Starter button issue on CM400

Gnash · 07-30-2008, 05:01 AM

I have an 81 Honda CM400C. When I first got the bike, I had to start it by putting a screwdriver on the two posts of the solenoid. I got a parts bike(motor) and I had to do the same thing with it! Start button didn't work on either bike! So, now I have the motor from the parts bike and I still have to start with the solenoid method. When I hit the starter button, my headlight dims. What are the odds of 2 bikes having the EXACT problem?! I haven't found a short. Do I need a new solenoid? New ignition switch?

rocksolid · 07-30-2008, 06:47 AM

The starter button is the weakest part. Take it apart and find out if it's bad.
Here is a link on fixing starter buttons.
http://www.rattlebars.com/mtz/starter.html

mydlyfkryzis · 07-30-2008, 06:47 PM

The starter button is a 2 pole switch. The headlight IS supposed to go out when you hit the starter. That allows more current to be available for the starter and ignition.

If you check a schematic, you can see the headlight circuit is tied to the starter switch.

It sounds more like the solenoid is bad. The starter switch only activates the starter solenoid (and turns off the headlight). If the solenoid isn't engaging, then check the wiring on that, check the coil for resistance.

rocksolid · 07-30-2008, 07:28 PM

Here is a pic of the guts of the start button. As you can see, it's very delicate.

The contacts in the base wear, drop below the plastic mounting, and stop making connection. A little light sanding brings them up so the switch can work again. Even if the solenoid proves to be bad, rebuild the switch anyway. Chances are that a 1981 bike has some wear on the start switch. 'Cause getting stranded really sucks. lol

Gnash · 07-30-2008, 11:05 PM

I've had three different solenoids on there and no go, so I'm gonna clean that switch up. When I first got the bike, I remember the key switch getting hot. There is now a burn mark on the ignition, from it getting hot.

rocksolid · 07-30-2008, 11:27 PM

Sometimes the start switch gets shorted and causes heat in the ignition switch. The part that carries the contacts can melt as it's only soft plastic. I'd definitly clean the start button, but have a look at the base on the ignition switch too. It's a separate piece from the ignition tumblers, so you might be able to pick one up used. The contacts in the ignition switch are only copper stampings, so when they get hot, they melt the plastic that holds them in place and get off track.

07-30-2008, 05:01 AM	#1
Gnash Master At Arms Join Date: Jun 2008 Posts: 120	Starter button issue on CM400 I have an 81 Honda CM400C. When I first got the bike, I had to start it by putting a screwdriver on the two posts of the solenoid. I got a parts bike(motor) and I had to do the same thing with it! Start button didn't work on either bike! So, now I have the motor from the parts bike and I still have to start with the solenoid method. When I hit the starter button, my headlight dims. What are the odds of 2 bikes having the EXACT problem?! I haven't found a short. Do I need a new solenoid? New ignition switch?

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07-30-2008, 06:47 AM	#2
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	The starter button is the weakest part. Take it apart and find out if it's bad. Here is a link on fixing starter buttons. http://www.rattlebars.com/mtz/starter.html

07-30-2008, 06:47 PM	#3
mydlyfkryzis Gadget Freak Join Date: Jul 2008 Location: Northern NJ Posts: 339	The starter button is a 2 pole switch. The headlight IS supposed to go out when you hit the starter. That allows more current to be available for the starter and ignition. If you check a schematic, you can see the headlight circuit is tied to the starter switch. It sounds more like the solenoid is bad. The starter switch only activates the starter solenoid (and turns off the headlight). If the solenoid isn't engaging, then check the wiring on that, check the coil for resistance.

07-30-2008, 07:28 PM	#4
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	Here is a pic of the guts of the start button. As you can see, it's very delicate. The contacts in the base wear, drop below the plastic mounting, and stop making connection. A little light sanding brings them up so the switch can work again. Even if the solenoid proves to be bad, rebuild the switch anyway. Chances are that a 1981 bike has some wear on the start switch. 'Cause getting stranded really sucks. lol

07-30-2008, 11:05 PM	#5
Gnash Master At Arms Join Date: Jun 2008 Posts: 120	I've had three different solenoids on there and no go, so I'm gonna clean that switch up. When I first got the bike, I remember the key switch getting hot. There is now a burn mark on the ignition, from it getting hot.

07-30-2008, 11:27 PM	#6
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	Sometimes the start switch gets shorted and causes heat in the ignition switch. The part that carries the contacts can melt as it's only soft plastic. I'd definitly clean the start button, but have a look at the base on the ignition switch too. It's a separate piece from the ignition tumblers, so you might be able to pick one up used. The contacts in the ignition switch are only copper stampings, so when they get hot, they melt the plastic that holds them in place and get off track.