• Enter the March CB750 Supply gift certificate giveaway! It's easy... Click here, post something, and you're entered into the drawing!

Neutral Indicator always on (even with new switch)

Crabnab

CB750 Member
Messages
10
Reaction score
0
Points
1
Location
Austin, TX
Bought a '76 CB750F from a guy who had done most of the restoration work. It's marginal work but the bike looks great and runs pretty well as well. Just minor things remain. One of those things is a Neutral Indicator that is always on, regardless of Neutral or In-Gear. Seller claimed it just needed a new switch. Earlier today I replaced the switch with a new one - still in package from Honda.

I checked the continuity of the switch before I put it in the bike and it seemed to be correct- full continuity when ball was not depressed, 0 continuity when ball was depressed. Replaced the switch- exact same behavior.

I've also checked to see if the wiring is correct by taking the connector off the switch entirely thereby breaking the connection, it indeed does turn the light off. When I ground the wire to the frame it turns back on again so the circuit appears to be correct.

Is there something inside the engine crankcase I need to align? If so, is that a do-able job for a novice? Any guidance on what I should be looking for would be greatly appreciated.
 
Is the switch seating all the way into the case? The shift drum is what depresses the neutral switch. It looks either like the switch isn't going in all the way or there is some severe wear on the shift drum in which case the engine has to be removed and the cases split to get inside to replace the drum.
 
Is the switch seating all the way into the case? The shift drum is what depresses the neutral switch. It looks either like the switch isn't going in all the way or there is some severe wear on the shift drum in which case the engine has to be removed and the cases split to get inside to replace the drum.

Is there a sure fire way to determine if the switch is in all the way? Based on visual comparison, I'd say the new switch is in about as far as the old one was before I removed it. Then again, the old one wasn't working either. Is replacing the shift drum even an option anymore, if so, is it worth it for this repair? Also, what are the long term effects if I just let it go?
 
If it was me I would just disable the light. All it is there for is to tell you when you are in neutral. You need to leave the switch in as it also functions as a detent to let you feel neutral position. You would have to find a good used drum as most parts are discontinued.

When the switch is all the way in, the little hold down piece of metal should be about parallel with the motor, it shouldn't be at an angle when the bolt is tightened up.
 
Hrm. Great tip- now that you mention it, the retention clip is at a bit of an angle. Any tip on 'encouraging' the switch to travel further into the case? The exposed surface of the switch appears to be of some kind of softer than metal material- ceramic? Either way- I'm hesitant to smack it with anything.
 
Lube up the oring with some oil, snug up the bolt and I have tapped on the edge with a rubber hammer but generally they should just slide in with very little effort. Make sure it is in neutral so you aren't fighting pushing against the spring in the switch. It should slide right in. It sounds like it isn't seating. Take the oring off and see if it fits any farther or easier into the case, if it still doesn't go in then take a look in the hole and see if there are any burs or sludge keeping it from going in.
 
So, I took the new switch out so I could beat on the old one if it came to it. Since they are reading the same in my "out of the bike" continuity test, I figure the same results should be expected when they are "in the bike."

Anyway- took the o-ring off and it definitely went in further than I had been allowing it. Unfortunately, same behavior- indicator light is always on. My next step is to check continuity while the switch is in the bike and record the readings from neutral to in-gear. Maybe that will tell something.

I've never looked at the electrical diagrams- is it possible that the switch is still providing 'some' current even while the ball is depressed? Does the original circuit require less current to dim/extinguish the original indicator lamp? Is it possible that I need to resist the circuit somewhere (if some current is getting through) since the original instruments have been replaced with aftermarket LED-based indicator lights?
 
The switch is either on or off there is no in between and no dimming of the light occurs. All the switch does is ground the circuit when it is in neutral. When it goes into a gear it pushes the ball of the switch in and it breaks the ground of the light circuit. That is on stock, I have no idea what your led gauges need in order for your light to work. When you check the switch in the bike in neutral you should have continuity...when you put it into ANY gear it should break the continuity.
 
Well. Bummer. I'll check continuity while it's in the bike and see what the meter reads.

I just find it hard to believe that the shift drum can be so worn on an engine that allegedly has only 20k miles on it. There isn't any kind of alignment I need to do of the drum, correct?
 
Take the switch back out with the trans verified in neutral use a probe ( small screwdriver, ect.) into the lower case and check for the shallow countersunk hole in the drum, there might be sludge or something else obstructing the hole, Dirtdigger covered about everything else.
 
There is no alignment or anything you can adjust. I have never seen one wore out either but the previous owner did "marginal" work so all bets are off.
 
OK- I have good news! It was a combination of issues. The old switch is in fact faulty. While it was in the bike, the continuity test yielded weird results- the needle was hopping all over and only lost continuity when the ball was depressed to the extreme.

Additionally, the O-ring that was on the old switch seems to be either preventing the switch from being mounted fully inside the case or is too thick. I don't trust myself not to break my new switch trying to force it further in with the existing O-ring so I'm in search of a thinner o-ring to replace it.

Is this a fool's errand?

OH- I suppose I should mention, with the new switch (without the O-ring) the switch functions as intended and it shutting off the indicator lamp while in gear.
 
Last edited:
I think with enough lube and a little persuasion it should seat like it is supposed to. You can always go to hardware store and look for orings. If you cant find a thinner one look for a smaller diameter oring and when it stretches it will get thinner.
 
Thanks to you both- especially you dirtdigger. I managed to find a 'one size smaller' o-ring and popped that bad boy on the neutral switch and dunked the whole thing in lubricating oil. Switch snugged right in, stayed in place and voila we are back in business. Neutral indicator is working as intended. Thank you so very much!!

My next projects:
- Tune the carbs- maybe, I honestly don't know if this is within my capabilities
- Determine why there is a small amount of white smoke wisping out of near the exhaust port on the 3rd cylinder.
 
Back
Top