Ignition trouble, unusual test results.

I'm trying to resurrect an old bike that I bought for $1.00 from a co-worker. I've got it to the point where it runs, poorly. Headers 2 and 3 aren't nearly as hot as 1 and 4. All for plugs show spark when pulled out and grounded. Installed new plugs anyway since I didn't know the age of the other ones, but that changes nothing. 2 and 3 still aren't hot, so I now begin testing the coils.

Ignition coils:
#1 (1 & 4): Secondary - 11k ohms.
Primary 1.95 ohms.
#2 (2 & 3): Secondary - 11k ohms.
Primary 1.95 ohms.
Caps: all 4 read 4.4k ohms.

Pickup coils:
#1 (1 & 4): 628 ohms.
#2 (2 & 3): infinity/open.

Seems pretty conclusive. However, remember I said earlier that plugs 2 & 3 DO show spark. How could this be seeing that #2 pickup is dead?

I also found it odd that the ignition coils looked good all around except for the primaries. I would've expected resistance to go up instead of down (based strictly on intuition, NOT experience). The plan is to replace them, but obviously the pickup coils are top priority.

Is it normal that the bike will run in it's current state?

I'm on a very tight (read: pretty much non-existent) budget for this project, but if anybody has a spare set of pickup coils they'd let go cheap I'm interested.

And just an observation -- this is by far the most helpful bunch of people to ever grace a forum of any kind. XJ owners are blessed to have this site.

 

have you rebuilt the carbs? could be you have low fuel flow into 2 &3 cylinders.
have you replaced the spark plugs or swapted them from 2 &3 to 1 &2 to eliminate them as a problem?

pick up coils not firing tci for plugs 2 &3 looks like that is the problem. pick ups could be firing intermittently firing
bike can run on 2 or 3 cylinders.
you can splice a single pickup coil into the setup
resistance drops as windings short out

XJ650 models:
Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 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:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
Spark plugs:
0 ohms per plug

 

Yes. I forgot to mention that, and that I am getting some fuel dripping out of the exhaust, presumably from 2 & 3.

Yes, and I also swapped the coils input connectors, and swapped plug wire 1 with 2, and swapped plug wire 3 with 4 and had the same result. Plugs 1 & 4 were running off of the coil for 2 & 3, proving that the condition exists no matter which ignition coil is generating the spark.

Great. Now if I can find at least one....

That makes sense now that I think about it. There's no way the individual wraps could become MORE isolated over time, but I could comprehend the opposite happening.

Thanks for your input.

 

Your coils have removable caps on the plugs ...unscrew them snip off about a 1/4" retread onto wire try to see if this cures it. If you still suspect coils. 80-83 Honda CB750 Coils can be used as these have replaceable wires , Cycle Recycle part 2 has new ones for 39.00 ea and they sell plug wires and NGK plug caps as well. I'm running
these on my 82 XJ750 Seca they mount like stock just swap terminals off old coil to new ones. Or buy used off of eBay .Good luck

 

revisit the carbs.