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As I was perusing the service manual the other day (yes, I actually read service manuals just for fun) I noticed that the Australia variant appears to have a liquid heated or cooled carburetor. At least that is what the cooling system diagram seems to show. And I went and looked at my KLR and, sure enough, the water pump housing casting has the boss where the Australian model has the port for the hose to the carburetor. What I didn’t see was what the carburetor looks like to see where the water goes on the other end.

Tom, Paul, anyone familiar with this variant? Do you know if the intent was to more quickly heat a cold carburetor or to cool a hot carb to prevent vapor lock?

Just a curiosity...
 

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I have a Vulcan pumper carb that, IIRC, had a heater circuit on it. I disassembled it but still have the parts.

It may have been the Australian fuels were at one time contributing to icing and KHI installed a heater. That’s what happened with the Vulcans.

At least, that was the Vulcan story with the 1500s.
 
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Carb pre-heat (seen pics of the setup from Aussie members), I believe.......also not needed IMO; it gets cold in Canada too from time to time! ;-)

Dave
 

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Carb pre-heat (seen pics of the setup from Aussie members), I believe.......also not needed IMO; it gets cold in Canada too from time to time! ;-)

Dave
Its not "pre-heat' Dave. It would have to be an Electric heater to do that. ;)

The European 'C' model KLR's received the anti-icing carb heaters. High humidity & cool temps can cause carb icing and those people ride in ALL Weather.

Numerous road bikes, atv's & utv's use carb anti-icing systems. Both electric & coolant variants.


If Watt-man could have purchased the anti-ice thermostat housings in the USA, he would have!
But he would have still needed to find a supplier for the 195F thermostats!
 

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Discussion Starter #5
Its not "pre-heat' Dave. It would have to be an Electric heater to do that. ;)

The European 'C' model KLR's received the anti-icing carb heaters. High humidity & cool temps can cause carb icing and those people ride in ALL Weather.

Numerous road bikes, atv's & utv's use carb anti-icing systems. Both electric & coolant variants.


If Watt-man could have purchased the anti-ice thermostat housings in the USA, he would have!
But he would have still needed to find a supplier for the 195F thermostats!
Did this require a different carb with built in water passages? Or was it a shroud that went around the carb somehow?
 

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Find #92005-1350 fitting in this schematic. https://www.kawasakipartshouse.com/oemparts/a/kaw/500b2597f8700223e478f08d/carburetor

The plastic fitting is divided, up & in on one side and down & out on the other. Only takes a trickle of coolant to do the job.

Just to the Left of the pilot mixture screw Tower is a pocket in the carb body. May be visible with a mirror? A (added) tower on the float bowl is also drilled & tapped for the retainer bracket.
 

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...If Watt-man could have purchased the anti-ice thermostat housings in the USA, he would have!
But he would have still needed to find a supplier for the 195F thermostats!
Bill believes he needs a 3/8" bypass hose. That boss won't support anything that big unless (maybe) one were to bore it and press a pipe into it.

It would be slick, though.
 

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Discussion Starter #8
Bill believes he needs a 3/8" bypass hose. That boss won't support anything that big unless (maybe) one were to bore it and press a pipe into it.

It would be slick, though.
That was my thought when I saw that AU variant in the service manual. Seems like it would be a nice addition for the northern climes in north america. I suspect it would provide crisp throttle response a little sooner than otherwise.
 

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It may have been the Australian fuels were at one time contributing to icing and KHI installed a heater.
From my pilot training: There is a temperature drop in the carb when the fuel vaporizes. At certain humidity and temperature combinations this can lead to carb ice forming. This leads to a constricted intake and reduced power. The fix in airplanes is carb heat. Hot air from a shroud covering the exhaust (think old VW heater except that it works) is directed into the carb to melt the ice. Carb heat is pilot controlled and only used as necessary. Leaving it on full time also reduces available power because the charge density is reduced at elevated temperatures, i.e., cool air gives more power.

Fly safe,

jncdi
 

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Discussion Starter #10
From my pilot training: There is a temperature drop in the carb when the fuel vaporizes. At certain humidity and temperature combinations this can lead to carb ice forming. This leads to a constricted intake and reduced power. The fix in airplanes is carb heat. Hot air from a shroud covering the exhaust (think old VW heater except that it works) is directed into the carb to melt the ice. Carb heat is pilot controlled and only used as necessary. Leaving it on full time also reduces available power because the charge density is reduced at elevated temperatures, i.e., cool air gives more power.

Fly safe,

jncdi
Yes, I am quite familiar with carb icing (owned a VW Beetle that had the carb heat shroud hose removed and been a pilot since 1978). The curiousity for me was why was this only offered in Australia?
 

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Yes, I am quite familiar with carb icing (owned a VW Beetle that had the carb heat shroud hose removed and been a pilot since 1978). The curiousity for me was why was this only offered in Australia?
Heard tell; had something to do with Australian DOT regulations . . . can't reference, certify, or verify!

THINK I've seen an ATV carb or two with heating available; electric, and maybe water.

As the Cajun said in the boathouse regarding the water-heated intake manifolds of marine engine conversions, "That don't cold it, that hots it!" :)

The high humidity of marine operations contributed to carburetor icing, unless countermeasure were used (yes, even in Louisiana!). :)
 

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Since the general climate of Australia is so similar to the general climate of much of the US, I can only conclude that it might be a fuel issue. Their fuel may have characteristics that make it more prone to icing.

Either that, or it is another one of KHI's weird doings that defy explanation. It would not be the first or only one.
 
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I'd guess it was a regulation issue. ....whatever the reason, we don't need it and I can't see a good reason to add it unless you are one of the crazy people riding to Alaska in the winter or using your bike in freezing temps...and even then I'm skeptical. The last time we discussed this "elsewhere", I believe one guy claimed to have had an issue well below freezing once......I ride down to just above the freezing point and have never had a carb icing problem and I doubt I ever will. Yes, I'm aware of the physics and it's a real phenomenon and I understand that a freezing carb is a bit more of an issue at 20,000 ft (where it's also really, really cold).

2 cents,
Dave
 

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Since the general climate of Australia is so similar to the general climate of much of the US, I can only conclude that it might be a fuel issue. Their fuel may have characteristics that make it more prone to icing.

Either that, or it is another one of KHI's weird doings that defy explanation. It would not be the first or only one.
I'm going to pick the latter! :grin2:


Dave
 

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It doesn't have to be cold and wet to have carb icing. That said, I've ridden in conditions from 25*F to 115*F in dry, humid, rain, snow, sleet, and hail and never had an issue. In fact, I'd say we all have.

The funny thing is, the carb heater won't do any good until the coolant is hot. With no bypass on the stock KLR it can take several minutes to get that hot. If the conditions are right for it, carb heating happens instantly and will happen as soon as the engine starts. With carb icing the engine won't run, so the coolant won't get hot. Thus, the carb heater is only going to help with icing if it happens after the engine is warmed up. It's just weirder than green shit.

I go with number two as well.
 
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The first gen (carb model) R6 had a carb heat system, but only on the California model. My understanding was it had something to do with assisting in passing a certain portion of the CARB emission test without making other carburetion changes. One short bypass tube and 3 plugs and it became a 49 state model. Was a nightmare trying to work around all that tubing when doing anything.
 

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Yes, I am quite familiar with carb icing (owned a VW Beetle that had the carb heat shroud hose removed and been a pilot since 1978). The curiousity for me was why was this only offered in Australia?
I'll suggest that KHI never Offered the carb heat system in Australia, it was Required. The question is why?
Did KHI ever spend an unnecessary dollar on the lowly KLR? (Don't answer that!!)



It doesn't have to be cold and wet to have carb icing. That said, I've ridden in conditions from 25*F to 115*F in dry, humid, rain, snow, sleet, and hail and never had an issue. In fact, I'd say we all have.

The funny thing is, the carb heater won't do any good until the coolant is hot. With no bypass on the stock KLR it can take several minutes to get that hot. If the conditions are right for it, ( carb heating happens instantly )??? and will happen as soon as the engine starts. With carb icing the engine won't run, so the coolant won't get hot. Thus, the carb heater is only going to help with icing if it happens after the engine is warmed up. It's just weirder than green shit.

I go with number two as well.
Is that a typo in Bold, Tom??

Actually Tom, I will dis-agree about coolant temp and carb ice. 35 - 40F coolant should prevent the carb from icing during the final stage of initial warm-up.
(I've never thought to measure cylinder head thermostat pocket temp 15, 30, 45 seconds into warmup, have any of us?)

I've never seen carb icing happen immediately upon starting, soon after I have seen on air cooled ATV's in WY winters. (Let me suggest 5 minutes of full choke & starting to reduce choke. The exhaust note sounds like someone else is pulling the choke back on!)
A single wooden match can sometimes be the remedy.
 

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It is a typo, should have been "(carb icing happens instantly)"

This under the idea that if carb icing is going to happen it will happen before the engine has a chance to warm up enough above ambient to heat the carburetor and that it doesn't have to be cold and crappy for carb icing to occur. That idea comes not from experience (which you have and to which I defer) but from the physics of the phenomenon of vapor cooling/carb icing.
 

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This is an interesting article that frames the problem from a light aircraft perspective. This quote from the article:

"In reality, certain situations are considerably riskier than others. Icing is most likely to occur—and to be severe—when
temperatures fall roughly between 50 and 70 degrees F and the relative humidity is greater than 60 percent."


Since this problem is widely recognized, and experienced, in aircraft, I can't help but wonder what barometric pressure may have to do with it, though the article says (and this is not news) that:

"At a basic level, carburetor ice is a product of three interrelated factors:
1) Air temperature
2) Relative humidity
3) Carburetor design"


https://www.aopa.org/-/media/files/aopa/home/pilot-resources/asi/safety-briefs/sb09.pdf?la=en&hash=526443ED8798604D33A89490F116E9EE2C281F6C

This is an interesting topic, one that I'm glad we really don't see on motorcycles. At least, if we do see it we simply roll to a stop whereas in an aircraft you can quickly run out of airspeed, altitude, and ideas. ;^)
 

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Discussion Starter #20
I will have to change Tom’s statement a little before I can agree with it. Carb icing “starts” to happen instantly in the form of a thin layer of frost. However, it can take some time before the affects get pronounced. And it is important to keep this part of the article in mind also: “Carb ice can form over a wide range of outside air temperatures and relative humidities. While the word “icing” typically brings to mind blustery winds and frigid conditions, carb ice can form when outside temperatures are as high as 100 degrees Fahrenheit with 50 percent relative humidity. At the other end of the spectrum, the risk doesn’t go away until the humidity falls below roughly 25 percent and/or the outside air temperature drops well below freezing.”

I have flown light airplanes for more than 40 years and owned a C-182 for a number of years. I have only experienced carb ice a few times as standard procedure is to apply carb heat in conditions where icing is likely to occur - generally during times of low power operation such as practicing approach to landing stalls and in making actual approaches to land. So, the idea is to try to prevent carb icing with carb heat rather than correct it once it has occurred. The reason being that by the time you notice power loss from carb ice, you may have accumulated a fair bit of ice. And when you apply carb heat, ice does what ice is wont to do when warmed and turns to water. Dumping a slug of water and ice chunks into your engine can make life interesting when in an airplane.

The worst carb ice encounter I had was with a 1975 VW Beetle than had been converted from FI back to carburetion. Yes, early mechanical FI systems were actually less reliable than carburetors. Unfortunately, I bought the car used after the conversion had been done and I was young then and didn’t think to look the engine over closely. It turns out that whoever did the conversion didn’t quite complete the conversion and had failed to install the hose that goes from the exhaust cuff to the air cleaner snorkel and provides warm air to the carb in cold weather and light throttle.

I was attending college in Erie, PA which is about 200 miles west of where I live. The first year I was there, I was heading home for Christmas break in early December and a wicked cold spell came through the day I was to leave. I left after my last finals, probably around 5 PM and I had a rider with me who I was dropping off in Salamanca, NY, which is about 80 miles into the journey.

The Bug started to run a little roughly as I came into Salamanca and I thought it was just some ice in the fuel lines so I added a can of drygas and continued on. The temp had been probably in the upper teens or low 20s when I left Erie, but was steadily falling and was in single digits in Salamanca well away from the moderating effect of Lake Erie. The Bug continued to run rough and lose power on the hills, but would gradually get better as I climbed the hill and then get really bad going down the other side. This continued for the next 70 miles getting progressively worse until the car completely died as I was climbing the hill just after passing Hornell, NY. Trying to get someone to stop and pick me up after dark, at temps around 0, is a whole nother story. And not really being well dressed for such weather didn’t help, but I digress.

The next day my dad and I went back to retrieve the Beetle. The first thing we did was remove the air cleaner and found a ring of ice at least 6 mm thick all around the inside of the carburetor. It was still near zero so the only melting that would have occurred was from the engine heat as it cooled down, so I suspect there may have been even more ice at the time the car died.

So, I would not call 70 miles and probably an hour and a half to be “instant” carb icing. The icing tends to form fastest and have the greatest affect when at part throttle as you have the most venturi effect cooling and the ice interrupts the airflow most then. Often engines will run OK at full throttle with some ice only to die when you pull back the throttle. I was lucky in that at OATs near zero and the typical low humidity of winter, it took a long time for enough ice to form to kill the engine.
 
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