Carb icing.

[utopia]

Well, its that time of year again.
My 750 had an early morning splutter in the cold and damp last weekend.

My bike has the electric carb heaters, but they seem to be virtually useless.
I have in the past tested both the heating elements themselves and also the temp sensor which controls whether they're active or not .. and all seemed to be well.
My single cyl Dommie also has an electric heater element in the carb.
I can't recall it ever icing in the 15yrs or so that I've owned it .. and its done plenty of winter commuting in all conditions.
I am currently giving it a naked makeover and as part of that I have had all of the electrics off it and reworked the loom.
Therefore I have seen/found every component in the electrical system and ....
There appears to be no temp sensor for the carb heater element.
I'm assuming that it runs continuously (I'll check this when its rebuilt but it seems a reasonable assumption to make).
So I'm now wondering if the Monster needs its temp sensor at all, or whether it might be better to run the heater elements continuously.
After all, it isn't really temperature alone which causes icing, but rather the presence of dampness in the air in combination with low temps, so a temp sensor is not the most appropriate method of control.
Ok, we all know that a cooler charge is more dense and therefore makes a bigger bang, but does localised heating around the jet area affect this to any significant extent ?
I dunno, but the Dommie runs fine with constant carb heating .. and if I remember correctly its element is of a higher temp rating too.

Anyway, I'm toying with disconnecting the temp sensor on the Monster and seeing how things work out.
Although before I do, I might just see if I can install some sort of indicator light to tell me whether or not the elements are active at any given time.

I don't know if I ride my monster more than the average owner in the winter but I do seem to suffer to a greater degree with carb icing than others seem to report.
I guess this could suggest that the earlier, oil-fed carb heaters were more efficient than my electric ones .. though I'm not at all convinced by that.
My 750 does seem particularly prone though.
I suppose it could be that my particular fuelling set-up , or the particular characteristics of the 750 motor just happen to hit the rough spot, as it were.
Its all bog std, apart from hi-level, unbaffled termis which it has had for 23 of its 25k miles. No fuelling changes to suit the exhaust (yeah, lazy I know, but it runs well).

All this should become irrelevant by next winter as I have a pair of FCR39s waiting to go on .. when I eventually get round to it.
I'm still curious though.

And anyway, its always worth a timely mention of the dreaded carb icing at this time of the year, cos there's bound to be a new owner of a carby monster out there somewhere who will think their engine is on the blink .. as did I in my first year.
For that person I say, use premium fuels, preferably from BP or Esso, for a lower ethanol content.
Bung some proFST (Silkolene, I believe) in the tank .. about a teacupful seems to work for me.
Shut off early at the roundabout at the end of the bypass .. constant throttle encourages the icing and the throttle may not shut instantly .. but it will so don't panic.

[Mr Gazza]

I used to suffer from carb icing on my previous M900, and as you say it is not necessarily to do with freezing temperatures, but rather high humidity and lowish temps.
I found that the oil fed carb warmers worked well, but only when they were turned on of course! It's not always obvious when is an appropriate time to use them. (the tap was manual). I don't see that there would be any harm in running oil fed warmers all the time when the air temp drops below 10 degrees.
I now realise that I could have made them even more effective by raising the oil temp with a muff on the oil cooler.

Getting back to your electric warmers; it seems to me that they would be coming on inappropriately if they are temperature sensor controlled, unless the sensor is right in the venturi or in the tract immediately after it.
A humidistat would be better, but would probably need to work in conjunction with a thermal sensor. Surely much easier to rig a manual switch, perhaps also with an indicator light to remind you not to have them on needlessly in the Summer.

I bet you would find that they do work if they are switched on, like my oil ones did.

Taking a swerve for a moment... I had an Ajay twin that iced it's carb. I always knew it had done it because the bell mouth would fall off. Those twins needed a Paxolin or Bakerlite gasket between carb and manifold to prevent the opposite problem, which is fuel boiling or (unwanted) vaporizing.
Thinking about how heat is conducted and radiated through metal leads me to observe that the inlet manifolds on carb Ducatis are rather long and also made of aluminium. Exposed as they are to the cold air stream, both inside and out, they are going to get pretty cold and wonder if this is adding to the problem?
Maybe some lagging round the tracts might help?
Taking this idea further I thought maybe the lagging could include a heating element much like (or from donor) electric gloves?
I am picturing something that just velco wraps on and plugs into a conveniently placed connector.
Over thinking it, naturally, but I reckon a manual switch on what you have would be the way forward.

[utopia]

Yes I think you're right in saying that a temperature based switching for the electric heaters is inappropriate.
This was my thinking too.
And the clincher is that the temp sensor is mounted up near the speedo and idiot light cluster.
Furthermore, your suggestion of fitting a manual switch rather than my original notion of simply hardwiring the heaters to be continuously on makes a lot of sense.
Its funny how sometimes you can have all the info available but still not see the bigger picture.
I am now of the opinion that the best sensor for whether or not the heaters need to be switched on is ......me !!
..via the manual switch.
After all, it becomes plainly obvious as soon as the icing begins to happen .. and anyway I've developed a strong sixth sense about when its going to happen now.
Really, there is no better sensor than that as it reacts directly to the actual symptoms when they occur (or on the second occasion at least).
Just out of interest, I'm still a little curious as to how well the std temp sensor controls the system though, so I might fit an indicator light as well and then simply leave the manual switch in the "on" position all the time and see when the indicator lights up.
It should be a simple matter to remove the std temp sensor from the system at a later date to convert to a full manual system.
Its probably a fair bet that Ducati themselves would agree with the idea of a manual system being more effective (the oil-fed one is, after all) but the external control makes the system foolproof for all potential customers and maybe minimises any negative feedback (didn't work though, but you can see the logic).
And all this will be (famous last words ...."should" be) easy to sort out because the wiring is all up in the speedo region and my idiot light cluster has at least one, maybe two unused lights which I could use for the indicator.
Hmmm .. this might happen sooner than I was thinking.

[Mr Gazza]

, so I might fit an indicator light as well and then simply leave the manual switch in the "on" position all the time and see when the indicator lights up.


Surely you need to have a manual override of the automatic system, so you can switch the heaters on when the evidence shows carb icing but no light/heaters on?

So your manual switch would turn on the heaters and repeater light independently of the sensor. (I think you would need to wire the manual and automatic switches in parallel?)

[utopia]

Yes, you're right.
tbh I hadn't bothered pursuing the logic that far, but that's where I would have ended up anyway, I guess.

Another approach would be simply to make up a short wire link with suitable connectors which could substitute for the sensor .. and carry that in my pocket or lashed on the handlebars with a cable tie.
Then next time I'm out and the carbs start icing I can swap the sensor for the straight thjough link and see if there's any improvement.
Only downside with that is that my fingers are likely to be cold and numb at the time.
Also, the switch would make it easier to assess the effect of continuous heating on summer performance ... but I could just disconnect the link.
Maybe I don't really need the indicator light after all.
In which case the mod should be a piece of cake to arrange.
I'll nip and have a blimp at the connectors on the sensor.
I might even re-site it somewhere more convenient.

[Flip]

I now realise that I could have made them even more effective by raising the oil temp with a muff on the oil cooler.

So Mr G, are you seriously saying that the temperature of lubricating fluid can be raised significantly simply by putting the muff on the oil cooler of a Monster?

Should anything else be tweaked while this is done or is it just a case of getting the old bike hot before going for a ride?

[Mr Gazza]

Yep! That's exactly what I'm saying.
I have done tests with a temperature gauge fitted in the oil filler, gifted to me by Kato.

I found that it takes at least 10 miles for my Monster to even reach 50 degrees in cool weather (say below 10C) and that it hardly ever reaches 60C in those conditions.
Fitting a muff on the oil cooler, (gifted to me by Drumnagorrach) meant that she will rise to 60 reasonably quickly and maintain a healthier temperature throughout.

An oil cooler muff certainly does work. It has been proven that a Monster "over cools" in the normal British climate, and the Muff restores this during the cooler months.

I've never actually been one to warm up an engine when static, I prefer to set off gently after about a minute or less. I do live at the top of a hill though, so I can pretty much coast the first few hundred yards before putting any stress on the engine.
I always feel the engine will warm more evenly on the move?
Warming it up static will only warm up the heads?

[Flip]

Sorry I should have added some (in)appropriate smileys in my post- I couldn't resist it though- 'muff' is such an underused word these days!!

[Mr Gazza]

Oops! I completely missed that one didn't I?... Shoom!! :chuckle:

[utopia]

... 'muff' is such an underused word these days!!

Ah but Gazza is positively Dickensian.
Have you not seen his whiskers ?

Actually, Gazza, I don't recall seeing a closeup pic of your .....er, no .. well. :look:
What I was wondering is whether it was crochet'd.
And is it made in heat resistant material ? :eyepopping:
The reason I ask is that I have a friend who is trying to make a bit of extra money through her crochet.ing skills and I'm wondering whether to commission her to make me one.
There must be a kevlar/dacron/whatever modern thread that would fit the bill.
Mind you knowing her, I'm likely to get a couple of coloured daisies in the design.
I guess I could tolerate that at a pinch, if they were in blue/silver/gold.
Or maybe I could get her to adapt it into the circle/slash Ducati logo. :idea:

[Mr Gazza]

A picture of my muff you say?... I'll see what I can do.

[Mr Gazza]

There you go... Some pictures of my muff, including a full frontal.

It is made from woven glass cloth of some kind (not the type for laying up with resin.)
Nicely stitched in a double layer by Mrs Drumnagorrach. It has velcro at each end, so it can be wrapped round the cooler and attached.
I found out this evening that it is reversible, so I can have the clean side out this year.
It might turn out to be washable. I suspect I just fitted it till April though.!

Just thinking that the oil will rarely exceed the temperature of a tea pot, and so non melty fabrics might not be necessary (as in a tea cosy for instance).
Wool would be suitable, but for the wetting aspect (Wash-in water proofer?)

Drum' got his material from some sort of boiler insulation, I believe he is a heating engineer? Maybe one of those glass cloth, plumbers soldering, heat shield thingies would be suitable? Grumpy would know what they are called and where to get them.
(Edit... It's fire blanket aint it?)

https://s1.postimg.org/6r8ndhkqvj/Muff_1.jpg (https://postimages.org/)

https://s1.postimg.org/9u6tl826fj/muff_2.jpg (https://postimages.org/)

https://s1.postimg.org/1kto8zr1i7/muff_3.jpg (https://postimages.org/)

[Darren69]

When I was running my SS's and commuting all year round, I made a carbon sheet drilled with holes to cover the oil cooler (in an attempt to raise the oil temp) and also zip tied a solild carbon plate across the frame in front of the inlet tubes to deflect the cold air. Both helped but did not solve the problem completely even with Pro FST added, and even with the later modified float bowls with the oil lines fitted it would still ice around the same time everyday. Fag break time and it would be ok then for the rest of the jpurney. The flat slide carb conversion should fix it but I got so fed up I switched to an injection 4V which was the cheaper option.

[Dukedesmo]

I might fit an indicator light as well and then simply leave the manual switch in the "on" position all the time and see when the indicator lights up.
It should be a simple matter to remove the std temp sensor from the system at a later date to convert to a full manual system.


If you use a double-pole changeover switch you could have it 'on' or 'auto' (auto being on with sensor, as per standard) but if you got the same switch with 3-positions (the middle being off), you would have 'on', 'off' and 'auto' - essentially covering all options...

[Dukedesmo]

There you go... Some pictures of my muff, including a full frontal.


Was actually dreading the pics, thinking they might be merkin shots! :eek:



https://s1.postimg.org/6r8ndhkqvj/Muff_1.jpg (https://postimages.org/)



Nice Norton picture though... :thumbsup: