QuestionI just bought a 1982 Honda 450 blackhawk and it hesitates or will not hold a even speed on the road. I feels like it is missing or staving for fuel. I checked the plugs and they are good, what cold it be?
AnswerLarry, your 26 year old Nighthawk probably needs a good carb clean and inspection.
http://www.cmsnl.com/honda-cb450sc-nighthawk-450-82-us_model456/partslist/E++18....
The left carb has a diaphragm on the side to prevent backfiring. If the diaphragm fails, you get a bad idle and backfiring and loss of power.
The fuel tank petcock has a vacuum operated function, using a diaphragm and other o-rings and parts. When this diaphragm fails you get a bad idle and greatly reduced fuel flow to the carbs, reducing the power.
http://www.cmsnl.com/honda-cb450sc-nighthawk-450-82-us_model456/partslist/F++13....
Any vacuum lines coming from the carbs to other components need to be checked for cracks or leaks.
You could have a failing spark plug cap, too. They should measure about 5k ohms, after being removed from the plug wire end.
If your air filter element is the original one, that could be another problem, as they do either plug up or fall apart, causing changes in the air flow to carbs, which are calibrated for a correct air cleaner and stock mufflers.
And there could be other issues causing this problem.... You didn't state the miles on the odometer, compression readings or other history on the bike.
Bill Silver
