2 days ago, only 1 cylinder firing, yesterday BOTH, today just 1 again. (SOLVED)

[El Cheapo ()]

i've just got a 1986 yamaha virago 700. It's got spark and compression.. i put in new plugs, and i cleaned out the carbs (perhaps not enough) then reset the mixtures until it was idling.. on only one cylinder. which is how it was before.
yesterday i pulled the plugs out, let them dry, rubbed them with a wire brush, then checked for spark, i had it on both, i cleaned the connections at the coils with electric cleaner and a little file. i checked the igition wire to the plug for the cylinder that wasnt firing.. there was some electric tape on it. i took it off and found a little slice in the outer rubber insulation that looked like it got pinched by the fuel tank. it didnt go deep enough to penetrate the inner layer.. i wrapped more tape around it.  i put everything back to start it. at first only one cyclinder still.. but as i stood there watching it, the other cylinder just magically started working.. first a little white smoke, then it worked, and it sounded wonderful. and i set the idle, and rode it around town. later in the evening i started it again and it was back to one cylinder.
TOday i tried starting it, and only one cylinder works. only the front. i tried everything from yesterday, but no luck.
I've read all the posts about it and it sounds like its either a dirty carb still, the tci unit, the cdi unit, the breather tubes, or the mixture setting.
i think i want to try cleaning out the gas tank, replacing all of the fuel lines and breathers, getting a new fuel filter, cleaning the carbs again and dipping them this time.. and maybe that should do it. the bike has less than 6000 miles on it. there was a lot of gel in the float bowls the first time i cleaned them. i should also mention that there is some heavy backfiring going on.. both out of the exhaust of the cylinder that is not firing, and out of the intake! it blew a hole right through the cardboard air filter at the intake! i feared for my knee! one of the little cover screws fell out! i should mention too that fuel is just dripping out of the exhaust pipe that isnt firing. the lame cylinder plug is completely saturated when i check it. especially today since it would only idle with the choke on.. as opposed to yesterday, where i had both cylinders running, and it was idling so smoothly.. i actually was considering registering the bike asap.  but today, horrible.. yesterday was such a tease. anybody feel like talking about only one cylinder working on viragos anymore?? hah. thanks guys.

[bstig60]

Could be choke closed or pilot jets clogged. You will need to run a soft wire through the pilot tube to clear it out if it is clogged. Soaking will help, with high pressure air, but a small wire is preferable to clean the pilot tube.

[deezee66]

check your compression there have been rear head issues with these motors also i would check the timing chain it may have a stretched timing chain or worn gears

[stingypaperwaffles]

Have you had any luck solving this problem? I am having a very similar problem with my '85 700. Whenever I start it (and I mean WHENEVER, even after a 2 minute stop at a gas station), it seems it is running on only one cylinder. Actually, it will be fine for the first 30 seconds or so, then it will start crapping out. It will have no power whatsoever. After it runs about 5 minutes, whether idling or riding, it will start to smooth out, then it will just take off and run perfect until it is shut off again. And I did notice once that I had a few drips of fuel coming out the exhaust right at the head, only on the front cylinder, while it was warming up one day, which leads me to think I have a misfire problem. (unburned fuel running right through to the exhaust, also backfires out the exhaust real bad during these episodes) I have rebuilt the carbs, and set the float levels and sync'd the carbs previous to this problem. It ran perfect after that, until I washed it. I know my battery isn't great, but it always starts it, and even after putting a charger on it, the bike does the same thing. I checked the resitance in the coils, primary is good, but secondary is at 18k on both of them (I think clymers says 13.2K is spec). I also checked them immediatley after I shut it off when the bike was warm and running good, still the same. I do still need to check the connections to the TCI, may have a problem there because it seems to have started right after the forementioned thorough washing. Anyway, this is real frustrating and any insights or suggestions would be greatly appreciated.

[El Cheapo]

Hi,  I identified the problem my virago 86 700 was having. I narrowed it down to a failed float. The failed float, altough it floats, weighed 2 grams more than the functioning one. I figured out that it was the floats by swapping them. When i swapped them, the other cylinder started working, and the previously failing one was firing.  Maybe you should try that sawp.
My failing cylinder, like yours, also had fuel leaking out of the exhaust. .. a lot.
I havent posted anything as (solved) yet though because i am still waiting for the new float. I was able to find one at boats.net. It's taking two weeks to get here.
It sounds like your coils are probably alright. Especially if they are both the same exact ohms. Maybe you should try testing for spark by removing the plug, reconnecting it, and holding reak close to the engine. (make sure chokes not on, and put a rag over spark plug hole, or you can get sprayed with gas in the face like i did.)
If your sparks not strong enough looking, I think some people put some kind of Accel Harley coils in their bikes to fix that sometimes.. i cant remember the details, but i read about it on VIrago Tech Forum once. you should check that forum out.. they're good.  Goodluck! let me know how it goes.

[ViolinARC ()]

Sounds like you have a short, check this out and see if it solves your problem...

Read here: http://www.nabble.com/Probable-Solution-to-the-%22Firing-on-One-Cylinder%22-Issue...50MPH-at-WOT-No-More!-to24692447.html

[stingypaperwaffles]

Well, I have checked all the wiring, everything checks out fine. The other day, I swapped coils around with some rigging, and the problem moved with the coil. But before I take that plunge ($300 for the OEM for the pair, or $150 aftermarket from Dennis Kirk), I am going to try different plugs. I have brand new NGK's in it, but I have seen all the posts on here about using Autolites with much better results, which goes against everything I learned in auto mechanics. But, worth a try.

[bstig60]

I can tell you from a good amount of experience that the Autolite AP63 Platinum plugs do make a difference in the Virago's.
Since the problem moved with your coils, have you gone through the procedure to check out the coil primary and secondary winding? There is a procedure in the Clymer's Manual for testing them with a Volt/Ohmeter. Another possibility with the older Virago's is the coil wires. They have a resistor in the end of them of about 5000 ohms, sometimes taking it apart and cleaning it inside can help. If your bike has the replaceable wires, then replace the wires with solid copper 8MM automotive wires. If not, try ebay for some used coils. Also, I have a source which might have some coils off an '86 XV700. Try Mark's Cycle Store in Grass Valley, CA. 530-273-8337. If he doesn't have them off the bike he has, he can probably find them for you.

[stingypaperwaffles]

UPDATE: Well, I rode to work yesterday, and the problem was way worse. It ran on the rear cylinder the entire 30 miles, hitting on the front maybe a few licks here and there. Started checking it out during some free time at work, bouncing ideas back and forth with another guy. We checked all the wiring, coils, cdi outputs, everything. We hooked up the other coil to the front cylinder, couldn't get anything. Started it back up, thinking maybe it just couldn't get warmed up that morning, it was a pretty cool ride in, about 60 degrees. Now it had fuel leaking out of the lower front exhaust joint. Very frustrating. Finally checked the vacuum hose to the stupid vacuum operated petcock, and it was full of fuel. So, I am certain that was a major part of my problem. Plugged the line and set it on prime and it ran great all the way home, and back to work today. I still need to do some checking and see if it still misses while it is warming up when I leave today. Being that this is my first Virago, (700), is it pretty normal to be running not so great for the first few minutes? I also noticed going through town today that it was a little rough, lurching and popping. I'm thinking that I may need to re-sync now that I'm not sucking all that extra fuel down one cylinder. Will probably do that Sunday. Does anyone know of a good source for a petcock rebuild kit?

[bstig60]

You need to make sure the petcock isn't leaking. It sounds like it is. If so, it will need a new kit put in it. They are available at www.partsnmore.com . Minimum order there though! To check the petcock, with the engine off, pull off the fuel lines to the carbs and turn the petcock to ON. There should not be any fuel coming out of the fuel lines and no fuel in the vacuum lines either. If there is either, you will need to do two things; check your crankcase for a gasoline smell; if you smell gasoline, change the oil after you rebuild the petcock. What can happen is when the petcock fails, it can fill the crankcase full of gasoline and that can cause you to blow the engine due to a lack of lubrication. Never leave the petcock on prime when the bike is setting as these carbs can have a float stick or not close all the way and again you will find your crankcase full of gasoline.

[bstig60]

You need to make sure the petcock isn't leaking. It sounds like it is. If so, it will need a new kit put in it. They are available at www.partsnmore.com . Minimum order there though! To check the petcock, with the engine off, pull off the fuel lines to the carbs and turn the petcock to ON. There should not be any fuel coming out of the fuel lines and no fuel in the vacuum lines either. If there is either, you will need to do two things; check your crankcase for a gasoline smell; if you smell gasoline, change the oil after you rebuild the petcock. What can happen is when the petcock fails, it can fill the crankcase full of gasoline and that can cause you to blow the engine due to a lack of lubrication. Never leave the petcock on prime when the bike is setting as these carbs can have a float stick or not close all the way and again you will find your crankcase full of gasoline.

[El Cheapo]

My bike had two major problems when i originally posted this, then an extra major problem after i fixed the other two problems. All were of the carburater.
-Problem #1 was that the bike was only idling with the choke on atleast halfway. I fixed this by thoroughly cleaning the carbs. The cause of this problem was that one of the rubber o-rings, located on one of the fuel/air mixture screws, was completely chewed up and disintegrating and blocking up one of the carbs' pilot circuits. This is the circuit that is in charge of idleing. The other two ciruits are the starting circuit or choke circuit, which is for cold starting, and the main circuit, which kicks in when you have the throttle open. My idling problem was a blocked pilot passageway.

-Problem #2 was that one of the floats was fuel logged. This was causing only one cylinder to fire because the failing cylinder was getting flooded out because of the float that wasnt floating. I originally identified this problem by switching the floats, and observing that after that, the problem switched cylinders.
After i suspected the float failing, i weighed both floats on a sensitive scale and noted how grand the weight difference was. The failing float was 2 grams heavier than the functioning one. After that, i bought a new float.  This brings us to the final problem.

-Problem #3 was that the new float was not bent to the right specs when i got it, and so, it was sticking inside of the float bowl, failing to stop the fuel flow, and still flooding the cylinder.. it was a similar problem as the fuel logged float, but different too. Although the "float tang," was set correctly, and the fuel level was set about midway up the bowl, the float would still need other bending.
The new float was behaving differently than the fuel logged float because it was functioning correctly at first, and both cylinders were firing, but eventually, it would stop working, flood the cylinder, and then only one cylinder was firing.
It was extremely annoying for me to figure this one out, but i did eventually.
The new stock float originally came bent to certain specs that were close enough to work inside the float bowl while it was cold, but as soon as they started getting hot from riding it for awhile, the float would expand length-wise, and the outer tip of the float would get hung up on the inside of the float bowl. This caused a flood of fuel to the cylinder, making it fail. I bent the float inward a bit, and now its fixed. Both cylinders firing all the time now! I'm riding it everywhere! Cheers! If this helps, let me know. Goodluck!

[bstig60]

Thanks for the info. It's always a good idea to bench set the floats before putting the carbs together, then check for clearances.

[stingypaperwaffles]

ANOTHER UPDATE: Well, the leaking petcock diaphram wasn't all of the problem. It still misses out until warmed up, then cuts out sporatically when it is cold out. I checked my plug caps again, found the front one way out this time, took them apart, and the resistor ohmed at around 20k, then when I'd heat it with a lighter, the ohms would drop, all the way down to 3k. I thought for sure that was it, it made sense, high resistance when cold = misfire, low resistance when warm = runs great. I found perfect NGK replacements through O'Reilly's, p/n NGK 8020. (BTW, the 8020's are for use with the nut on the threads on the top of the plug, not like the OEM's. The one's like the OEM's are p/n NGK 8030, but the 8020's were all that were available from their distribution center, and the new plugs came with the nuts anyway, so no big deal, plus now I can use the generic inline spark tester on it, which is handy) Well, it certainly ran better, but the problem was not solved. So, I swapped the coils again, this time the problem stayed on the front. Now I took out the TCI (I figured out a trick to get that out, surely someone else has figured this out, but here it is: I had read somewhere, maybe in Clymer's, to drop the fender to get to the TCI, well that is a pain in the butt. So, take out the battery and the box, and it comes right out. But, before you put the box back in, drill about a 3/4" hole in the battery box, right in front of the lower screw, factoring in the screw's angle. Now you can get it with a stubby screwdriver just by taking out the battery) Anyway, I took out the TCI and had it hanging on the side and started the bike. BTW, it runs perfect now at idle, but cuts out at 2k-3k RPM's until warmed. Then I blew a hair dryer on the TCI, and the problem was gone within seconds (I had the inline spark tester on it, it went from barley on to bright), it used to take around 5 minutes to go away on it's own. So, I started by replacing the transistors (found what seem to be good replacements at Radio Shack, they are 75w, good up to 300 degrees, p/n 276-2020, less than $4 for the pair and tax), made no difference. Then I touched one of the capacitors just barely, and it smoothed out. I figured out that I could just barely move the board back and forth ever so slightly by that capacitor, and make it cut in and out. So I am now in the process of resoldering the joints and we will see where that goes. I am finally very confident that I am just about finished with this stupid, extremely annoying problem, just in time for winter

[stingypaperwaffles]

Well, I guess my Radio Shack transistors may not be such a good replacement in the TCI after all. I finished resoldering everything, and it ran strong when cold, but it would miss out bad at take off. I put the old transistors back in, and now everything is perfect so far. I will keep my fingers crossed and consider it fixed if it doesn't act up any over the next few weeks. Also, forgot to mention on the TCI removal shortcut, you also have to remove the seat, the left side cover and compartment in addition to the battery, but still much simpler than removing fender in my opinion...

[bstig60]

Hope it works for you. The enemy's of the TCI's are time, heat and vibration. Those that rebuild the older ones put in components that have higher heat tolerances and then add solder to all the connections, then refill with Gel to help control the vibration. Heat was the main reason the design was changed and the TCI relocated from under the fuel tank to the position in front of the rear fender. I have an older bike, so I had my TCI rebuilt and I keep a spare TCI in addition to my spare set of carbs.

Bill

[stingypaperwaffles]

Well, I am happy to report that after several cool morning (and dense fog) trips, I have not experienced a single hiccup that a choke adjustment did not solve. I could not be happier, unless I had a 6th gear and a bigger tank. But at least I can jump on and go whenever without having to warm it up and worry about it cutting out while I'm trying to pass someone. Now I can focus on cosmetics, and getting the rebuild for the petcock. Yeah, I know vibration is probably enemy #1 of the TCI. I figure being mounted on the plastic fender has to help. When I put mine back in, I used rubber washers underneath the TCI and under the screw heads. I figured it couldn't hurt anything. Anyway, thanks to all for the advice. Later...