Re: 1980 CB750F - Starting Issue Advice needed.

Posted by LukeM on Sep 05, 2012; 6:04pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1980-CB750F-Starting-Issue-Advice-needed-tp4028643p4028729.html

This is not important for now.  Having the spark units hanging off the frame shouldn't have anything to do with your engine cranking problem.

You can check a schematic of your bike to see if there's a ground wire on the harness, or if the unit is grounded through the frame.

So, we've ascertained that the starter spins freely when out of the bike, but doesn't spin well when installed.  It's possible that there are issues with the gears in the starter clutch on the left side of the engine.  Stupid question: is the motor seized?  Can you turn the engine over by push starting it, or by putting a ratchet wrench on the crank and spinning the motor by hand?

To get to the starter clutch, center stand your bike, get a small catchpan, and remove the left side cover.  You'll see a couple of reduction gears that connect the starter to the crankshaft.  You'll also have a little bit of oil that drips out when you take the cover off.  This is normal.  Make sure the gears spin freely in one direction, and resist going the other direction. You can also leave the cover off and see how the starter motor spins the gears.  This may help diagnose your problem.

Hope this helps.  I'm doing this from memory, as I've been without my CB750 for 2 years now.  *sniff*  Yeah, I miss it.

Luke M