Forum

[John R]

Good compression, fat spark, carburettor clean and as well as adjusted as I can manage. Not firing apart from the very occasional little sneeze or kickback. Having racked my brain for all other theories, I'm wondering if it's possible for one of the coils on the Boyer ignition sensor to have failed independently of the other. (you may be aware that boy ignitions use a wasted spark system. Therefore, is it possible for the spark to be occurring only on the wrong stroke)?
I'll try Boyer in the morning, but just wondered if anybody had any bright ideas today?

[simon]

Sounds like a timing issue to me. You can dip the spark plug in petrol and see if it fires properly to exclude carburetion but if the plug is already wet when you pull it out it probably won't change anything. My guess would be that you've got the static timing wrong.

[Gwilly]

Need more info really John. What boyer is it? Was the bike running ok last week but now won't start? Or rebuilt and won't fire..

If the former, then check the fuel for water in tank or float bowl.. If you have a GM or Gel battery they are prone to sudden failure and depending on boyer type can play havoc with the timing being way too advanced usually.. Maybe you are batteryless and running a capacitor or power box, lack of output here could have a similar effect on timing..

I like the pick up coil theory, would be a very rare occurrence but not impossible. Perhaps check ohms resistance on each coil, doesn't matter what the value is as long as they are both similar.
Maybe you can check your theory by simply turning the back plate through 180 degrees, timed to opposite coil.. Wish you luck anyway. gwilly.

[Norm]

You should be able to tell by the number of times it sparks, it will fire the plug twice as fast as normal points ignition

[John R]

Giving it some thought, the wasted spark theory doesn't really work; there are two magnets, so even if one coil was duff,the other would still be triggered every stroke. I have redone the static timing from scratch and it makes no difference.
It's a MK4 Boyer, I have a battery and a power box, bike is an '89 350 breathing through a 26mm Amal Mk 1 Concentric. I have a Goldie style exhaust. All this worked very nicely indeed until recently, slowly becoming more temperamental and difficult to start.
I have tried different plugs, I will try a Mikcarb. I believe the battery is good, but will try another.
If that doesn't work, I have to assume that Laws of physics and chemistry are temporarily suspended in my bike's combustion chamber.Can anyone recommend any deities, possibly in the Hindu religion, who might have dominion over this sort of thing, and what sort of supplication or sacrifice might appease them?

[Bullet Whisperer]

Hi John, a long shot here, but it happened to me on a 350 Bullet once - has the needle dropped out of the clip that holds it in place on the slide? Easy to check for and fix. Regards, Paul.

[John R]

No, BW, I had that happen once and I have checked it.

[Bullet Whisperer]

O.K., long shot No 2 - are the pushrods both engaged properly at both ends, with both valves opening and closing as they should? As you mentioned the trouble gradually developed, I am wondering if a pushrod adjuster has come loose, or another one I have seen recently was the top of a rocker block's four nuts undoing and the inlet valve barely opening as a result, the engine would spit and fire, but not pick up and run, as you describe. If anything else comes to mind I will add it later. Regards, Paul.

[John R]

As checked via the tappet inspection cover, the valves seem to be operating correctly and to be correctly adjusted.It might be worth looking at the rocker blocks, but I think you could tell if that was it

[Thack]

That little sneeze/kickback suggests it's too weak. I bet it'll be something to do with the fuelling side of things.