Serious backfire

to test side stand just pull the side stand relay it will over ride side stand function

 

Sorry it took so long to respond .... was on elk hunt. (don't ask)

Battery initial at 13.2 v and after crank @ 11.7 v.

 

k-moe - did battery values help w/ diagnosis?

 

with bike cranking and meter attached to battery what does the voltage drop to if under 9.8 volts bike wont start

 

as i recall it didnt drop below that value. I believe that is what you asked.

 

Well - either start replacing electrical components willy/nilly until I stumble onto solution or haul it to an old bike expert.

 

Before willy nilly go through EVERY connection (under tank, under side covers, inside headlight bucket, inside handle bar controls, etc) and clean, die-electric grease and reseat/ tighten.

Pencil eraser, small jewelers file, emery cloth for cleaning off any corrosion.

 

what was your total electrical failure?

Start with the basics and ohm out your entire ignition system. could be you are not firing on all plugs.
have you looked at the spark plugs?

did you clean out the enrichment circuit and pilot jets on your carbs as suggested.
could be the wells in the bowls are clogged preventing the enrichment circuit from working to all carbs

 

Okay, here is what I have continuing. (XJ750K) Continues to have electrical failure when cold but always (until now) restarts quickly. This time no restart. All lights and functional light indicators illuminate except neutral light. No starter turnover.
Packed it up and got her home, within a few (<5 minutes) all functional and will start. So, with battery only 1.5 years old and last checked it was charging within specs I'm suspecting the Regulator/Rectifier.
Will a bad rectifier act in a intermittent way or when they go bad will they just not function?
I'm trying to diagnose electrical issue without taking it to a shop. Any additional help appreciated.

 

if bike thinks it is in gear it will not turn over except if you squeeze the clutch and the clutch switch is working properly.

 

Bike was in neutral and clutch operated frequently. Is there a way for it to believe its not in neutral yet it is ?

 

bad neutral switch or the wiring going to switch may have issues, loose connection , corroded connectors.
if light does not come on could just be bulb.
clutch switch opperation should overide the neutral switch.
could also be an issue with the starter safety relay.

check neutral switch for ground connection with meter.
check clutch switch operation by disconnecting switch and putting sa jumper across it.
check the bulb I do not think it needs to work for operation but it is needed to indicate switch works and is easier to get to than switch and its harness

 

Thanks, I will check neutral switch. The neutral switch light once again illuminates after she rested for a few hours. Again, all lights functional except neutral light during failure.

 

Oooh! I saw this before!
On a Yamaha big bear, the neutral switch safety in that particular year was controlled thru the cdi unit, not seperate relay, something was effed up, same symptom, if you left the key on while waiting you could watch the light slowly get brighter over an hour or so, when lit, cranked again.
Changed CDI, mint.
Ironically, i tried the CDI on another big bear that used a seperate relay, not thru the box, it ran fine.
Yor bike i believe has seperate safety relay, this is likley the culprit. Id change that first

 

Have you tried to hold the clutch in and then bypass the starter button by jumping the starter solenoid? I would go back to the basics of fuel and spark. If you pull a plug, keep it in the spark plug boot and lay it next to the head. Turn key on, pull in the clutch and then short the starter solenoid. Hoping this will crank the engine and you will see spark. It the bike cranks and you see spark, Trouble shoot from the starter button to the solenoid.

 

I didn't read through the whole thread, but skimming this sounds kinda like what I went through on my Son's bike....all issues were traced back to the tci.

https://www.xjbikes.com/forums/threads/ugggg-xj550-shutting-off.115984/

https://www.xjbikes.com/forums/threads/boom.115586/#post-576834

 

Okay - back again. Last Fall ran like top, put away for 2 weeks, next attempt to start it would not. Plenty of battery and kept on trickle charge over winter. Try again in Spring and would once again not start. Turns overt just fine .... hoping Gremlins would fix over winter.
No spark as I firs try to diagnose. I'm working through Yamaha Haynes trouble shooting. Ignition coil would appear not to be an issue as both sides have no spark, seems unlikely both would fail at same time. Spark plugs all new. Fuse solid. Battery at start 12.7 v. Besides checking ALL connections, this seems to leave me with Pick-up coil and TCI / (voltage regulator). I would try to electrically test but I'm clueless and suck at electricity checks.
Any other ideas or encouragement?

 

first go to tci and disconnect the black wire with white stripe try to start bike.
if no start

unplug the connector from the tci that goes to pickup coils gray orange and black wires plus a black and white wire

ohm the black wire to orange then black wire to gray wire. also ohm black wire to ground should get no reading for black to ground

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