Gimpy left cylinder

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May 11, 2007
Now my newest problem to pop up is that my left cylinder only occasionally fires. It'll still start with two or three kicks with the choke on and stay running, but the left side will only fire here and there. When revved up it'll fire more but still not consistently. It fires pretty consistently under acceleration though. Left plug is soaked with gas if I pull it after just idling, and I can definitely hear/smell/feel the difference coming out of the pipes - right side everything's normal but I only get this "chuff chuff chuff" out of the left and it stinks like gas, basically just acting like a big air/gas pump.
I switched plugs, leads, coils, problem doesn't switch sides. Just put in new AP64s to replace the NGKs, thinking it was just weak spark. I get a better spark now but it didn't change the firing problem. Just timed it a couple weeks ago, and haven't put 50 miles on since then, mainly because I can't get it running well enough to leave the neighborhood.
Retorqued head and reset valve clearances. All the valves seemed to move ok, and no broken springs or anything. Compression was about 150 on each cylinder.
I have a single MkII carb so that rules out one of two carbs just flooding a cylinder. Dismantled that in the process as well and didn't notice anything abnormal - jets looked fine and no air leaks around the manifold that I could tell. Needle's moving fine too, with no binding or hanging on the edge of the jet.
I'm at a loss. My gut feeling is an electrical problem but aside from timing and checking grounds to the ignition, I'm not sure what else would cause this on just one side. I'm praying it's not something with the head since it hasn't even been 75 miles since I had it rebuilt, but if it's not electrical what else would it be?
If you are running two six volt coils with a boyer wiring them in series as the directions require has one coil firing normal and the other firing backwards. Sometimes the difference is readable on the plugs. You might try switching the coils keeping the wiring the same or changing the wiring around so that the power flows the opposite way around through the coils as they sit. Watching to see if the problem moves. At one end of this circuit you will find that the ground has to be very good it's how the power finds it way back to the battery. I think I recall you running a Boyer.
I have a Pazon, but the coils are also wired in series, I'm guessing just like the Boyer from the sound of it. I'll give it a shot if it decides to stop raining anytime soon...
So even if your running a single coil with duel output it works the same way. Switched power goes in on negative of the first coil comes out on the positive of that first coil and jumpers out to the negative of the second coil. Now the important part the positive of the second coil must go to the common ground on the frame and a single wire from the positive of the battery must also go to that common ground. A dedicated ground wire from the head to the common ground is also a requirement. The ground wire for the Pazon needs to be on the common ground as well as the ground for any rectifier system you are using. There should be a ground in the harness that needs to tie in to common as well and of course one from the brake light.
I use a braided ground strap from the head to the upper head steady bolt and run a doubled wire ground back from that bolt to the common ground.
Ah, and the light bulb pops on in my head.... Must be a Lucas bulb since it takes a while sometimes. :roll:
That's probably my problem then, thanks norbsa. At the moment the only grounding for my coils is a wire running into the harness, which then gets routed god knows where until it finally reaches an actual grounding point on the frame. I'll try running a dedicated grounding wire from the 2nd coil directly to the headsteady. I think I have some heavy-duty wire around here to run one directly from the battery + terminal to that point as well.
Best spot for the common ground is the old rectifier mounting tab. So that the battery heavy cable is short.
I had a not-dissimilar problem lately. Ran another lead from coil positive connection to ground (cylinder head) and the baby runs like an angel now. FWIW. - BrianK
I just ran three 12 gauge cables - one replacing thing smaller one going directly from the coil to the head, another one from that point on the head to the frame under the headsteady, and I also put one going directly from the + battery terminal to the back of one of the bolts mounting the left Z plate for good measure. I also tried swapping only the connections instead of the coils and it still barely fires on just the left side. Once moving, when I'd accelerate with a moderately open throttle it didn't miss a beat. But if I'd try to run it at slightly open to cruise it would start missing again.
For some reason I got the urge to disconnect the blue capacitor. It was harder to start and after it did the left cylinder almost never fired even when revved up. Now I'm completely lost...
Brand new batteries can be "bad" have it load tested by someone who sells motorcycle batteries. A crude test can be done leave the head light on for three minutes than leaving it on check across the batteries poles with a meter it should still read about 12.5 volts. Your condenser having a positive effect on the running is a good sign for it's condition old ones are not worth buying, when in doubt disconnect it, protect the hot wire with some tape.
Your new ground wires are doing no harm but you need to get the concept of the common ground system down pat. All the major consumers of juice in the system need a copper contact back to the positive of the battery post. You are trying to keep the system from using the frame to conduct electricity.But you don't want seven red wires running to the battery terminal that would cause corrosion. So you need to run these return pathways back to a point on the frame near the battery. Then one thick wire from the battery to this point. The way you have done it the ground could still be using the frame on it's pathway to the battery. Your symptoms sound like a bad kill switch,or a key switch, or a bad set of Boyer wires.
I'm with Pops on this one; it sure sounds like a bad ground. And as he suggested, check the Pazon lead to the left cylinder to make sure it's not just making partial contact. Don't get too frustrated, you'll find the problem.
I apologize in advance for this novel of a post, but... I finally had enough small windows of time during the past few weeks to work on this problem and now I’m even more confused than before. Last night I did some temporary rewiring to completely eliminate anything that wasn’t the ignition. I sent a wire directly from battery negative to the white wire in the Pazon. The coils (6V) are in series as specified, and I have three ground wires tied into the + post on coil #2: the red one coming from the Pazon, one to the left side headsteady plate, and one going directly to the + battery post. I also have a braided grounding strap going from the headsteady plate to battery + as well. Basically grounded the hell out of it, at least I thought. I know everything should technically be going to a common ground and not directly to the battery but I’m trying to get as direct a route to/from the battery for the moment. All other wires coming from the Pazon are connected as specified.
Even with all this the left side still won’t fire. To make matters worse, after a few seconds of running on the other cylinder the left pipe was leaking gas. It was filling up the header enough that it started running out of where the muffler clamps on. It had started doing this before but it was usually just a couple drops. This time it was bad enough that it actually made a big puddle on the garage floor.
Checked compression again and it’s dead even between the two cylinders, about 150-160 depending on how hard I want to kick. Checked the connection between the trigger plate and trigger wires and it’s good. Even checked the strength of the magnets on the rotor for the trigger and they feel the same. Did a spark test by touching them together and both plugs fire as long as they’re dry, i.e., not just out after trying to run. In that case of course the left one’s soaked and won’t fire. Valves are adjusted and look to be moving properly. Did countless other checks that I don’t feel like listing since this post is long enough already.
So… is it time to take the head off, or does it still sound electrical? If compression’s good I don’t know what in the head would cause this. Symptoms point (in my mind anyway) to an exhaust valve sticking open – is it possible that it only sticks when the valve starts moving at typical engine speeds? But even then, wouldn’t that still show up doing a compression test? Electrically, if the thing’s hooked directly to the battery with no accessories running what else could it be? I haven’t gotten the battery formally load tested yet, but every test I’ve done with a multimeter came out ok. I checked and electrically there’s virtually no resistance between the headsteady plate and the head, but does there still need to be a line connecting them? I would think the bolts and headsteady plate would be good enough conductors.
One thing I did notice was that, with the plugs out, they seemed to fire weaker when kicking the engine over as opposed to when I touch the trigger wires together, and sometimes didn’t fire at all. At first I thought this was because of the slower engine speed when kicking over (Pazon states a minimum cranking speed of 100 rpm) but now, who knows.
I have the Pazon unit itself mounted right between the coils – could electrical interference be an issue? I think the consensus before was that it shouldn’t be, but my mind’s going through every remote possibility at this point…
Keep chasing the electrical aspect... The simple load test is head light on three minutes leave it on, check battery volts. If it passes that test your good, it needs to read 12.5 or better for this test your just removing the surface charge. Just for kicks try new plugs. Even if the ones your using are new.
Is it possible that the cam lobe has went away? It would still have good compression but no power. Just thinking out loud.
Good grief, there Scheffy; I am beginning to feel your pain!

Now it sounds as if the left carburetor float is stuck wide open, especially with gas dribbling from the exhaust pipe.

I'll keep thinking, but don't take your head off yet.
If the cam lobe is worn down the valve would stay closed longer and have less lift, so wouldn't that actually result in less gas coming out? I could probably check valve lift when i get home anyway. That's one thing i haven't checked yet.
I'm running a single Mk2 which makes it both simpler and more confusing at the same time. Simpler since it (probably?) rules out a carb problem since one cylinder's working, and more confusing since... well, really for the same reason.
There's not really any real smoke coming out the left side, mostly just white-ish/grayish puffs of gas. On occasion when it does fire, usually at a higher rpm, it's a black puff which i'm guessing is a big wad of built up gas finally being burned. When it was running both used to smoke a little only when the choke was on, and needless to say it didn't like running on choke for very long (standard Mk2 behavior, so i've heard). I haven't been able to keep it running without the choke on since this started though, probably because i won't run it long enough to warm up too much.
I'll run out and get some more AP64s. Wonder if they give bulk discounts...?
If the right-hand cylinder appears to be firing as it should, then with the Pazon system (or any wasted spark system like Boyer or Lucas Rita) the problem can ONLY be due to one (or more) of four things, IF it is an ignition related problem. Those things are plug, plug cap, spark lead or coil on the L/H side.

If you have replaced/swapped all those things over, then it is unlikely to be an ignition fault.

The possible carb flooding symptoms does sound as though it needs investigating further.
It just occurred to me when i was at the store to check whether AP64s are resistor/non-resistor plugs. I assumed they were non-suppressed, but lo and behold they're resistor, which between that and my resistor plug wires probably didn't help matters at all. By the time i put those in the NGKs i had in before were probably already fouled beyond repair from sorting out my carb problems so they ran even worse than the APs despite being non-suppressed. Long story short, i picked up some more BP7ES's to try with my current wiring setup.

My mistake about the carb. I forgot you had a single carburetor, which makes my stuck float comment sound really stupid. By all means try a fresh set of plugs.
Could you swap plug wires right to left and left to right cylinder? If the right cylinder is missing, you could eliminate internal engine problems and know for sure it is an electrical problem. I'm new to Nortons but I think this would work. Good luck
Finally got it firing yesterday! I ended up completely removing the coils and associated wiring to once again check things and reassembled with some slightly different grounding. Three from the coil +: one to Pazon ground wire, one directly to battery (will eventually go to common ground somewhere), and one to headsteady side plate. Also ran a short one from one of the headsteady-to-head bolts to one of the side plate bolts for good measure. Left the ignition directly connected to the battery to test. Also put new plugs in. After a couple kicks it started up and was firing both sides. Plugs show the left still leaving a little more soot than the right but at least it's dry now. Moral of the story is when in doubt, it's probably electrical. Grounding grounding grounding...
Now the issue is it wants to idle at 3K rpm but when I checked again just before bed the throttle cable was binding a bit and the plastic mixing chamber top wasn't completely screwed on, probably letting a good bit of air past, so after righting those the problem may already be fixed. I'll start it tonight quick to see. If not, prepare for the next barrage of questions...
Anyway, thanks everybody for your help. You very well may have saved a Norton from a frustrated push down to a watery grave... :lol:
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