Hey everyone, I was given a 1982 XJ650 that needed some minor work before it can run. The problem I'm facing now that I can't figure out is this:

The neutral light will not light unless the clutch is depressed, making it so that the clutch must be depressed to start the bike (which runs otherwise). I was given a 'diode' by someone who had done some work on the bike and was told that when I put the diode in, it should resolve the issue.

The diode I was given is a small black box with 2 prongs perpendicular to eachother forming a sort of offset 'T'. If anyone knows where this goes, or how I can resolve the issue otherwise, please let me know! This bike is so close to being ride-able!

Thanks

Isn't that a safety feature on some bikes, requiring both?

That makes me think I have an issue, actually, that I've been meaning to ask about. When I have the bike in gear, but start with the clutch held in, it will start--but it will yank the bike forward like the clutch is still engaged until it is running, and then it will sit still. Luckily my bike starts up on the first or second kick, so it only goes forward a bit, but what's that all about? Doesn't make any sense to me, since the clutch is supposed to be a completely mechanical assembly... What difference could the bike starting vs. the bike running make on it?

Anyways, somehow putting the bike in neutral sends a signal and you must have a bad diode that is preventing that signal from being sent or received (I'd bet received). The clutch bypasses that, luckily.

So it's supposed to do that? Haha that's not what the repair guy told me, but if it will run and get into gear normally like that then I'm OK with it... I'll wait to see what someone else has to say.

nope not supposed to do that. sounds like your neutral sensor is unhooked or bad. not sure what they were thinking with the "diode" which doesn't sound like it looks right to be your average diode.

Looking at the wiring diagram it looks like the ground on your neutral switch is bad, or the switch itself is bad, so the power is finding ground through the clutch switch when the clutch is depressed. There IS a diode wired between the neutral switch and the clutch switch to prevent this from happening, and it sounds like this diode on your bike is burned, but the root of the problem is probably (hopefully) just a dirty ground at the neutral switch. Clean it's contacts up and ring it out with a multimeter to verify.

-The bike has a safety circuit that:

Allows it to start in gear IF the clutch is pulled in AND the sidestand is up.

DOES NOT allow the motor to "spin" if the sidestand is down, regardless of clutch position, unless the bike is in NEUTRAL.

-The safety circuit consists of the sidestand switch, neutral switch, clutch switch, sidestand relay (some models) and the safety (cutoff) relay. The "diode block" plugs in inside the shell, and contains diodes belonging to more than one "unrelated" circuit, including as mentioned above.

So if it's a bad diode, is it one like this that I need to replace it with?

www.ebay.com/itm/YAMAH..._500wt_716

Thanks!

that would be the block the diode is in if its bad. they can be repaired as well if you are handy at that sort of thing.

here is what it looks like inside (with a broken diode on the neutral switch system)

Now I just have to find the grounds you said to clean and try that!

As posted earlier, and sage advice...

"but the root of the problem is probably (hopefully) just a dirty ground at the neutral switch. Clean it's contacts up and ring it out with a multimeter to verify."

the neutral sensor is mounted in the bottom of your oil pan, left side (when seated on the bike) about 3/4 of the way to the front of the oil pan just inside the frame rail. it is up in a recess and only has a single wire running to it. If you can't find it I will take some pics for you tomorrow. My 750 had a bad diode that I repaired (see pic above), then I found out it also had a bad sensor and after I replaced the sensor the wire that runs to it broke.

On the xj9 that sensor is very hard to get at. Fortunately good old Chacal supplies a special flexible socket that allows you to get in there and of course the sensor itself.

it is on all of them you either need the special tool, loosen the motor mounts and apply judicial force to separate the frame and motor a bit, or grind the edge off of a socket so it will fit up in there. they engineered the gap about a mm to small as the next size down socket will slide right in there but the right one just wont fit. that's only if you have to remove the sensor though hopefully it is just the connection or the wire that is the problem as those can be done without removing the sensor.

With Chacal's s tool I didn't need to unbolt the motor

ya thats only if you don't have the special tool or a spare socket to cut up.