Hi a quick question took the plunge and got a beautiful Road King (which replaced my Vulcan), it ran perfectly all summer (2005 custom), but when it got below 40F (Montreal...its cold already) it began sputtering and backfiring.I checked the plugs and the rear cylinder is running too rich, black sooty while the front plug is perfect, I replaced them with new ones and the same thing happened. The bike is carburetored and runs perfect except in cold weather. I plan to adjust the mixture by adding EZ flow (thumbscrew adjuster) this winter. but to your knowledge is there anything I can check or change that would make the rear cylinder run better? thanks for your expertise. as always its very appreciated, Mike
newbie need a bit of advise please
- Thread starter xenarocky
- Start date
2000classic
Active Member
You may have a bad plug wire going to the rear cylinder. I would check that out next.
Rich rear cylinder and clean front cylinder could be a jetting problem or an intake leak on the front cylinder that was over compensated by adding more fuel and sooting up the rear plug.
Check the intake seals for leaks.
Harley Davidson Community
As i saw your second post with the same info apart from you added that after about 20 minutes it ran ok
next question how much humidity in your area
I have a wee suspicion that you may be suffering from carb icing as the engine gets hot it will produce enough heat to prevent the ice from forming
the ice forms as the air is drawn through the throat of the carb the shape of the carb throat will determine the amount of chilling the air will receive further chilling is caused by the atomisation of the fuel as it exits the jets this will cause the moisture in the air to form ice normally at the coldest point
often with this type of carb the slow jet gets blocked by ice weakening the overall mixture bike will splutter and backfire possibly die
Brian
next question how much humidity in your area
I have a wee suspicion that you may be suffering from carb icing as the engine gets hot it will produce enough heat to prevent the ice from forming
the ice forms as the air is drawn through the throat of the carb the shape of the carb throat will determine the amount of chilling the air will receive further chilling is caused by the atomisation of the fuel as it exits the jets this will cause the moisture in the air to form ice normally at the coldest point
often with this type of carb the slow jet gets blocked by ice weakening the overall mixture bike will splutter and backfire possibly die
Brian
thanks however this is hapening between 35-45 degress F so above freezing and its reaaly annoying as difficult to drive at first, someone suggested the spark plug wire, but then why would it run OK after 20 minutes and all summer? It does have a non stock battery but I have it on the tender in a garage every night and have purchase a new battery on which I'm waiting. I was thinking to move to a hotter plug for the rear cylinder?
Carb icing usually occurs between +3 and + 13 degrees Celsius below +3 the moisture in the air is already frozen so it can not freeze in the carb
the carb works in a similar manner as the compressor in a freezer to chill the air although in this case the compressor is the engine and the air being drawn through a narrowing passage causes it to chill
Brian
the carb works in a similar manner as the compressor in a freezer to chill the air although in this case the compressor is the engine and the air being drawn through a narrowing passage causes it to chill
Brian
There are some fuel additives that are said to help however the cause is the design of the carb throat the best way i found to get around the issues i had with the carb was to replace it with a mikuni hsr 42
another fix would be to move to an area with lower moisture content in the air
silkolene pro fst was created by silkolene at the request of kawasaki uk to help overcome the icing problem with the keihin carbs
Brian
another fix would be to move to an area with lower moisture content in the air
silkolene pro fst was created by silkolene at the request of kawasaki uk to help overcome the icing problem with the keihin carbs
Brian
This could be a case of carb icing. Carb icing is a comon problem with light aircraft and in fact is the cause of many an unplanned off airport arrival sometimes with fatal results. Light aircraft have a carb heat control which directs heated air from the exhaust system into a kind of air to air heat exchanger to solve this problem. Not sure how you could do it with a bike.