1983 XJ750 Midnight Maxim

I’m seeing a theme where bikes are ok for a couple of weeks after buying them then things go wrong . Well I just bought mine 3 weeks ago everything was perfectly fine until it stopped firing. Checked battery, Has gas, Kill switch, using choke, stand is up. Have checked plug wires for spark and am not getting one more times than not. Mechanic says he wants to replace the pick up and plug wires ... what are the chances that the pick up is what the problem is?

 

Close to none.
Did the mechanic test the pickup coils, or is he just making a guess?

The most common cause for suddenly not having spark is a sticky kickstand switch.
Peel the boot back and clean it with contact cleaner while moving the plunger, then follow up with a dry-film lubricant.

Used machines (all of them, not just motorcycles) all need going through, even when they can be ridden away from the sale.

 

Pretty sure he’s just guessing but he hasn’t had that long to look at it. It’ll fire at random times and some days it’ll fire and start up all day long. Kick stand switch isn’t it he’s already looked at that.

 

bike has problems a few weeks after buying. that why the PO sold it


The Ultimate Relay, Switch, Sensor, and Diodes Guide this link has the specs for ignition system

remove the side stand relay
- on all 1982-84 XJ750 Maxim/Midnight Maxim models: under the left frame side cover, on the plastic regulator-rectifier mounting plate.
this will eliminate the sidestand as the problem. removing the relay deactivates the side stand switch function.

if removing relay does not solve problem
Disconnect the Black/white wire at the tci there is a connector about 3 inches from tci. this wire is what shuts down the tci with side stand


here are the specs on your ignition system
XJ750 air-cooled models:
Pick-up coils:
650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
Ignition Coils:
Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range
Spark plug caps:
1981-83 models: 5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
1984 RL models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

ohm out the system then ohm out the pickups when the bike stops firing.

do you still have glass fuses? replace the ignition fuse with a new one or
if so replace the ignition fuse with an inline fuse holder or replace the whole setup.

ebay sells the stock style set up

Your Fuse Box -- A Ticking Bomb??? By: Rick Massey


clean the connectors in the ignition system

when you do not have spark chase the voltage to the tci

check voltage at fuse both sides at the crimp then at the tci red/white wire

 

But have YOU looked at it? Have YOU actually TRIED pulling it out the rest of the way after putting the side stand up? Have you tried bypassing it? That's how to troubleshoot that one.

The second thing to check is your battery voltage and voltage drop when you try to start the bike. I know you said you checked the battery. HOW did you check it, and what were the results?

Did you replace the plugs? Did you pull the caps and trim the wires back a little yet?

Been riding in the rain at all?

Aside...
Next, how long has it been since the carbs have been THOROUGHLY cleaned? Shim clearances checked? Oil level checked?