manifolds and allow heat from the heads to soak into the manifolds while it's running.

The objective is any icing upstream will disappear downstream if its hot enough there in the manifolds. Theres nothing to do about the venturi effect bar changing carbs or using short manifolds I guess. Im just hoping to add heat. It will be more heat than the other methods.

I think oil is the best way to heat things.  What about putting a very small oil cooler between the manifolds? 

They make some very tiny coolers for go cart racing..

I wasnt very clear. The test was with no wraps and showed how much lost heat is available if the manifolds arent cooled by the wind. They got very hot once the bike was off and parked. My aim is to have the manifolds no longer subject to the air cooling and hot enough to be a counter measure to the venturi effect.

That makes sense since you would be drawing heat from the head and if they are covered will prevent air from pulling the heat off...  Interesting.

I'd be more convinced with a running but not moving test...like on a dyno.

I'll try with the wraps when they arrive and check the manifold temp after a ride. You reckon the internal cooling of the venturi effect will be too much for the heat from the head to work? Much of this solution comes from the manifolds being aluminium which also contributes the problem. The heat really transferred down the manifolds so I'm hopeful.



G'day Tiz
Anything to do with oil plumbing was my last option after the factory oil heater. You mean aim the little cooler at the bowls? I reckon any oil based solution would need the OEM oil cooler covered over, since it works so well.
Yeah, I want to keep the heat there and not let it dissipate. The alloy manifolds just transfer heat very well so I gotta turn it to our advantage.

I'm not sure Tony. Undoubtedly removing the effect from the outside cooling will help slow down the heat loss in the manifold. I'm just not sure enough heat will be retained to keep the needle from freezing.

I'm really hoping it will, I'm just having a hard time wrapping my head around it because I can't fathom the numbers.

Nate, it's all uneducated guesswork over here. ;D
I doubt the heat will do much that far up the inlet tract, but I think manifold freezing is more the problem on this model bike. I have seen a coating of ice on the outside of manifolds. Amazing.
I reckon bikes with ram air like the ZXR 900 get freezing at the carb bell mouth and needle, etc. The M900 gets all the air velocity down the long manifolds. Again I'm guessin' ;)

i think you could get creating with (say) copper piping.  maybe wrap the manifolds in it, multiple coils around using 5mm ID copper piping and then use the oil heaters for the carbs as well -- run the oil thru the coils and then thru the carbs heaters. 

does that make sense?  You'd use the factory carb heaters (oil) but would plumb them off a custom copper coil you fabricated around the manifolds.

cluster-F no doubt..

I understand. Might work too, but what a mess [laugh]

I'm gonna try $40 exhaust wrap first and some wire/cable ties. ;D

Maybe some of this stuff under the wrap?

http://www.heatingelementsplus.com/12-24-volt-self-regulating-cable-c-1_272.html (http://www.heatingelementsplus.com/12-24-volt-self-regulating-cable-c-1_272.html)

Thanks Howie.

That stuff might also let me make a float bowl or carb body heater. The recessed holes for the elements and banjo fittings might allow a place for hose to be fitted in either the bowls or carb bodies. What do you think?

Nate. Just did a simple "test".

I ran the bike at idle from cold in the shed and monitored the manifold temp. Gave the bike 5 minutes running at idle and fast idle, and the manifolds became hot except for the top 3/4 of an inch. The area is at the first bend just before the carbs and the longer radius side was closer to an inch of cold material, the shorter inner radius more like 1/2 an inch. That would be where the cold charge was hitting the radius. The manifolds became hot as the heat worked its way up their length over time. Of course as soon as I turned the motor off the whole length of the manifolds became too hot to touch very quickly, including the spigot rubber's retaining clamps.
It certainly demonstrates the force of the venturi effect.

I remember years ago that stopping and letting the bike idle awhile defrosted the inlet tract. I would ride off and the bike would run fine for a few miles until it would start freezing again. The more I think about it the more I keep coming back to using the existing heat source rather than adding one.

A fast idle would sort of simulate a cruise scenario...at about half speed.

It might work. Like you say for the $40 bucks it's worth a try.

Here's a good idea.. trap the heat with a "controlled air flow"
(http://www.motorcyclespecs.co.za/Gallery/Ducati%20906%20Paso%20%203.jpg)

 ;D

Like you said, trial and error.  Maybe temporarily mounting some sort of temperature sensor  to make sure you don't over do it.

Rapped the manifolds with carbon coloured wrap from where they bolt to the head right up to over the spigot rubbers up against the carb bodies.
Will ride to work today with the temps ranging from 5-13C out here with high humidity plus added wind chill factor. Should be good for icing. ;D
I'll give the bike a good 5 minute warm up and see how she goes.

First impressions.
The ride home tonight was very cold and I could feel the bike running well, better than it could have. It seems as if the wraps have helped to a degree but that more severe conditions could pose problems. Ill keep riding the bike over the winter to find out.

The float bowls were cool to cold to the touch but not very cold. Surprisingly, the throttle shaft caps were tepid to lightly warm to the touch. The insulating properties of the wrap appear excellent, you can hold the manifolds at idle and feel no heat coming through. Maybe some heat is working its way up there.
Nibor is lending me a  temp tester for real data.

Rode the bike all day today. It was bloody cold this morning with up to 87% relative humidity. I could feel the bike trying to ice up at times, but once warm it was fine. The odd falter but no stalling kind of thing. It occurred when rolling off and the CV effect was high, there would be a pause when rolling back on, but that's all.

That about wraps it up. A good warm up is important to have any effect, and no doubt in extreme conditions the wraps only help a little. There's just too many ways for ice to form in the intake system and the wraps only help with one of them. I think they will mitigate carb icing, but not eliminate it. Oh well, it's something I 'spose.

Did you also block the oil cooler?

I didnt even think of it, just the manifold wrap. Good idea, no reason I couldnt wrap the cooler.

If your bike has cylinders with an oil jacket it will help retain heat even more. My '96 will still have condensation in the oil after a long ride at 40F ambient.

I've used duct tape, but had some adhesive transfer. You need something you can pull off if the day suddenly warms up.

It's an effective system alright. The Paris/Dakar bikes proved that.

 I'll rig something up and try it. I see  wrap and cable ties. ;D

On the old bike I used Naugahyde held in place with wire ties I could easily cut on an unusually warm day.  Helped a bit.  The new old bike has an oil cooler guard that should make the task easier.  Shame Ducati doesn't run a thermostat for the cooler.

There was an aftermarket one available from the same guys that made the slave pistons...Evoluzione I believe. Eric didn't like them because they reduced flow even when fully open.

Had a cover that velcroed onto my Harely oil cooler. My upholsterer could make a nice one lined with exhaust wrap. Hmmm.

Not sure it needs to be that involved. Just needs to stop air from flowing through.

Yes, I remember that.  Didn't know about the reduced flow. 

I had some naugahyde which I cable tied on over the oil cooler. I added a tiny pair of side cutters and spare ties to the tool kit. Nothing melted and the bike warmed up quickly.

The bike ran the smoothest ever with CV carbs in cold weather that I can remember. I rode over the local mountain on this misty late afternoon (a good test) without any hesitation or rough carburation. Just letting a bike warm up as you should really helped. I still doubt the CV carbs will get through unscathed in extreme conditions, but this was another incremental improvement. I feel motivated to do the Full Monty on a spare set of CV carbs as a future project.

Thanks you blokes.

Clearly the time of the previous post proves I finally got it right :o.

11.11.11pm.

Final update and we can close the book on this one.

Recently did over 100 miles through the local mountain ranges with no significant carb icing, but for a very occasional slight roughness at part throttle. There was plenty of elevation, damp, mist and bloody cold, on the kind of roads that had grown lichen/moss. A pretty good test.

I never got around to borrowing Nibor's spot temp tester, but the riding tests showed that at temps down to 5-10 C the carbs would function fine with wrapped manifolds, the oil cooler covered and a warm up. Letting the motor run warmer and then trapping that heat in the inlet tract appeared to work quite well.

My riding buddy was on a Triumph America cruiser with electric float bowl heaters and it did not miss a beat. He had no idea that carb icing existed, so the system Triumph uses appears to work. I checked the Triumph's float bowls and they were not chilled like the Ducati's, just a little cool, so appreciably "warmer".

I can let this thread go knowing that I have a reasonable if not excellent solution.

Nice to hear your bowls are warm. 

Made bugger all difference to the bowls, but got the manifolds nice and hot.
Not a perfect solution, but it'll do.

have to say it just right.

 [laugh] [laugh]

Just an update.
I have been riding the Monster alot in this early cold winter and really enjoying it despite having detuned the motor by about 6hp and softening the response. I can confirm that if I dont give the bike a good warm up before riding there is evidence of carb icing until the motor warms up. If I let the motor warm up, the basic steps taken result in no carb icing and me riding in weather I previously would not have considered.
It seems to work down here with our mild southern winters.

Warm bowls dont help if you have a frozen tract ;).

 ;D

Sounds best with a Southern drawl. ;D

Down 'round Melbourne?   [evil]

I was thinking about htis issue before and I think wrapping the manifolds is about as good as you're going to get without some external heating. 

Borrow some heat from the head.  Maybe wrap in exhaust wrap and them a little velcro'ed jacket

Yeah, seems to be working. [thumbsup]