Right Cylinder Not Firing

[Snirp]

I can't find any previous discussions that describe this as my bike is experiencing, so here's a new post.

1980 Yamaha XS650. Ran a few years ago, parked and now getting it going again. Combustion in the right cylinder is only occurring like 10% of the time if that, but it does happen here and there. Left cylinder is great, running strong

• Engine rebuilt with a 750 BB kit
• Not rephased
• All new internals
• Dellorto PHF 36 carbs
• Boyer Brandsen Micro Digital ignition, Red box
• Hughs Hand Built PMA Charging System
• Anti gravity Lithium battery always on a tender, reading 14 volts
• Disconnected battery anyway and hooked up regular battery from my Harley, no change in condition. Harley had 12.5 Volts
• Switched carbs from side to side to see if condition moved, but condition did not change, still no combustion on right side.
• Floats are good.
• Spraying fuel in the right side open carb doesn't seem to do anything, still no combustion in right side.
• Spark at both, visually checked by grounding plug to engine and also had timing light hooked up in line with plugs. There is spark at each.
• Timing checked, spot on firing at advance mark.
• Coil was new, but replaced it anyway as I'm at a loss here. New 4.5 OHM coil does nothing really, but right cylinder did run a few more times here and there.
• NGK plugs switched side to side, plug wires switched, no change in condition.
• Compression is at about 145 each side
• Valves have been checked when cold, no adjustment was needed. spot on.
• Head was rebuilt at an engine shop

Engine ran well after the rebuild, then I let it sit as I had kids, no time for anything. Getting it going again. Very frustrated and I'm loosing my mind. I have no clue what to do next, where to go with this thing.

Advice?

 

[Jan_P]

I would flip the Boyer wires
Right to left and Left to right
Please do the read up but Boyer is Usually waste spark

And recheck ignition wiring

Just to be sure --but the spark is weak as first assumption

 

[Its been a long time]

I would flip the Boyer wires
Right to left and Left to right
Please do the read up but Boyer is Usually waste spark

And recheck ignition wiring

Just to be sure --but the spark is weak as first assumption

Yes, we need to know the voltage at the coil +ve terminal. But both plugs fire together and one of the cylinders runs OK.

I would look for an air leak on the inlet manifold of the poor running cylinder.

 

[Snirp]

Excellent thanks, I have not seen that advice before. I'll do that tonight and get back to the thread. I agree, weak spark I think is the buried issue here, and I'll ensure no air leaks.

Thanks guys

 

[Snirp]

I finally got around to checking:

• Flipped the wires leading to the Boyer timing at the cam, the bike wouldn't start.
• I flipped the 2 wires leading to the coil. The bike ran, but backfired a few times on the right side (cylinder giving me trouble).
• Checked all wiring. Connections are fine.
• No air leaks, everything is tight.
• I pulled out each plug and grounded to the engine, no quick spark when ignition turned on or off. I read online typically there is a quick snap/spark when the ignition is turned on or off with Boyer's. Not sure if this is true...but regardless, mine did nothing.

I think the issue is the red Boyer ignition box. I tried to upload a video I took of the timing light on the timing marks, but it wouldn't upload. The timing light is almost constantly on for the right side, left side is better.

I hear the boxes aren't interchangeable from a distributor on eBay, meaning I can't just get a new Blue box and install to my existing wiring/parts. Not sure if that's true. The Blue box is the most current model. I was hoping to do that to save money. I don't have the original points ignition either to install/check against.

So, I think I'll be looking for a red micro digital box to replace this one.

Let me know what you fellas think.

Chris

 

[GLJ]

Boyer red and blue boxes do not interchange. Each uses a coil specific for the box.
I think and this is only a guess is you could use a blue box if you also get the coil that goes with the blue boxes.

 

[Jan_P]

Not sure if I got trough #2
If one side is running on the Boyer .switch the Spark plug wires
Keep other as is
By switching ---pull them off the spark plug top and reroute to other side
Hope wires are long enough

You can also take both plugs out and ground them against the cylinder head
With kick you shall be able to see sparks on both plugs --Not heavy to kick with plugs out

 

[Snirp]

I have swapped plug wires, bike won't start. Backfires from right/dead cylinder.

I have switched the ignition wires running to the stator, same condition as above, won't start, backfires.



Good idea to kick with plugs out, I did that and saw spark at both plugs as I kicked it.



The boat anchor lives in as a boat anchor.... I'm at such a loss here!!!



I wonder if the ignition is "working" but producing a weak spark somehow. Coil is new. I'm considering just ordering a new red box from Boyer to see. I hate throwing money at issues hoping to fix it, but I have no idea what to do.

 

[Its been a long time]

Personally, I would expect the Boyer Bransden box to either spark or no spark.

As it's a non standard charging system I'd be double checking my timing marks with a degree disc before doing anything else. Then I'd make sure I had a solid 12v at the coil and the ignition box. Anecdotally, it seems the BB system needs a good solid 12 to work at their best.

 

[Jan_P]

I was to slow Mr Ibalt was quicker

If there is spark with plugs out grounded to head --- looking even the first assumption is the Boyer is OK I am Busy right now
So have not read through .Can save some money if waiting for others to chime In

Next would be to measure what Voltage is at the Coils and Boyer box Apologize if already mentioned

 

[arcticXS]

Visible sparks with the plugs out and grounded does not necessarily mean good sparks when inside the combustion chambers at 150 psi or more. I would definitely check voltage at coil + terminal at whatever position there is a current flowing through the coils. Or is there a set "dwell time" in the Boyer, making this check difficult or impossible? If that is the case, supplying the coils directly from the battery with a temporary wire with an inline fuse will tell if you have too much resistance/ voltage drop between battery and coil +

 

[Snirp]

So, I checked again for a few things:

Battery is sitting at 13.2 V, charges at maximum 13.25V.

Coil Ohm is at 4.5, but I get no reading going from one of those lead wires and connecting to either plug wire. Switched all through each thousands settings, no reading. On the new coil currently installed, or the old coil. Both read 4.5 ohm, with nothing connected to a plug wire. Shouldn't I see a reading around 10K??

Coil is supplied directly to the battery inline, no fuse.

How do you check voltage at the coil, and the Boyer?

 

[Jan_P]

Dont have power on the coil all the time it can fry