Starting Woes

I just finished rewiring my '73 after a roadside breakdown. The whole headlight wiring harness fried. While I was at it, I rewired the rest of the bike, too. Lights all work. I have spark when I kick it over. I have spark when I hit the kill switch. I'm running a Boyer black box, which is practically new. Battery completely charged up. Gas in the carb (Mikuni). Compression good. Tried changing plugs. Checked if timing looked right. It looks OK to me, and I haven't touched it. Last night I kicked it over after finishing my wiring and evntually I got it to come to life for a second. I knocked off because it was 2:00 in the morning and didn't want to wake the neighborhood. Now when I kick it over, nothing.

The only other thing I've changed was to put in an angled tube in the top of the carb to give more clearance from the tank. Could it have altered the cable in any way to cause the slide to lift slightly in the carb body, or does that not make any sense? I hate to ever use it, but, I tried a shot of ether and all it did was pop. I can see if I wired anything wrong that the bike wouldn't run, but with a spark you'd think there would be at least some signs of life.

Any help is greatly appreciated. I'd like to get this beast back on the road!!

Bad luck. I'm sure you'll find it if you check methodically.

Is it sparking if you rest the plugs on the head and kick it over ?

Could the leads from the Boyer pickup have become reversed ?

Real common to foul plugs testing.

I did lay the plugs on the head and kicked over. I get spark. I'll have to look into what you say about the Boyer leads. I will say I haven't touched a thing on it, however. Maybe I wired the harness leads incorrectly to the Boyer system itself? Cookie, as far as the plugs are concerned, I did put brand-spanking new ones on thinking that fouling might have contibuted.

How long has the gas sat in there since your breakdown? You might want to try a fresh tank; make sure to drain the float bowls to empty them of old stale gas before you try to start er up again.

You'd be amazed how much difference this may make....

And if it DOES work (and maybe even if not...), you should probably run a can of Sea Foam (or equivalent fuel system cleaner - Techron, Redline, B-12, etc.) through your next coupla tanks of gas.

Good luck.

I put the gas in there probably 3-4 weeks ago, but you could be right. I'll try that. I did have the carb apart today and made sure everything was tip-top. I never have tried the seafoam but heard good things about it. Of course, seafoam won't matter if it isn't running! Also I checked the wiring on the Boyer as suggested, all looks OK to me. White wire to kill switch. black to coil, red to ground, and leads to pickup in timing case. I'm about ready to put candles around it and pray to the demon gods if that'll help.

It's possible to pick the wrong timing mark on the rotor in the primary. You have to pick the one that comes in the window when the pistons are coming up. DAMHIK. A pencil or a flashlight is all it takes.

bpatton said:

It's possible to pick the wrong timing mark on the rotor in the primary. You have to pick the one that comes in the window when the pistons are coming up. DAMHIK. A pencil or a flashlight is all it takes.

Click to expand...

Thing is, I haven't touched anything on the primary. The timing is intact. I checked the piston vs. the rotor to make sure nothing slipped just to be sure, but I've not done anything at all to the timing, wiring, both to and from.

spark, compression, gas
gas> even living here in hot new mexico, still have to depress the mikuni choke and kick hard when motor cold, choke?
petcock on, remove mikuni lower chamber, gas in it :? no insults, just my check list when will not fire

No insult. Have gone throught the drill numerous times. Choke, Compression, gas. Even took the opportunity to take off the petcocks and clean them thoroughly while I had the tank off. I emptied the tank and let it dry. I drained the float bowl, too. Put in new gas and then....left it there 3 to 4 weeks while rewiring the bike and attending to life's other duties. So far, that's the only thing makes sense to me, but I guess I put old gas at the back of my mind since I've made such major changes in the whole electrical system. Kind of getting tunnel vision maybe. If there were no spark, that would be one thing, but I'm getting fire, so.......guess replace fuel next. Everything else on the bastage works, so I have to be thinking fuel, carb, air.

I know it sounds silly SlupDawg, but have you checked you've got the right spark on the right cylinder?

davamb said:

I know it sounds silly SlupDawg, but have you checked you've got the right spark on the right cylinder?

Click to expand...

OK, can you please explain? My thinking is that nothing at all was altered in regard to the wiring sequence of the coils or the pickup. I left the entire Boyer system intact. In fact, the only way I involved it when I rewired was to wire the ground wire to the new harness. The other wires connect to the kill switch on the handlebar and from the boyer box directly to the coil, none of which which I touched, nor did I involve the leads to the timing pickup. The spark to each cylinder worked fine in the past, so I'm thinking nothing has changed since?

Oh ok SlupDawg, I thought as you'd rewired the bike there was a chance you had the points (or Boyer in this case) and ignition coils transposed, i.e. left points connected to right cylinder coil and vice-versa on the other pot. I know someone who made such a mistake in the early days of trying to get his Norton running . But if you've never changed any of that part of the loom, there's no way it could be incorrect.

Boyer unlike points is a wasted spark, both cylinders get a spark every 360 crank degrees so you cannot mistime the wrong cylinder. Points do not have a wasted spark so with points you can get the sparks coming at the wrong TDC.

You've obviously had a colossal short circuit and anything could be damaged so nothing can be taken for granted. If there is a bad contact, the Boyer will be advanced. This will often give pops and bangs but sometimes nothing. Try running a live from the battery to the Boyer live (white).

It can also do no harm to try reversing the leads from the pickup (black / yellow and black / white) This can cause odd malfunctions.

Have you got 12.5v at the battery ? It may not have taken kindly to a dead short.

Multimeters are very cheap, less that $25. Check the voltage to the Boyer. What caused the original meltdown? Are you using an ammeter?

ah, the infamous intermittent boyer GROUND wire?
I remember having this starting problem.............

bpatton said:

Multimeters are very cheap, less that $25. Check the voltage to the Boyer. What caused the original meltdown? Are you using an ammeter?

Click to expand...

Just what I did. Firstly, I've changed out for fresh gas. No love there. Then I've checked the voltage at the battery, which seems a little low, but I haven't trickle charged it for the last 2 days. 12.55V at the source. I checked the power into the box. It's 12.28V, almost .3V dropped, which doesn't sound good to me. The other day the battery voltage was right at 12.8, with the same results. What's the max voltage drop allowed to the box? I'm assuming old wiring in the headlight shell finally gave in and wore down the insulation on a couple of wires and it melted the wires leading to the bulb adapter together, shorting the bike out.

highdesert said:

ah, the infamous intermittent boyer GROUND wire?
I remember having this starting problem.............

Click to expand...

I had that happen before too. That's why I got a new box. The old one had intermittent trouble that I could never find, so got a new one. This isn't the same, though. It sparks every time. The other box would only occasionally.

When I had an electrics meltdown and rewired my bike, I only had the wiring diagram from the manual, and so accidently linked the coils they way they would be for points and not for the boyer ign. The symptoms were the same as described here.

I have a couple of other silly things to mention. A friend had no spark and it turned out his Boyer had to turn over fast enough on the kick to spark. Draining ht oil in the sump fixed that one. Another time we had a no spark which turned out to be due to a painted head my friend thought was bare. His plug got no ground for testing. That one was a fuel problem.
I think my Boyer was starting to get crazy at about 9 volts to it. I've heard it needs more than seven but other here know better than I do. I pulled it after it bit me once.