ChevyFazer
Redneck MacGyver
If that stuff was already on the bike then it's possible that it has been jetted for the extra air flow
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Fazer 600 carb icing ?
- Thread starter needlessfred
- Start date
The short answer to the original post is to apply some heat to the carbs.
OK - New lesson here. . .
Carbs can ice at nearly any outside temp. In fact it has less to do with the outdoor temp and more to do with the design and distance the carbs are from the combustion chamber (they loose the radiant and induction heat through the connecting materials). Its the flow of air through the carbs (carbs are restricting it) and then expanding again just after the throttle plates that makes the icing occur. So the question is why is this one different than others?
- break -
once the external icing is underway it causes the fuel to return from a vapor back to a solid which the engine has a hard time burning. Hint:> Think of me sticking your head under the water every 30seconds vs just breathing in the air at 90% humidity. its not going to go over well.
Because of the icing, (fuel dropping out of vapor suspension) its going to smell rich as combustion will not be complete. As of this moment, don't jump to the conclusion that its running too rich. That a symptom of its condition.
Also - under icing conditions any small amount of water in the fuel is now very much a solid and further cripples the engine as far fossil fuel burning is concerned. Its going to stumble and misfire, not accelerate well, cut out, blow black smoke ect.
So tell me about this bike; it has a coolant system and you say there is hot water going to the carbs. Any chance the hoses have been switched and what should be the hottest water from the engines head is now the colder water after being through the radiator??? This would be Big deal!!!!
Also tell us about how you ride. This icing thing is a bigger issue from throttle positions from 30 to 60% vrs 70 to 100% throttle.
Can someone find some pictures of this engine and carb setup? I'd love to know the general distance the bodies are from the head and how much of the coupling material is not aluminum. Hint - this problem is bigger the further the carbs get away from the engine as the venturi cooling effect is greater in long runners.
OK - I'm done blahbing. . . time to think for a minute.
OK - New lesson here. . .
Carbs can ice at nearly any outside temp. In fact it has less to do with the outdoor temp and more to do with the design and distance the carbs are from the combustion chamber (they loose the radiant and induction heat through the connecting materials). Its the flow of air through the carbs (carbs are restricting it) and then expanding again just after the throttle plates that makes the icing occur. So the question is why is this one different than others?
- break -
once the external icing is underway it causes the fuel to return from a vapor back to a solid which the engine has a hard time burning. Hint:> Think of me sticking your head under the water every 30seconds vs just breathing in the air at 90% humidity. its not going to go over well.
Because of the icing, (fuel dropping out of vapor suspension) its going to smell rich as combustion will not be complete. As of this moment, don't jump to the conclusion that its running too rich. That a symptom of its condition.
Also - under icing conditions any small amount of water in the fuel is now very much a solid and further cripples the engine as far fossil fuel burning is concerned. Its going to stumble and misfire, not accelerate well, cut out, blow black smoke ect.
So tell me about this bike; it has a coolant system and you say there is hot water going to the carbs. Any chance the hoses have been switched and what should be the hottest water from the engines head is now the colder water after being through the radiator??? This would be Big deal!!!!
Also tell us about how you ride. This icing thing is a bigger issue from throttle positions from 30 to 60% vrs 70 to 100% throttle.
Can someone find some pictures of this engine and carb setup? I'd love to know the general distance the bodies are from the head and how much of the coupling material is not aluminum. Hint - this problem is bigger the further the carbs get away from the engine as the venturi cooling effect is greater in long runners.
OK - I'm done blahbing. . . time to think for a minute.
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Good point on freezing! You wouldn't think that if you were to bring in air above freezing that it would not cause a carb to reduce it's temp below the freezing point and ice up. One lonely factor could easily create a below freezing throttle body, especially when you're only a few degrees away from the freezing point. That would be gas expansion. When we expand certain gasses that have much lower boiling points they act like a refrigerant would. Maybe not as efficient as say freon but non the less the area they expand in will drop in temperature.
Being that the the engine easily cold start with no choke and runs better cold as apposed to hot, I think he's got a rich mix and I don't think it's an icing problem.
Being that the the engine easily cold start with no choke and runs better cold as apposed to hot, I think he's got a rich mix and I don't think it's an icing problem.
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The fact the design even has hot water to the carbs makes me think its an issue they had to compensate for. Although I agree it could be from being too rich, I'm hesitent to say change the jets or needle distance. The fact that it starts cold easily almost suggests theres a leak allowing fuel to be where it shouldn't be all the time. So - if the hot water is not found to be the issue, I'd opt for CARB kits tear them down and inspect them and find the source of the unwanted fuel delivery.
lastly - I didn't state the obvious in plain english. Frozen carbs plus water in the fuel can shut an engine off very quickly although its likely to hit all four carbs at once...
needlessfred
Junior Member
OK
I think ive found the problem
It is carb icing . I traced the pipes that feed the hot engine coolent though the carbs and found that they are blocked . the coolent is flowing from the pump but not getting to the return that gos to the radiator
Im going to blow compressed air though the feed when i get to work and see if it will unblock the pipes .
The reason the spark plugs are black is that the carbs icing restricts the air flow messing with the fuel mix .
Thanks for all your inputs
I will post here if it works or it will have to be carbs off for a good clean...
I think ive found the problem
It is carb icing . I traced the pipes that feed the hot engine coolent though the carbs and found that they are blocked . the coolent is flowing from the pump but not getting to the return that gos to the radiator
Im going to blow compressed air though the feed when i get to work and see if it will unblock the pipes .
The reason the spark plugs are black is that the carbs icing restricts the air flow messing with the fuel mix .
Thanks for all your inputs
I will post here if it works or it will have to be carbs off for a good clean...
ChevyFazer
Redneck MacGyver
Probably wouldn't be a bad idea to flush the system as well, the best radiator flush I've ever used is cascade dish powder, i have never tried it on a bike but it has worked wonders on every other vehicle I've done it on. So far I haven't had the need to use it on a bike but something to consider.
needlessfred
Junior Member
Yeah that sounds like a good idea
Ive not changed the coolent since ive had the bike
That should stop the pipes getting blocked in the future
Thanks
Ive not changed the coolent since ive had the bike
That should stop the pipes getting blocked in the future
Thanks
red_rock_beetle
Junior Member
just a tip, if you ever do come across a misfire and you want to know what cylinder it is without having to pull the plugs, what i do is get out my infrared thermometer and check the exhaust a couple inches away from the head, it will be obvious which cylinder is not firing:thumbup:
just something i picked up tuning hopped up old VW motors in dune buggys and such
just something i picked up tuning hopped up old VW motors in dune buggys and such
just a tip, if you ever do come across a misfire and you want to know what cylinder it is without having to pull the plugs, what i do is get out my infrared thermometer and check the exhaust a couple inches away from the head, it will be obvious which cylinder is not firing:thumbup:
just something i picked up tuning hopped up old VW motors in dune buggys and such
Poor boy method is a squirt bottle. . . simply seeing which one evaporates the slowest but I/R therms are $25 these days. A good investment!
Glad this shed some light on it. Hopefully its easily cleaned and all is well. I would be tempted to use an old coat hanger vs high pressure on the carbs (no more than 30PSI????). If its rusty, could blow out and be nightmare.
Let us know what comes of it.
FP
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