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Discussion Starter · #1 ·
hello everyone,i was riding on a freeway at 4000rpm in 16 c. when one of the pistons started to act as if i was running out of fuel,i pulled over to the shoulder and kept going ,gearing down for maybe 2 min. In second gear i gave it a bit of gas and we;re back to normal.
Is this ICING? Can it happen to a warm engine?
thanks
 

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Think literally of a slide sticking and not fueling properly, you are not running out of fuel but the slide is not moving as the demand for fuel changes so you can jump from rich to lean and back in steps. we often see it in cold weather especially if it is a bit rainy.

Fcr's have been used to fix the issue as it does not effect them.
 

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Discussion Starter · #4 ·
It's a1992 900 ss.Heater kit? did not know of the need for one.until now.What is it? This means that it's a common thing,eh? thanks for your interest.
 

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No heater on those, late models of the carbs have a electric heater added to them. There are some ducati kits that used the oil from the oil cooler to heat the carb bowls , I saw one on ebay not long ago but I do not think I would add one unless it is a big problem. Yes any CV carb (and some manual slide carbs too) with the right weather conditions and air velocity you can create icing. In New England we would have a few customers run into this a year. The few times most see it, just does not justify the fix most of the time.

If you are in wet/cold conditions try and keep the slide from sitting for too long in one spot if it starts to act up. vary the throttle to allow the slide to be constantly moving a little so it does not have time to ice in place. Worse case hold it at a fixed rpm and throttle so any icing has a chance to stick the slide.
 

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I know this is not Ducati but --I have a 1937 BMW R12, most of these bikes had a single SUM carb mounted- the intake manifold attached to both heads then went backwards to meet behind the engine. This setup was on a few earlier bikes as well, To eliminate the carb from icing ( and this was an issue)-they used what the called heat risers --These attached in between the exhaust pipe & the head with a pass thru hole but there was a tube that attached at the top of the riser with a small hole that diverted some of the heated exhaust gasses thru the tube's back to the intake manifold where they connected on both sides of the carb. --just enough heat to keep the carb from icing
 

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This is really interesting - I noticed that on the SS particularly among other carbed bikes that I've had that the carbs gets pretty cold even in a relatively warm weather.
 

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This is really interesting - I noticed that on the SS particularly among other carbed bikes that I've had that the carbs gets pretty cold even in a relatively warm weather.
So - Carb icing is a SERIOUS concern for carb'ed small planes. In fact, it's on the decent check list to turn the carb de-ice on before starting a decent. As the air warms and becomes more moist it will certainly freeze - and the engine will quit. Hope one has a nice dead stick landing spot picked out. My workshop manual for the 900 SSSP suggested they were installed for euro bikes. The UK would definitely qualify! BTW: Turning on the carb heat drops power - one way one knows it's working on a plane...
 

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So - Carb icing is a SERIOUS concern for carb'ed small planes. In fact, it's on the decent check list to turn the carb de-ice on before starting a decent. As the air warms and becomes more moist it will certainly freeze - and the engine will quit. Hope one has a nice dead stick landing spot picked out. My workshop manual for the 900 SSSP suggested they were installed for euro bikes. The UK would definitely qualify! BTW: Turning on the carb heat drops power - one way one knows it's working on a plane...
I would love to see the info on the carb heating setup on Euro bikes, My 91 900SS was sold and lived in Italy--I see nothing anywhere around the carbs, engine etc to ever think that something was there for carb heating--Of course I may be missing something, But I'm in Florida so the issue of carb icing is not something that worries me at all lol
 

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Discussion Starter · #11 ·
ok,thanks ducvet,yesterday went for a ride at 15 c. along the freeway at 4000 rpm and doing maybe 100kms,and it started to miss.I then moved the throttle a little bit to make the slides move and that was it ,back to normal.
While here,may i ask if the pilot screw in our carbs is a fuel or air screw.thanks:giggle:
 

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It's actually not the slide that sticks but the opening of the needle jet which closes due to ice build-up. Gasoline is sucked into the ventury through this jet and causes locally a serious drop in temperature (gasoline going from liquid-->gas causes a drop in temperature). Same principle as a refridgerator. When pressure drops, temperature drops. And as with all liquids; going form liquid to gas requires heat (which is taken from the air and the jets).
If temperatures are low enough and humidity is high enough ice can build up on the ice-cold needle jet. Water vapour from the air freezes on the needle jet and clogs the opening.
 

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Worst icing that we have encountered on our 900’s is on my wife’s 1995 with stock carbs, in 15-18C temperatures, heavy rain, heavy traffic and lots of road spray/mist. It would shut right off. When you looked at the exterior of the carbs there was frost on them. Pull over and let the engine heat soak back up into the carbs, and be on your way again for a few more kms before the jets froze up again. We added a NOS carb heat kit (supplemental oil lines from the oil cooler to modified float bowls with oil passages in them to keep the carb bodies warm) and have not had a problem since. I have 41 FCR’s on my 1994 900 and have never had a problem with carb icing. The FCR’s are well worth the upgrade price. My wife does not want them on her bike though as she is a purist and wants her bike to remain stock.
 

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Here is the FAA chart on the probability of carb icing versus temperature and dew point. I live in an area that has very high relative humidity especially earlier in spring, and the damn things would ice up even at relatively high throttle cruising 75mph on the highway if it was 10-12C. And in rain or wet road conditions under 20C, it was so bad I could almost count down until it started losing power every time. Frost around the outside of the carbs as well. Around here that alone was almost worth the switch to FCRs
 

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Discussion Starter · #15 ·
Here is the FAA chart on the probability of carb icing versus temperature and dew point. I live in an area that has very high relative humidity especially earlier in spring, and the damn things would ice up even at relatively high throttle cruising 75mph on the highway if it was 10-12C. And in rain or wet road conditions under 20C, it was so bad I could almost count down until it started losing power every time. Frost around the outside of the carbs as well. Around here that alone was almost worth the switch to FCRs
 

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Discussion Starter · #16 ·
Hello again
Well it happened again.Moving the slides wasn't helping.it was just like running out of gas.So, i lifted the tank,and saw the KINK.When the tank is lowered it kinks the supply hose (soft,and routed wrong).A pull here and there and i got home without anymore trouble. Already done 200kms. Thanks for the help,very interesting about the icing
 

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Here is the FAA chart on the probability of carb icing versus temperature and dew point. I live in an area that has very high relative humidity especially earlier in spring, and the damn things would ice up even at relatively high throttle cruising 75mph on the highway if it was 10-12C. And in rain or wet road conditions under 20C, it was so bad I could almost count down until it started losing power every time. Frost around the outside of the carbs as well. Around here that alone was almost worth the switch to FCRs
Nice chart Lelebebbel. Clearly from the pilots world and sure shows why one needs to add carb heat when gliding down through a wide range of temps.I gave my Hayes manual away when I sold my 1995 SS SP but I certainly recall there was mention of European variants that had a carb heating solution "built in" for some markets. Especially relevant for the UK - not unlike BC.
 

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The carb heat setup for the mikunis looks like this. It reroutes oil from the oil cooler through the float bowls to pre heat the fuel a bit. You need to find the float bowls with those integrated oil pipes obviously.
 

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