CB750K Starter Button Fix? (right hand switch)

[saw750]

I was replacing the cable on the old 1976 CB750K and I noticed that the starter button stuck. After further investigation, I discovered that the internal housing surrounding the button itself was brittle and cracked in several places.

The wires are intact and in good shape its the lil rectangle plastic surround that is junked and shattered

Is there a replacement available??? (off other models?) or do i have to replace the entire right handle bar switch? (I see OEM on ebay for $100 +/- ugh!)

I know its not the end of the world there is always kicken but still i would like to have this functional.

Is there a hack available? I dont care whats going on inside the switch as long as it works

thanks in advance - saw

[Re-run]

Partsnmore.com has the button kits. I am not sure if it will have that plastic piece but the kit is pretty inexpensive.

[idahobilly]

There is a seller on EBAY who sells a repair kit that contains a new plastic button attached to a brass post plus a very small spring.I used his kit to fix my starter button and it was pretty simple. hardest part was removing small screw that holds button in switch.Cost of kit with shipping was $11.75. Way cheaper than nos switch or used pos ebay switch. Look for "dgs38" under seller.  

[LukeM]

Kick starting a 750? If the motor is in good tune, maybe, but I can't imagine doing that for very long...

Especially if the bike's been sitting for a while, and that fuel manifold valve thing isn't letting gas get to the carbs unless there's vacuum to the valve...  Whew, I'm scaring myself here.

I saw a similar thread a while back about starter switch buttons.  Ebay may be able to help here.  Good luck.
Luke M

[saw750]

the piece labeled switch housing is what i am missing. it completely fell apart

[LukeM]

Oops...didn't realize that.  Sorry.
Luke M

[saw750]

a two prong momentary switch from radio shack will work but how would you wire it??

[LukeM]

DISCLAIMER: I am not responsible for any damage done to your bike as a result of this post. This post is provided as informational and speculation only.  

There should be a good copy of the wiring for the bike, perhaps in the Factory Service Manual on this site. Find the wires going to the start switch, and tap in at that point. Being that it's on the low current side of the starter solenoid, I'm guessing the current through the switch is probably fairly low, and much less than on the starter side.  However, it's better to be safe than sorry. So, if it were me, I'd put a normally open momentary contact pushbutton switch in there, that can handle 4-5A.  That's the engineer in me talking.

On my son's CB550, the wires for the start button were push-on contacts on the control assembly.  It might be the same for you. I'm about 800 miles from my bike at the moment, or else I'd run to the garage and check.

I hope this helps.  Good luck.
Luke M

[LukeM]

I took a look at the FSM for 79-83 CB750s, and on page 238 of that PDF it shows a DPST switch for the start button.  That means a single pole momentary switch won't work.  It looks like one half of the switch energizes the solenoid, and the other half supplies power from the battery to power the solenoid.  You'll also see a 30A fuse in line with the start switch.  Might be overkill, but they used that value for a reason.

Engaging the start switch appears to get 12v from the battery, so it'll loop through the switch, provide power for the solenoid, and finally close the low-current side of the solenoid.  This engages the high current side from the battery to the starter, and from there, things go whir and hopefully VROOM until you release the switch.

Either that, or it's all magic somehow.  I'd feel safer just getting the appropriate factory switch from the dealer, or EBay, and using that. Less wiring and modification, and they've done the engineering already.

Luke M

[saw750]

soooooo what would work? couldnt a couple of the wires be attached to one pole?

here is the diagram

[LukeM]

OK, I goofed again.  I thought it was a DOHC model.  This diagram you posted is different.
This one is a bit simpler, but does essentially the same thing. If the start switch is at the top next to the Emergency and Headlight switches, then it's a simple Normally Open SPST switch. It does have voltage for the low current side of the solenoid.

So, apply the same disclaimer used on an earlier message, and find a good pushbutton switch rated to 5 amps or so, and see if it works.  You'll connect the switch to Red/Green and Red/Yellow.

Good luck.
Luke M

[Logan]

i have a similar problem but the kid before me hacked the wire harness up, i managed to get it all hooked up but when i try to"jump" the red/green to the red/yellow nothing happens but when i stick a screw driver between the leads on the solenoid the starter cranks right over, any ideas what could be goin on? bad solenoid?

[sgtslag]

I've had errors on the wiring diagrams as far as color codes go...  Try measuring the voltage across the Red/Green and Red/Yellow wires:  if there is 12V across the two, then the solenoid is likely bad, or there is a bad connection.

To test the solenoid, apply 12V across its coil leads, and listen to see if it "clicks", which would indicate the solenoid is closing the switch contacts.  If this fails to produce the click sound, the solenoid is bad (to verify it is failing, connect an Ohmmeter across the switch leads:  when the 12V is applied across the coil, the switch contacts will close, and the Ohmmeter will read less than 3 Ohms, indicating a short; disconnect the 12V, and the Ohmmeter should indicate infinite Ohms, or an open circuit).  Cheers!

[LukeM]

If you use the screwdriver to arc across the two large posts on the solenoid, and it actuates the starter, that usually points to either a bad switch on the low-current side of the solenoid, or bad contacts inside the solenoid.  Normally you'll hear a *click* when the solenoid engages.  

It _is_ possible to take the solenoid apart and clean the contacts.  However, it may be more advantageous to find a factory replacement (if they exist) or perhaps retrofit an external solenoid.  Older Ford automobiles used to use a solenoid that mounted on the inner fenderwall.  Perhaps something this size or smaller could be wired in.

Hope this helps.
Luke M