QuestionI have a 1978 Honda CB400A hondamatic with 20k miles. It will start, idle, and rev great, but when put under load with a person riding it bogs down and wont pull you. When in gear on the center stand it runs great.I have adjusted the valves, cleaned and rebuilt the carbs( a couple of times), replaced the intake seals, checked the timing, replaced the air filter,spark plugs and cable ends, has good spark, I am out of ideas.Please help?
AnswerRod, what are your compression readings?
The spark advance is electronically controlled, so needs to be checked as much as the stock idle ignition timing.
Stock air filters? If not, then it will need re-jetting on the main jets.
CB400A models had a history of ignition system woes either the stator/pulse generator coils or CDI control module. Check the coil primary winding resistance values.. hot and cold.
http://www.cmsnl.com/products/30400-417-014-cdiunit_30400417004/ shows that the part number was superseded/improved.
When engines break down under load it is generally either lack of spark advance, coil failing on output or carburetion too lean/rich.
Make sure you have the primary/secondary main jets in the right places, if they are the same dimension part. Some Hondas used the same sized jet in both places and some have a bigger/smaller jet setup.
Does it shift properly from L to D? Always start in Low, of course.
Bill Silver
