'77 R100S: Neutral or Clutch Switch?

[zombiepotatosalad]

'77 R100S: No Start. Neutral or Clutch Switch?

I tried checking to see if it would crank before buttoning up the headlight bucket, and no joy. It cranked yesterday.

I tried shifting it into 1st and neutral again, which is how I got it to crank again last time. The neutral light is on, and it cranked when I pulled in the clutch. Now, the neutral light is still on, but it won't crank, even when I hold the clutch. Is it the clutch switch, or neutral switch that's bad?

I also bought a new starter relay, just in case, but the old one still worked.

 

[RPGR90s]

Start by process of elimination. Go through the schematic to bypass the starter switch, then the starter relay, until you're eventually, you're using a manual switch to pull in the big solenoid on the starter.

 

[zombiepotatosalad]

Start by process of elimination. Go through the schematic to bypass the starter switch, then the starter relay, until you're eventually, you're using a manual switch to pull in the big solenoid on the starter.

I'm autistic, I need details. Eliminate what? Bypass how?

 

[stevenrankin]

starter relay

The quickest test for now is to just change the starter relay. I will have to look at the wiring schematic to figure out what color wires to check for current flow That is if changing the relay doesn't help.

The headlight will have to come out so you can get inside the shell. The green light is on so I am going to assume it is not the neutral switch but could be the clutch interlock switch. St.

 

[jimwjarmour]

Hi ,guys starter relay

The quickest test for now is to just change the starter relay. I will have to look at the wiring schematic to figure out what color wires to check for current flow That is if changing the relay doesn't help.

The headlight will have to come out so you can get inside the shell. The green light is on so I am going to assume it is not the neutral switch but could be the clutch interlock switch. St.

the only time i can remember my 1977 r100s would not start was after i completed a service in which i removed the starter relay and cleaned connection both male and female reassembled with electrical grease reassembled tank seat etc told the wife going foe a wee test run ,if im not back in 10 minutes come look for me said as a joke got to bottom of street bike died cant remember if dash lights were on but no starter ,this was a long time ago 30 plus years, so wife came looking for me pushed her home bike not the wife , pulled tank and did various checks, found that the large red wire going into the bottom of relay had been pushed out when i replaced the relay never had a problem since ,a few years ago i replaced the relay with a upgraded type double checked wireing going into bottom of relay block, hope this assists , happy new year to all Jimmy

 

[zombiepotatosalad]

The quickest test for now is to just change the starter relay. I will have to look at the wiring schematic to figure out what color wires to check for current flow That is if changing the relay doesn't help.

The headlight will have to come out so you can get inside the shell. The green light is on so I am going to assume it is not the neutral switch but could be the clutch interlock switch. St.

Starter relay swapped, still nothing. Where is the clutch interlock switch, and how can I test it?

 

[stevenrankin]

Clutch interlock and neutral switch

From what I can see the two switches are part of a ground loop. The ground completes the circuit for the starter.

Check the bottom wiring block of your starter relay and make sure the wires are in good shape and they are actually making contact inside of the plastic block with the relay terminals. Just because the new relay or old one plugs into the plastic block doesn't mean the terminals are connecting. St.

 

[stevenrankin]

Will

Will the bike turn over in gear with the clutch pulled in? Didn't you say it did at one time in another post? St.

 

[guenner]

If the neutral light is on while in neutral gear and otherwise it is off, the neutral switch works.

Besides a malfunctioning clutch switch, you may have a problem with the starter switch.

Do you have a voltmeter to do some tests?