Checking the idle on a CB400A/CM400A/CM450A Hondamatic

[Maraakate]

I made a small video showing how a properly tuned Hondamatic should respond.

When you do this check you really ought to use a portable tach. However, it can be done ear.

If you can't achieve a good idle there are a number of things it could be such as:

• Dirty idle jets
• Shrunken or missing passage plugs
• Pilot mixture screws with broken/bent tips, missing the o-rings or washers, or o-rings needs replaced
• Air leak from insulators, air box rubbers, their clamps or insulator o-rings. Inspect insulators carefully for cracks.
• Faulty ignition system
• Valve clearances way too tight or way too loose
• Poor compression
• Leaky valves

@LongDistanceRider has a thread on rebuilding the carburetors here. I have a thread on diagnosing the ignition system here.

EDIT: By request and some slight confusion, I have added a second video that shows the use of a portable inductive tach. In my opinion, a tool everyone here should have if they are serious about maintaining their vintage bikes.

 

[Maraakate]

By request and some slight confusion, I have added a second video that shows the use of a portable inductive tach. In my opinion, a tool everyone here should have if they are serious about maintaining their vintage bikes.