Just another help thread.

Hi all, I have an 82 xj 650. Just started it up for the first time this season and she fired up beautifully. Drove it around all day no issues. The very next day I go to ride it and it has lost all power and acceleration. The bike Can barely get up to 55mph. When throttle is applied the bike sounds like it will die ,sputters and the whole bike starts to shake/vibrate badly. When in neutral the bike revs up to redline just fine with very little hesitation and a little bit of backfire. But other than that it sounds healthy when not in gear. And it behaves the same in every gear. Checked the plugs and they were good, Fresh gas, where do I start.

 

You will likely be asked for some background info. Carbs church of clean clean? Valves in spec? Ignition system (pickup coils, ignition coils, wires, caps) all in spec? Intake boots cracked? Known, tested good battery? Just a few things off the top of my head you may likely be asked by others much more knowledgeable than myself

 

They are church clean, brought to a shop to have ultrasonic cleaning done. Valves are in spec, battery is a new AGM battery. I have not personally checked the coils or the wires. Like I mentioned before the motor runs smoothly and revs good when in neutral but when in gear it runs poorly all of a sudden. I put 93 octane in the tank also. If that makes any difference

 

one simple check ,before you delve into the electrics or carbs , is check the fuel line from the tank to carbs, is delivering full fuel, put fuel tap on prime and check for kinks.
stu

 

check your oil level if your needle vales allowed fuel into the oil hydro lock would give symptoms like that

 

When I checked the oil yesterday it was up the the top marker with a slight gap of air at the top of the sight glass. This is with the bike on its center stand.

 

good n the oil.
check your charging system hook meter to battery bring up to 2000 rpm should get 14.2 volts.
next ohm out the pickup coils you do that at the connector at the tci. looking for 650 ohms
ohm out the ignition coils as well primary 2.5 ohms and secondary. 11k ohms
plug caps 5k
if you measure the secondary with caps on 21k ohms
are all the header pipes getting hot?
look and see if you have a clean air filter could have a mouse in there.
check fuel flow from petcock see if the problem happens when set to prime. you may have a vacuum issue as in petcock not working colappsing vacuum line clogged outlet into fuel line

 

I'll check these things when i get home tonight. As for the petcock, should I run the bike on PRIME , will this cause any damage? Flooding, etc? Is there a write up on ohming coils and where to find these connections and test them? Thanks

 

if your carbs are working properly prime will not cause any problems just switch it back to run when done

 

ignition coils secondary measure from plug wire 1 to 4 and from plug wire 2 to 3
for primary you can measure from the other tci connector with red/white wire if out of spec go to connector under gas tank gray to red/white and orange to redwhite wire
pick up coils are measured from tci other connector gray to black and orange to black

 

Hey see your in Chicago land , I Live over state line in Indiana . One thing you state carbs were cleaned ultrasonically , BUT were all the seals removed and replaced ? if butterfly seals were left in then good chance you have a big vacuum leak . One thing to do pull all the plugs and check the color of electrode and put a fresh set of plugs in and see if this helps. While your at it unthread the plug cap trim off a little of the plug wire and rethread cap back on.

 

Carbs were completely overhauled. New jets, needles, seals, gaskets, o rings, etc. Plugs are new as of last season. I checked them the other day and had no signs of wetness, carbon deposits, or aluminium deposits. Looking for my temp gun so I can check the exhaust headers for temp differences

 

So I measured the ohms between 1 and 4 and my reading was 28.6k
2 and 3 read 21k.

Side note: it was hard for me to get a true reading as the numbers jumped around quite a bit before it settled for a moment. The other circuit stabilized immediately.

 

the spark plug caps unscrew from wires twist off the one with high readings and just measure the wires then the caps alone.
wires may be corroded as suggested above trim them back about 1/4 inch

sounds like the wrong caps on the wires

 

So the spark plug caps for both 1 and 4 are reading 9k~10k ohms each. All the wires and coils were good.

 

that will cut down on your spark po likely just put on what he could get @chacal sells replacement caps at a good price and proper 5k value. you are using non resistor plugs correct?
specs
Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

listed in the electrical section

 

After changing spark plug caps, the problem persisted. So, I took the carbs apart. And to my surprise, the main jets for cylinder 3 and 4 had somehow managed to unthread themselves completely from there seats leaving an unmetered flow of fuel into the ignition chamber, which explains why it would sputter and feel like it was guna die. Put back together now and she's faster than she's ever been, even better than before. I spent about 5 hours cleaning the carbs since I was in there. Much better now. Thanks guys