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D O G |
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D O G World Chat Champion
Joined: 18 Dec 2006 Karma :
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Posted: 12:53 - 16 Nov 2007 Post subject: Carb icing? How to fix? |
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Reet, need a bit opf advice and assistence from you fine folk...
I think the bike is suffering carb icing, symptoms are that when the air is cold (like this morning), it runs very poorly at low ish revs - like only on two or three cylinders.
I need to rev it loads to stop the misfiring, but it is only a temporary 'fix'. It has happened several times in the past on long, cold motorway runs - where the bike would misfiure and bog down briefly when I wind on a bit more throttle.
This morning, however was so bad that it was cutting out (revs would just die off) if I wasn't on the throttle and above arounf 5k revs.
It was a bit of a pain filtering down a hill, with the clutch in, half throttle to keep the revs up, and keeping speed down with the rear brake
Questions are;
1. Does this sound like carb icing?
2. What is carb icing?
3. How doe I fix it? (Strip and clean carbs was my thought?)
Thanks in advance! |
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Dalemac |
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Dalemac World Chat Champion
Joined: 15 Oct 2006 Karma :
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Kickstart |
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Kickstart The Oracle
Joined: 04 Feb 2002 Karma :
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Posted: 13:10 - 16 Nov 2007 Post subject: |
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Hi
Not so sure it is.
Carb icing is due to the carbs being so cold that they freeze the moisture in the air as it goes through the carbs, causing lumps of ice to block various jets. Cold air going through at speed takes heat from the carbs. As such it needs pretty cold but damp conditions to occur (fog is probably the worst conditions). Too cold and there is not enough moisture in the air to cause a problem.
Problem tend to be caused by running at speed as the airflow through the carbs is far greater, taking more heat from them. Although the results are less noticeable at speed.
Running at low speed / idle / stopping for a while will likely cure the problem for a short while as the engine heat will soak up into the carbs. Keeping the revs up is likely to make the problem worse and longer lasting.
There is no real easy fix. There are additives that you can use to reduce the problem. You could try other brands of fuel. The production fix is to fit carb heaters (either passing warm engine coolant through the carbs to heat them up, or an electric heater), but not something you can easily do yourself. With carbed cars the easy solution was to have the airbox intake pick up warm air from near the exhaust in winter.
Kawasaki spent a fortune 15~20 years ago recalling all the liquid cooled 4 strokes they had sold in the UK and fitting them with carb heaters (and that meant fitting new carbs to all the bikes). Hate to think how much that cost them.
All the best
Keith ____________________ Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
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D O G |
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D O G World Chat Champion
Joined: 18 Dec 2006 Karma :
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Posted: 13:14 - 16 Nov 2007 Post subject: |
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I vaguely recall that the bloke who dyno'd it about a year ago said that as it was an import it had the carb heaters - or was it the other way round? Hmmm.
I have never cleaned the carbs in the 14months and 9000 miles I've owned it would this help?? |
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Kickstart |
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Kickstart The Oracle
Joined: 04 Feb 2002 Karma :
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The Tot |
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The Tot World Chat Champion
Joined: 11 Jun 2004 Karma :
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Posted: 13:28 - 16 Nov 2007 Post subject: |
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I thought it was a problem endemic to Kawasakis. If it's cold, misty and your bike is bogging down despite constant throttle + adding more throttle at a constant speed, it probably is carb icing. It often does happen at instances where you are at constant throttle opening, i.e. motorway. Had this happen to me up the M1.
Unless it could be your reg-rec/ignition system too. My 250 had similar symptoms what you described but in the mild spring. But seeing that it is winter, carb icing could be the culprit. Silkolene FST seems to alleviate the problem = 10 quid for bottle (1l i think). and it's something like 100ml to every litre of fuel.
Cured the symptoms in the winter - i rode up from brighton to london in mid winter last year in the cold and mist and was fine on the kwak 250.
Although, if you use the search function - everybody last year was diganosing their problems as carb icing when it wasn't, since very few actually had a grasp of the problem. ____________________ The Tot 2007 Yamaha R1 4C8 2002 Yamaha FZS1000 Fazer &
www.youtube.com/Titot182 for your bike gear reviews and pop punk covers
Earl Of Easycore Pop Punk Will Never Die! |
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Ichy |
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Ichy World Chat Champion
Joined: 15 Jul 2005 Karma :
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 15:29 - 16 Nov 2007 Post subject: |
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Carb icing. So you need an engineering solution that will increase the circulating water temperature by altering the thermal dissipation characteristics of your engine in its entirety thereby allowing increased transfer of heat energy between the engine and the carburettors.
But what system could be so feindishly complex yet able to be produced at a reasonable price and be easily fitted and removed by your average motorcycle owner? Could there possibly be such a system within the realms of modern technology It seems insurmountable but I suppose I'd better have a crack at a solution....
Block off half your radiator with a bit of cardboard.
There you go. No charge. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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D O G |
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D O G World Chat Champion
Joined: 18 Dec 2006 Karma :
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Posted: 15:42 - 16 Nov 2007 Post subject: |
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Genius Stinkers, I will try that. If it works, I owe you one, if not, I will hate you for EVER.
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 15:56 - 16 Nov 2007 Post subject: |
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You asked how it works too huh?
Lick your finger and blow on it. Feels cold right?
No imagine that effect magnified by fuel vapourising in fast moving air passing through your carburettor. That's going to be pretty cold yeah? Now imagine the whole effect being concentrated on the end of the throttle needle.
It's not a great step of intuation to work out that this could easily reach the point where the temperature at the tip of the throttle needle gets to below freezing point. This isn't a problem in itself because petrol freezes at a massively low temperature.
What does cause a problem is if that temperature reaches below freezing and there is a high level of air humidity. The moisture coming in with the air freezes on the tip of the throttle needle forming an ice crystal which blocks the main jet preventing fuel getting through.
That's why you tend to get a problem with it on cool, misty mornings/evenings. Not such an issue on frosty mornings because there is usually a clear sky and as such low humidity.
I have long suspected Kawasaki have such a problem with this because of their highly technical airbox design (some kawasaki airboxes can deliver up to 120% of the engine displacement in air per revolution due to pressure wave reflections). I have visions of small clouds of water vapour forming inside the airbox as the pressure waves collapse. Be interesting if someone put a camera in there. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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TUG |
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TUG World Chat Champion
Joined: 12 May 2007 Karma :
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stinkwheel |
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stinkwheel Bovine Proctologist
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crazymotorbik... |
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crazymotorbik... Nearly there...
Joined: 05 Mar 2006 Karma :
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Posted: 18:49 - 16 Nov 2007 Post subject: |
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Hey,
Pro FST works great for carb icing. My GPZ305 was a bitch for running very rough in the winter. Two caps of Pro FST to a tank of petrol made a world of difference
Cheers,
Shaun. |
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cagiva gezzer |
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cagiva gezzer World Chat Champion
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Kickstart |
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Kickstart The Oracle
Joined: 04 Feb 2002 Karma :
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Ben. |
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Ben. World Chat Champion
Joined: 10 Jul 2007 Karma :
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Posted: 20:13 - 16 Nov 2007 Post subject: |
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how do you know whether its carb icing or not? common symptoms? Any way to tell? ____________________ follow my racing season
Race bike - R6
Road bike - sv650 |
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Kickstart |
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Kickstart The Oracle
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Phil_P |
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Phil_P Trackday Trickster
Joined: 10 Nov 2007 Karma :
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Posted: 21:49 - 16 Nov 2007 Post subject: |
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Making your engine run hotter by blocking off the radiator will not make an appreciable difference to carb icing unless you can manage one of two things
1) You can transmit enough waste heat to the carb body to prevent ice from forming. Unfortunately, most bike makers go to a lot of trouble to insulate their carbs from engine heat to prevent fuel evaporation problems.
2) You can warm the inlet charge (in this case the air) to a point where the drop in temperature still allows the charge temp to remain above dew point. Again, unfortunately, most makers take their inlet air from a point that isn't affected by engine temp, as a colder charge means denser air means more power.
Blocking off the radiator may give you some extra heat getting to the carbs, but you are forcing your bike to run hotter than design, especially if you get stuck in traffic and have reduced air flow. Boiled coolant and popped off hoses anyone?
The reason Land rovers and similar had radiator blinds, is that even with a thermostat in circuit, the engine was still being over-cooled in cold weather, it had nothing to do with carb icing (they used them on diesels too, and they don't suffer from it.
Your best bet in the absence of carb warmers is to duct some air heated by waste heat into the air box, perhaps from behind the cylinders or radiator. You can get corrugated metal hose from a car part place that will do the job nicely, then just splice it into one of the existing air pipes leading to the air box, or cut a new hole and silicone it into place.
Light aircraft which fly around in circumstances where carb icing is much more likely than on a bike, (and the effect is also potentially fatal), have a lever in the cockpit that does exactly the above. Carb heat is switched on whenever carb icing is really best avoided (like final approaches for instance). ____________________ It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96 |
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andys675 |
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andys675 World Chat Champion
Joined: 08 Feb 2007 Karma :
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Posted: 23:24 - 16 Nov 2007 Post subject: |
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crazymotorbiker wrote: | Hey,
Pro FST works great for carb icing. My GPZ305 was a bitch for running very rough in the winter. Two caps of Pro FST to a tank of petrol made a world of difference
Cheers,
Shaun. |
totally agree, also cleans out your sytem, my old 350 YPVS was awful, now it ticks over cold! |
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fenton |
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fenton World Chat Champion
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baldy |
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baldy World Chat Champion
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Whosthedaddy |
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Whosthedaddy Super Spammer
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Posted: 20:47 - 18 Nov 2007 Post subject: |
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Interesting read lads with some cheap fixes like the additives. I am not lying if I told you that the idea of carb icing with the 7R has scared the pants off of me when the temperatures in the morning have been getting lower and lower.
Cold and damp worst case scenario, gotcha.
What to do if the bike packs up due to it, is it just wait at the side of the road and wait for the little bits of ice to melt? ____________________ Current : MSX 125 Past : CBR 900RR Monkeybike : c50 LAC : ZXR750 H2 : FZR600 : ZX7R P3 : YW100 : TRX850: Trophy 900 T309 : GSXR 600 L0: Monkeybike : XJ6S Whosthedaddy |
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Bardeey |
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Bardeey Scooby Slapper
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Kickstart The Oracle
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map |
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map Mr Calendar
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Old Thread Alert!
The last post was made 16 years, 202 days ago. Instead of replying here, would creating a new thread be more useful? |
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