Voltage Drop at TCI. Weak spark / No Spark

My umpteenth time trying to create this thread as it keeps getting marked as "Spam" .......


Got a 1981 XJ550. Getting voltage drop at the TCI, red/white and black read 11V when ignition is on but drop to 5V when cranking.
I recently cleaned all the connections on the bike and re-did the grounds. Still getting voltage drop. Following a "How-to-ignition-troubleshooting" guide from XJBikes but I cant link it due to anti-spam rules.

We were barely able to get it started with starting fluid, but it does run, just not consistently. Seems like it has a better spark when I'm letting off the start button than when it's pressed in... I <3 weird electrical problems.

 

What is the resting voltage at the battery posts?
What does it drop to when you thumb the starter?
As per our earlier conversation, I strongly suspect that your battery is at fault.

It should also be mentioned that the PO of his bike replaced the fuses with breakers (bad practice imho).
I'd like to know the current rating of the breakers, and confirm that they are not the cause of the voltage drop should the battery check out.

 

I'll try to get that info and other specs about the bike a bit later today. Previous Owner was a Harley Davidson guy and "Japanese parts just fail so I replaced em!" complete with cut wires, improper crimp connections, and a john deer riding lawnmower starter solenoid, etc. I've been going through and re-soldered the harness going into the fuse box area which is now the "Circuit breaker box" area. Just little like 10AMP auto-resetting circuit breakers you pick up at autozone.
http://www.autozone.com/electrical-and-lighting/circuit-breaker/duralast-circuit-breaker/465592_0_0 Like these, but not necessarily this exact one.

I picked it up for $250 as a "complete" bike with clear title. Craiglist deal that was "Too good" to pass up... and yeah... haha.

 

That's the right price range to get something that "looks" complete but probably needs to be gone through. You may end up spending 6-7 hundred to make it right. I spent 900 and then rode mine a ton!

 

Triple facepalm. Is it too late to track this fellow down and rough him up a bit?

 

Already spent about $600-$700 on parts. New shocks, seat, 2 gas tanks (One was bad, got refunded) rear bar, rear box, rear seat straps, new coils, new battery, new levers, mirrors, passenger pegs, exhaust pipes, couple relays and solenoids, pod air filters (Airbox is unobtainium for the xj550 apparently) new handlebars, side covers.. i think that's it. lol

I ain't even worried bout it haha. Guy had it sitting in his storage and at the time I was buying and rebuilding multiple bikes with a friend as a side business. Friend backed out so it sat and sat before I really dug into it to see how bad it was. Had the $ at the time but if I could go back I might've passed haha. I'm sure it'll be a good bike once I can get it running consistently.

 

It'll be a good bike for sure once you're done. I know there are a ton of things I could replace with nicer parts, but choices we all make.

 

PO has no idea how many Japanese parts are on his Harley. Shocks and forks are by Showa (same as our bikes) for the past 30 years, the electrical components since about 1996, Keihin carbs, and a whole bunch more.

 

You need to look in the right places. http://www.ebay.com/sch/i.html?_vxp...550+airbox.TRS0&_nkw=xj550+airbox&_sacat=6000
The 550 Seca airboxes can be a bit more difficult to find (not sure which model of 550 you have), but there are members here who can help. Put a want ad in the For Sale /Swap section.

 

So during cranking the battery voltage drop from 13V to 9.8-10 volts. :/ The bike does bump start like any other bike, just found that out. Hadn't had the new tank ready for gas yet but it started right up without starter fluid while bump starting ssooooo... hahaha man I might just throw it up as a running project bike (Bump start only) and hope someone who has a passion for these bikes picks it up.

Still gonna do some work to it this week: new fork seals, front and rear brake inspection/repairs, and some polishing etc. I would ideally like to get it starting on its own power, but the headache might be too much seeing as I've got multiple projects still to clear out of my life after this is gone.

Thank yall for helping me though,I'll still tinker with the electric ignition as long as I still have it.

 

You found the problem. Look no further. You need a new battery, that one is done for.

It would also be a good idea to pull the starter and inspect the brushes. Replace them if they are near the wear markers. Generally cleaning and re-greasing the planetary gears is also worth doing. This is more of a preventative measure than anything.

 

Also check the resistance for the alternator stator and rotor, pull the cover and check the length of the rotor brushes:

http://www.xjbikes.com/forums/threads/the-ultimate-relay-switch-sensor-and-diodes-guide.27543/

 

^ and clean the rotor traces with an eraser.

 

https://drive.google.com/open?id=0Bxg0hcM5PVnFV0VyeU1ZaElrNFdCcGY3VnBBVnRLdENEQnpF

Ignore the meter, it was in AC volts, not DC. I'll try and tackle the starter motor this weekend or week. But it's proof that it does run and has no problems maintaining spark, just getting that initial spark using the starter motor is our problem. I'll try it with a different battery and see if that has an effect.

 

Have you re-verified that low number at the TCI when cranking? Any more than a couple of volts delta between battery voltage and voltage at the TCI should raise a red flag.

 

We covered that bit in a conversation, but I'm not sure if he's checked the wiring to the TCI yet.

 

Just a thought and may not apply, but there is a difference in checking the battery voltage at the battery terminals vs. checking at the connecting cables. The high current of the starter could be exposing a poor connection at the battery terminal to cable, or at the engine ground.

I know the OP mentioned cleaning connectors and grounds, but if he is still getting that low voltage at the TCI there is a poor connection somewhere if the battery voltage is close to 10V during cranking.

If not in the battery / cabling high power side, then perhaps the ignition circuit itself although that would likely still occur even with a bump start.