Funky starting quirk

[XJkid]

Lately my bike is being problematic on first starts in the morning. It turns over just fine, but doesn't fire until the moment I release the start button.
what's up with that?

[DEEBS11]

XJkid, your battery is the most common issue. Enough amperage to turn the starter motor but not quite enough to power the ignition system at the same time. Release the starter motor and there is now enough current for a split second to fire the still moving engine. Just enough to start it. Also note there could be some resistance in the electrical harness as well. The most common failure other than "plug in " connectors is right at the battery terminals. Make sure they are clean and tight. If the battery is old or does not get charged on a regular basis over the winter months it might be time to invest in a new one.

[LAB3]

I'm going to continue hammering my key switch rant home on this one. Two months after cleaning the contacts down to shiny metal I'm back up to losing 1.5v through the key switch. When I pulled it apart a week ago it was back to all crudded up and making bad contact, granted, I didn't use dielectric grease like I should have. A new replacement switch is sitting at my mailing address, it's raining and I had a long ride this weekend anyhow.

[DEEBS11]

Hi LAB3, I have modified most of my bikes with a simple relay that carries the heavy current away from the key switch. A much better way to handle the electrical current needs of a motorcycle. A waterproof relay can handle the electrical system better than an early 1980's ignition switch as shown in this diagram.

[LAB3]

Easy enough to get and put in, thanks for the reminder!

[bikerphil]

The XJ's cranking circuit is a bit more complex than the XS's, some of it goes thru the instrument cluster, such as the headlight kill feature that enables when the starter button is pushed to save power while cranking. If you have a spare cluster, you could try swapping it out. It's a primitive computer, it may have a malfunction.

Not to mention the two interlock relays.

Ok, after further review of the wiring diagram, the headlight circuit runs thru the starter button switch so when the button is pressed, it opens the circuit, circuit is closed when button is not pressed. The cranking circuit has nothing to do with the instrument cluster, neither does the power to the coils.

[DiverRay]

With Phils comment, I would check the wires for coil power. It could be the power from the light circuit and coil somehow got mixed up, or one is bad and it runs when they are both "hot". As I DO NOT know the XJ, this is just a guess.

[bikerphil]

Hey XJkid, does your bike still have the safety interlock relays on it? One of them may be the culprit, such as the clutch switch relay.

Does the bike have the same condition when starting in neutral as it would in gear with the clutch handle pulled in?

[XJkid]

I have jumped the sidestand interlock, the kill switch and disconnected the clutch switch in the headlight. I have been riding like that for months. This is a new development.
The condition is the same in gear or not. I am leaning towards DiverRay's explanation.

[bikerphil]

Couple of things I would try are....

1. Disable the headlight circuit by removing the fuse and see if the problem persists.
2. Check for voltage at the coils, see if it disappears when the starter is cranking. If it has voltage when cranking, check for spark down at the spark plugs.

Do you have a spare 10M TCI you could swap out? Maybe something internal gone haywire.

[XJkid]

Well, I figured it out. It was just dirty/corroded connectors. I followed the R/W wire from the disabled kill switch down to where it joins others at a connector and cleaned that connector. I also cleaned the connectors at the coils. I thought I had cleaned all my connectors in the past, but I missed a few. They weren't cruddy, just oxidized enough to slow the flow. I followed advice proffered here and was successful! I was reading 13.1 at the battery, but only 11.3 on the R/W at the TCI. I understand the TCI requires a minimum of 11 to operate, so I cleaned connectors there, too. I also took apart the starter switch and went at the contacts with a Scotch pad instead of sandpaper so I wouldn't take off too much contact material. I had cleaned it before with sandpaper and was dubious about it doing any good, but it did. All of this got me to 12.5 at the TCI and it fires up great!

[bikerphil]

That's awesome news, corrosion was the cause of the gremlins, way to go!