Honda CB 750 with No Spark

 I am trying to get my roomates 1970 Honda CB 750 running.  I am having
problems getting spark.  I have checked the points and they are good.
I have changed the spark plugs.  What else should I test?  The coils
look like they have been changed recently, but I have not tested them
yet.  Are there any kill switches I should be aware of?  I have a
charged battery and the bike cranks, but no spark?  Any suggestions?

 
There is a sstandard kill switch on the handlebar.  Don't just check
to see that it is in the "run" position.   Check the circuit for
continuity in both the run and the off positions.

I would also look hard at the coil circuit, since the coils were
recently replaced.

Finally, if the ignition wires are the original oem ones, they should
probably be replaced just on general principle, since they are now 37
or 38 years old.

Good luck!

 

You haven't mentioned the condenser(s).  Have you
got a test light?  The points are opening and closing,
right?  When the circuit is working right you should
be able to open and close the points with your finger
(or a screwdriver) and get a big spark every time...
no need to crank to test.

Often there is an ignition resistor, meant to lower the
voltage when the vehicle is running (battery voltage
goes *way* down during cranking).  If this resistor
is open, you will get no primary coil voltage (through
the points).
__
Steve
'06 FXDI
KI5YG
#0627
.