starter motor struggling

Hi all, I have a 1983 Honda Nighthawk CB650SC (dohc type) with a
starting issue. The starter motor labours and kind of pulses on and
off, reluctantly starting the engine (usually). If I turn off the kill
switch (which just knocks out the feed to the coils but allows the
starter to turn) the starter motor turns fine, so it's not a problem
with the switch. The battery and charging system are fine. Any ideas?

Thanks for sharing your technical know-how with the rest of us, Adam

 

It sounds to me as if the ignition timing has advanced itself a bit -
the plug in a given cylinder is sparking too far before TDC and when the
charge ignites it is trying to push the piston back down the cylinder,
fighting the action of the starter motor. Go check your points.

 

Clean the battery terminals first.
Check that the battery is fully charged and not stuffed.
Clean all other connections including the starter solenoid.
Check the starter motor brushes.

Or GAMI.

 

I agree with the Pipster. Deffo advanced timing is the primary cause of
that. The symptoms don't point to anything else.

 

Thanks for all the helpful suggestions. It's an electronic ignition
bike rather than points, otherwise I agree that would be a prime
candidate. I'll clean up all the contacts and try again. I took the
kill switch apart yesterday. Twas a bit grubby inside, but not
terrible. It's now reading 3 ohms when set to run, which I guess is ok.

 

So, I cleaned up the starter switch, took the starter motor to pieces
(it was seriously grubby and had little bits of something - worn out
brushes? - floating around), new HT leads and plug caps. It does it a
lot less now, but it's still there, especially if you try starting
with the choke on. I can't figure out the relevance of this. Is it
harder to turn over an engine like this with a plunger type choke
pulled out?? Can't be, surely?

 

Check the fucking timing.

 

It's electronic ignition - the only way I can think of doing this is
buying a strobe gun and looking for timing marks on the end of the
crank whilst the engine is running. Is that what you suggest?

 

That's exactly it. Get the thing spinning over freely on the starter
with no plugs in and point the strobe at the timing marks. Not sure of
exactly what timing marks will be on your model, but a w'shop manual
will show you.
Oh, without plugs in the head, make sure you put the plugs into the caps
and sit them on the cyl head so they spark to earth. Avoids the chance
of blowing the ignition unit.

 

But don't spray lots of carb cleaner around at the same time, it makes
for rather a big bike bbq.

DAMHIKTIJDOK

 

Go on then - tell.

 

Sorted!