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So I had my '74 R90s at the track on Monday. My group was the first to go out and as I hit the starter button, nothing.

Just a barely audible click from the frame mounted starter relay. A week ago I had the Valeo starter out, replacing the armature and planetary gear cover, and bench tested and installed. I rode the bike a few times and no issues.

Anywhoo, For the first time in about 30 years I actually used the kickstart and I was able to play all day.

Got home last night and did some checks. I should point out that the entire wire harness is less than three years old, but my first check was to look at the relay. Removing the black wire, I checked voltage on the relay contact and verified 12.7vdc when the starter button was pressed.

I then re-connected the black wire to the relay and removed the same wire from the starter solenoid. Again, a voltage check was performed but this time, only 12.1vdc was reaching the solenoid. hmmmm?

I ohmed out the wire from the relay to the solenoid and it shows less than .01ohm so.....

I have the starter out and taken apart and the solenoid coil. (measured from the solenoid contact to case ground shows a closed circuit (can't remember the exact resistance), showing the solenoid coil isn't open.

Tonight I'll bench test the starter, but the question is 1) why would the voltage be different at the solenoid end of the black wire than from the relay output itself? 2) If the solenoid coil is good on the starter, and I have 12volts, why won't the solenoid engage and run the starter?

thanks,

jimmyg

So if I am reading this correctly you are dropping .6v across the contacts of the relay, which may or may not be an issue other than pitted or dirty contacts. You indicate that you have 12v at the solenoid, but the starter is not engaging. Since the contacts in the solenoid allow battery voltage to turn the starter I would say your solenoid points are broken off. If you can feel the solenoid pull, then the contacts are not completing the circuit.

I'll know more tonight, but like I said, I measured 12.7vdc at the starter relay male lug (black wire removed).
I then reconnected the black wire to the starter relay and removed the other side of the same wire, at the starter solenoid. I ran the same test and observed .6vdc less. Not a big deal I guess, but when re-connected, the starter solenoid doesn't pull in.

It seems strange that nothing at all happens at the starter because the solenoid coil measures continuity and I have at least 12volts going to it.

If I manually push the solenoid in to engage the contacts, I measure .3ohms. So if the solenoid pulled in as expected, I would expect the starter to spin.

I had no issues with this starter for the last 10 years, but a few weeks ago, the planetary gear cover came off, and shorted out the armature. New armature, new cover, everything cleaned and lubed. And was working perfectly until this Monday.

Strange for sure.

I'll let you know what further discoveries I make.

jimmyg

How old is the battery? I would do a load test on the battery before digging into the starter. I have checked many a battery that shows correct voltage but would have low cca.

thanks bluesman,

Battery is a brand new Westco AGM. I put it in about a week ago.

But that's not to say it's not an issue. I'll do the bench testing with a different battery as I have a few good spares sitting around. If the problem stays with the bike battery, I'll definitely have it load tested.

I do remember working on a /5 a few years ago. Owner just put in a new AGM battery, but the starter wouldn't engage. The interesting thing with that scenario is that just turning the ignition on, the battery voltage would drop, working it's way down to about 9vdc.

Took a week's troubleshooting before I finally took the battery to have it loaded tested. Yep. Crap battery. And yes, it was made in China.

jimmyg

So if you had a test lead you could connect to solenoid and tap bat + with other end, should pull then. No need to remove starter to test.

Jimmyg, you said, "It seems strange that nothing at all happens at the starter because the solenoid coil measures continuity and I have at least 12volts going to it."

I infer that this measurement isn't under load. If there is no load, the measurement means very little.

I bench tested the starter last evening and with another good battery, the solenoid still doesn't pull in. Again the measured resistance from the solenoid terminal lug to ground is 1.0 ohms, so I would expect it to pull in, unless there is a mechanical drag of some kind.

Maybe the smart thing is to pick up another Valeo solenoid.

thanks,

jimmyg

Sounds like your solenoid is toast. 1.0 ohm resistance on a coil is way too little. I would expect something around 50 ohms or higher. Since the starter is on the bench, have you applied power to it by passing the solenoid to insure it spins.

jagarra wrote:Sounds like your solenoid is toast. 1.0 ohm resistance on a coil is way too little. I would expect something around 50 ohms or higher. Since the starter is on the bench, have you applied power to it by passing the solenoid to insure it spins.

It definitely spins if I bypass the solenoid.

1 ohm seemed pretty low to me also. Thanks for clarifying.

Also, something odd that I've never seen in all the starters I've torn apart; the solenoid terminal that connects to the brushes, has a short between it and the solenoid case.

jimmyg