Tachometer On 1982 XJ650 is working when bike is not running

1982 Yamaha xj650 maxim

The tachometer on this bike when I turn the key on does...nothing like normal then after about 5-7 seconds it starts going nuts and I can hear something clicking on the bike I think its the electrical box that controls and reads what my rpms are at ,or its the turn signal relay witch doesn't make sense to me but could be ,wires seem to be in the right spot i cant really tell if their is a short or not. So basically the tacho works when the bike isn't even running just the key on i don't know what it could be. also the horn used to work and now it makes a quick squeak but nothing after while holding the button.

PLEASE SHED WISDOM ON ME


Please help me this is really making me regret buying this motorcycle

 

Does the bike run? The sidestand relay will cause the tach to jump a round when it "clicks" on/off. Sounds like you have an intermittent connection there. Places to look would be the run/stop switch, sidestand switch, and clutch switch. Make sure connections are good and switch contacts are clean.

With a bike of this age, it really is worth the time to go through all the connections and clean/cycle them to ensure good connection. There's a lot in the headlight and they are usually corroded from moisture over the years.

 

Yes the bike runs and I am in the process of going through to make sure all the wires and connected and where they are supposed to be ,also making sure to take them out and brush them and grease them and put them back in but i have not started that whole process yet but why would that make the Tach move and engage the electrode that makes the tach move are they on the same wire? ALSO PS the actual needle in the tach is moving not just jumping around like its reading 2-3 rpm up to5-6 sometimes

 

The R/W wire out of the Stop/Run switch will connect the 12V positive side to the ignition module, the starter cutoff relay, and the side stand relay. When 12 volts are applied/removed from the ignition module it is normal for the tach to jump a bit since it gets it's signal from one of the coil outputs on the ignition module. I'm pretty good with electronics but I don't get into circuitry enough to be able to explain exactly why the tach jumps. @Rooster53 might be able to. Not sure what you mean by " and engage the electrode" unless you are referring to relay coil.

If it is more than just jumping around I would suspect the tach is bad. The tach is 100% self contained and relies on a signal from the ground side of one coil, if the bike is running normally but the tach is acting up I would suspect the tach. Good thing is they are very common and easily found.

 

First of all thank you ,your awesome and here's what I found out. The clutch switch is broken like I don't know how I didn't see it but that's broken so that's gone(ordered new one), next I jumped that connection so I had control over the circuit and tried to recreate it moving around like that and I could not , I'm currently going through the whole wire clump in the headlight just unplugging and sand / grease then and put them back in the same spot if they were correct so I don't know anything else right now but that, also weird question are the front two blinkers supposed to be steady on when the key is on and running?

PS the tach is fine I also found out a fuse connection is broken so when i hold it and make a good connection the cluster lights up and everything works ,still in trouble shooting stage im just overwhelmed but i have set things i know are wrong so maybe its just those two things in combination making it go crazy

PPS i dont know how the tach actually works the "electrode" to me is what ever give the tach the signal for it to say your at whatever rpm the engine is at

 

That will simulate the clutch being pulled in, fine for testing but be aware you could start in gear if the sidestand is up.

No that is not normal for a stock 82 Maxim 650. Some people have swapped out the front blinkers for combo blinker/running lights, hard to say what the PO did but it could also be a wiring issue.

One thing at a time.

The tach is self contained, it relies on one of the coil "signal" wires from the TCI. This is the same wire that makes the coil spark, if it runs and you have spark then it should work as there are no other components to make the tach work. There isn't a sensor on the engine like you'd expect with an oil pressure gauge etc.

 

Thank you jayrodoh for all this info

So I a couple things I fixed today first was sanding everything that could be sanded and greased everything that could be greased and put the battery back in and everything worked great for some moments some not to great, then thought I'm a idiot and didn't check the ground cable from the battery took it off cleaned and it and everything worked the way it was supposed to. Also before fixing the ground I had to fix my fuse box the metal connectors were broken so soldered new fuses to wires(for now ) and everything worked amazingly.

Two key things happened the starter actually moved it had moved before to start the bike when I bought it and once after at my house but I could not get it to go after those two ,I think it was a combo problem from the ground not being good and the fuses not being a good connection. Then when I was trying to start it the rpm gauge was actually reading it properly at 2500 rpm and I think that was also a fuse issue because of your insight you gave me yesterday , also the bike isn't able to run currently have the carbs out they were SO GUNKED UP idk how it even ran but everything is nice and clean now and just waiting until tomorrow when I get my carb kit.

The front two blinkers always being on are therefore aftermarket and it doesn't bother me easier for people to see me and the directional part actually work so no sweat but thank you for telling me that they are not stock Ireally thought they were.

One last thing I did test the kick stand switch yesterday and that was good so I knew it was not that. Thank you I will update this post when I get her all going

 

Back Here tonight with bad news about electrical, my bike refuses to move the starter at all I cant get it to move it no matter what I do EVEN JUMPING THE LEADS I have no idea why. I took the starter off and its fine NOTHING WRONG I have a new starter solenoid and I have a jumper on it when I even try to start it and nothing happens but in good news the tacho isnt doing the weird moving thing when the bike is not running so I have no clue this bike hates me guys....help thanks