Maxim gauges

[TopCatGr58]

Hey there AJVOT,

Well, with backfiring, and not starting, could be electrical. ARE YOUR SURE YOU'RE GETTING FUEL? Very lean/starved could cause it not to be able to start. Are these exhaust backfires now or carb farts?!

Pull and clean TCI connectors, and reattach. Also recheck your battery....recharge it. Check fuses, check kill switch, there are many safety relays/switches that can contribute to cutting out the ignition system, clutch, kickstand, to name a few!

Mainly back to basics, fuel, air, fire=ignition. Good luck!
T.C.

[ajvot]

I'm almost positive it's not electrical. I don't lose power on the gauges. I just got back in from the garage tonight. The bike started right up and went into a nice idle after about a minute with the choke on. Seems like it will idle forever with no problems. Revs nice and easy when the throttle is turned. Still no tach to go by, so I have no idea of the rpm's.
Made three trips back and forth down the alley. No problems. Took it around the block once with no problems and it seems to really be smoothing out nicely. Made a second trip around the block, then bang, and no engine. Pulled out my meter right away to check the coils. I measured 25.3Ohms on both coils. I believe that means they are good. The bike started up once and ran for a couple of seconds, then it died and wouldn't start again.
I think it's either heat related, or fuel related. Could I be running the bowls dry? They are all dead on 25mm, which seems to give me good measurements using tubing as a level when the carbs are installed.
Sorry for the long-winded post, I'm trying to give all the details. I'm absolutely stumped!

[ajvot]

Here's a little more info. The backfire is coming from the tail pipes, both of them I think. I have bypassed the side stand switch and checked the tip over switch. I replaced the clutch/starter switch too. Battery shows 12+ volts and is charged.
I have eliminated the octopus by running a single line from each petcock (rear outlet) directly into the appropriate bank of carbs. The other outlet is capped off for now. It only works on Prime/Res. I will be replumbing this once I have it running properly.
It's supposed to be 78 and sunny this weekend. Man I want to ride.

[TopCatGr58]

AJVOT,

For it to run nicely one second, and then bang, nothing, that's almost definitely electrical. Gauges working doesn't mean much! Heat related can cause resistors to separate when hot enough cutting out power. The XJ doesn't have ballast resistor. You checked the secondary side of the coils, but not the primary side? They are two separate circuits joined by a magnetic field! Also, the solder joints on the TCI may be poor, and separate once they heat up? Also try flipping the kill switch a few times and try to restart, corrosion can be fickle! Check the fuses!

The backfires from the pipes shows you're probably getting fuel, but when the sparks are not coming regularly, fuel gets passed into the exhaust, then when the coils and ignition kicks back in, due to the waste spark, the exhaust valve is open when the spark fires, igniting the fuel that's in the exhaust all the way thru from the combustion chamber...backfire!
T.C.

[chevy45412001]

fuses

i'm didn't read all the replys here so bare with me. If you arte still running glass type fuses,please by all means switch over to the newer style. You'll love yourself. Second if you do have the glass fuse change all of them now! I had a very similar prob,it turned out being the fuse. You could not see the break because it was in the end of the fuse were the metal cap was. And it was broke just enough to work sometimes and then like majic boom bike would shut down. It took me days to find that prob. The xj for the most part is very reliable cept for those pestcy glass fuses of yesturyear.

[superdave]

my best friend is a mechanic for 25 years, calls seafoam "tune up in a can". and laughs ! but I have a xj and had electrical probs and found that the, tention on the fuses were loose and when I removed the fuses to clean them the clip ends fell appart and had to replace all the ends. After aa that she was back ! all worked !

[ajvot]

Thanks to Jerry for the replacement gauges. It cured the tach, warning light issue. They must have been fried.
I replaced the fuse block with a new one a couple of weeks ago. I wish I would have installed the new type block, but I still have to use the glass fuses. I did replace all of them last night. I also took the carbs off several hundred times while listening to the US Grand Prix (what a joke this year) to get them dialed in just right. They ended up at about 23.5mm. This gives me about 3.5mm below the bowl, which should be perfect. I still have to get everything sinced, but I used the bread tie method and I think I'm pretty darned close already.
I'm going for a couple of short test rides tonight to see if the problem has been corrected. I'll keep you posted. Thanks for all the great info, and parts.

p.s. I made the synch tool for the YIKES! system. I followed the instructions to a tee, but found one flaw. The fuel line needs to be a little less than the stated dimension, or it will stick in the head after you have warmed it up. Luckily I got is out after using some choice words and a little finesse. I'll try it again with smaller tubing installed.

[ajvot]

Ok, here's the newest info. Still need to synch the carbs, but that's a minor detail. It runs good until you put it under load for about a mile, then goes dead. I have replaced all of the glass fuses with new ones, in a new fuse block.
Please don't think I'm ignoring some of your tips, but I tend to ramble when I write. My electrical skills are not very good, but I have been able to check most things by researching posts on here. Thanks to all of you for this site and you help.

If I unplug the tip-over switch, will that cause the bike not to start or does it close the circuit when it is activated?

The clutch switch is brand new.

The side stand switch has been jumped.

The coils meter out good when hot or cold. Primary and secondary.

The spark plugs are the proper part number.

Battey is new and fully charged.

Charging system is giving 14.3V at appx. 2200rpm

The idle is a little rough, carbs not synched yet.


I'm at a total loss on what to check next. I really could use some tips. Thanks

[shutchis]

Just a guess...

Disconnect the tachometer wiring; it's possible its shorting out the ignition circuit. I looked a wiring diagram for the XJ1100J. You stated the tach wasn't working. Hmm, the tach's circuits are probably "warming up" after several miles, causing the voltage to the coils to go low.

Here's one way the check this out, there are others but try this one. With a digital voltmeter, measure the DC voltage at the coil, the r/w wire to ground. It should be close to battery voltage, approx. 12vdc, or if the bike is running, 12.8-13.5 vdc.

Take the bike for a ride, until it "dies". Measure the coil voltage again. It should be the same as before. It it's lower, say around 8vdc, then I think you're close to finding the problem.

You could also disconnect the r/w wires at the coils and connect them directly to Battery+. This is one sure way to verify the ignition system, assuming the TCI circuit is working.

By the way, did you pull a spark plug wire and see if you had spark after it died?

I love a challenge. Keep us posted. Stan

Oh, you might start by disconnecting the tach.; it's NOT working anyway.

[shutchis]

Good idea...disconnect the tip-over switch; Just un-plug it. On my XJ, the MC stopped running one day...no spark. Traced it to the tip-over switch. I unplugged it and left it in the holder. Fixed the problem.

[ajvot]

Ok, here's the deal. I was ready to have an XJ bonfire, when I found some really hot wiring. I had the bike running for about ten minutes and was shaking, pulling, and banging on the wiring harness, connectors, and relays, etc. I Grabbed ahold of the connector that goes to the alternator, I think, and it was hotter than hell and had some melting taking place. This is the same connector that this had happened to originally.
I'm getting ready to go out, before it reaches a 100 degrees in the garage, and see if I can trace this circuit out and figure out why this is happening. I have replaced the reg/rect, alternator, etc. The connections were scrubbed with contact cleaner and a gun cleaning brush, then greased. I'm at a loss as to how this can happen. Any tips on what to look for?

[Ken Talbot]

Look for a corroded main ground connection where the battery cable attaches to the frame. While you're at it, make sure there is bare metal to bare metal contact - no painted surfaces. I've seen some very interesting effects like long arcs jumping from that screw head to the frame!!

[ajvot]

I checked the ground strap again. I made sure it's grounded by lightly grinding down the frame side and sanding the strap. I'm concerned that if I keep it running until it dies again, that I'll fry the TCI, reg/rect, or alternator because of something silly that I'm missing.

Here's a couple of questions:

1. If I have a coil that is going bad once the engine is warmed up, will the resistance still measure the same?

2. I'm a little confused about how to check a coil for sure. I have just been measuring the resistance from plug cap to plug cap, and from the primary wire to the other primary wire. Am I missing something here?

3. If I have a coil that is heating up, then shorting out, could this be the problem? I'm by no means an electrical guru and the manual is a little vague and confusing on some of this.

If anyone has a set of bonifide "good" coils, I might be interested if this might solve my electrical nightmare.

Thanks for everyone's patience with me and this thread.

[TopCatGr58]

Hey AJVOT,

Ken's talking about the battery terminal ground cable, but you should also check the main engine to Frame grounding strap that's at the rear of the engine!

IF your coils are going bad/shorting out when getting hot, you're not going to FRY your TCI! Your checking them essentially correct, and if you're getting proper resistance readings thru the cap to cap, then you don't necessarily need to pull the plug caps off the wires. The coils without the caps will measure around 15K, plug caps can be between 5k-8k, so can add 10 to 16k ohms to the total. If they are breaking continuity when they heat up, then you should read INFINITE RESISTANCE when tested. If they are "shorting" out internally...bypassing windings, then you should have much lower resistances than cool!

Sorry I don't have a spare set of coils to loan/give to you!?

[Ken Talbot]

When you were cleaning your connectors, how did you get down inside the female end?


The male ends:
are easier to get to, but both parts need to be clean for a good connection. Sometimes, you need to pop the individual plugs out of the connector block to really get them clean: