Probable Solution to the "Firing on One Cylinder" Issue...50MPH at WOT No More!

[ViolinARC ()]

OK, I'm new here and I wanna share some knowledge, which will hopefully help many of you solve this common problem.

I have a '95 XV1100 and for about a year now I've been experiencing what seems to be a very common issue, intermittent dropping of one cylinder, which seems to be misinterpreted as a fuel system or carb problem. I've read many threads where the owner has completely rebuilt the fuel system only to have the problem pop up again so I am joining this forum specifically to share my experience and to hopefully help fellow Virago owners solve this elusive gremlin.

At first it seemed to be a strange intermittent power issue that I, too, related to the fuel system. This felt especially true since I had a significant rusting problem in my fuel tank (I won't go into that right now...heh heh). So, being the procrastinator I am, decided that it was time to pull the tank, etch the rust out, flush the reserve tank and replace some lines and filter. After doing a bang up job (if I do say so myself...LOL), she seemed to be running perfectly and I sighed a sigh of relief believing that I wouldn't have to tackle the carbs.

DAMN...after a couple of clean runs, she started acting up again. Same old symptoms...runs fine and then feels like a one-cylinder slug. WOT and only 50MPH...WTF (starting to sound familiar?!?).  Now I'm bound and determined to get this thing back to normal cause I LOVE my Virago and have owned three to date. I started toying around with the bike in hopes of getting the intermittent problem to reproduce itself consistently. I rocked the bike back and forth, tinkered with cables, checked plugs, fuel lines, etc. trying anything in a desperate attempt to avoid buying new carbs or having to rebuild the old ones.

Finally, when turning the steering head back and forth, the bike sprung to life and then as I turned it back the other way, one cylinder. BINGO, I had stumbled upon something interesting. I then grabbed the wiring harness at the point where the single harness comes up on the left side of the tank and splits into three bundles, pressed my thumb into the harness and ROAR, the bike immediately responded with both cylinders. Release and one cylinder...press and WOW! I found the problem!! So I started cutting open the wiring harness to find that bad boy and as I was going one wire at a time, a red wire w/white stripe pulled loose from one of the upper bundles of wiring. I tracked down the only point in the harness (the upper bundle of the three) where there was a splice and sure enough, as soon as I touched the loose wire to that point (two other red/white stripe wires)...ROAR, both cylinders come to life and stay alive...something new! Remove the wire and BINGO, one cylinder again so I find a point farther down the wire to splice into and VOILA, the bike runs better than when we bought her new!!

I neglected to mention that I had taken the bike in three times after purchase to complain about a persistent backfire when letting off the throttle only to be told that the backfire was common and normal operation on V-twins, which I now know is total horse hockey because the backfiring is completely gone and she hits triple digits like a sports bike!

I hope those of you who are experiencing this issue find my experience to be invaluable in getting your machine back to the place where you can love riding it again...please post your success stories here if it works for you and you finally get a chance to put this persistent problem to rest. Peace and good luck!

UPDATE: Just so everyone knows this isn't a fluke, she's still running strong with not even a hint of backfire!  I even fired her up cold yesterday and started goosing the throttle to force a backfire but she ran clean and strong throughout the test...

Problem SOLVED!!!

[bstig60]

Thanks.............

[rayillu]

I have had the same problem and I checked everything under the sun and nothing so I decided to cut open the harness only to find out it was previously cut open.  The only thing there are no loose wires.  The red and white wires are there spliced together but with a brass ring crimped around them and the ends of the wires sticking out.  There is another join like that an another join like that with green wires only they are sodered.  All the joins were covered with electrical tape.  They were not the neatest joins I have seen.

Is this the factory wiring?  You said you had bought yours new.  Mine is older than yours (1988 xv750) but I imagine it should be similar.  Even though the joins are solid could this be causing my running on one cylinder problem ( ...no spark coming from the front cylinder coil ) ?

What are your thoughts? Thanks.

Ray

[ViolinARC]

Sounds like someone already found that short and did a poor repair.  Personally, I'd correct the old repair and see what happens since you already have the harness opened up as there could still be a short.

On another note, I had a similar issue on an old 750 and there was one wire that looked perfectly intact until you bent the wire slightly, which was causing the same single cylinder issue.  After cutting into that wire, I discovered that the insulation was perfect but the wire inside was "green" and corroded.  I cut out the bad part of the wire and spliced it for another successful repair of the same issue.  It took two trips to the shop and then my decision to finally tackle it on my own.  It took me about 8-hours of chasing wires but I did find the problem and it was definitely a short as it was with the 1100.  The 750 ran so well after I fixed it that I was able to sell her for more than I paid after two years of riding (not enough power for me)...

Keep me posted as I'm willing to bet there is still a short in the wiring harness somewhere...keep looking and GL!  Peace...

[rayillu]

thanks very much.  Much appreciated.

[rayillu]

Hey, thks again.  Thought I would follow up on my solution.  I did find another questionable harness repair.  It was still connected but not very good so I re-did it.  But what it ended up being was a bad TCI.  Got the contact information for the guy in Illinois who rebuilds them and sent mine out.  Once I got it back from him and installed it....... bingo.  Runs UNBELIEVEABLE.  The best ever.

Ray

[flatdog]

Hi Guys,
I just inherited an '85 Virago ( virago n. , pl. , -goes , or -gos . A woman regarded as noisy, scolding, or domineering. A large, strong, courageous woman.) that has the misfire on the front cylinder and am going to clean and rebuild carbs and look for the wiring problem solved here. I come from an Experimental Aircraft background and would like to share a fix for fuel tank interior rusting and debris problems common on older metal tanks. I live in Florida, the humidity capital of the world, and the water and crap in the fuel in everything here causes problems. In metal tanks (works in plastic, fiberglass, too),  I clean, derust by adding small gravel and water to dislodge the rust particles, remove the gravel, dry by using compressed air, and rinse with acetone, then use "Randolph Alcohol Resistant Sloshing Sealer" in the tank, allow to harden for several days. Then your tank will be squeaky clean inside with a protective coating that will prevent rust and corrosion. Be SURE to use an inline fuel filter, as you know, all fuel is contaminated with all kinds of crap that will clog fuel lines and carbs. This sloshing sealer is available from Wicks Aircraft Supply and Aircraft Spruce Supply. Hope this helps..And thanks for all posts that help newbies like me to diagnose and fix problems we all experience.