Misfire LH cylinder

This has been a consistent gremlin, and I've gone through most of the usual suspects but I'm hoping that listing these items out will help solicit something I hadn't thought of yet, regardless of what I've tried, the problem remains only with the left hand cylinder:

Carbs - new twin 30mm JRC's. I've nearly got the jetting dialed in, just waiting on Commando needles and #30 pilots from JRC (Awesome service, really great folks IMO). Float levels dialed in, she runs beautifully at anything above idle, only thing left to change are the pilots and I think she'll be set in this regard. The problem also existed with the old amal's as well so I'm not suspecting the carbs any longer.

Valves - Lash is correct, tried moving up to 10K/10K, 10K/12K, 12K/13K with the thought that maybe, just maybe the PO may have installed an aftermarket cam. No change.

Wiring - Good solid, copper battery strap from head to head steady mount. New ignition switch. All connections tested and solid, good ground throughout.

Coil - running a dual output Dyna. Both plugs/wire have been swapped. Now my thought is if it's a coil fault both cylinders should be acting up with a single coil... correct? Am I missing something here? Should I try switching the positive/negative wires? Would it even make a difference?

Boyer Plate - Now this is where more confusion lies on my part. Checked the pick up plate, no busted solder, no cracked wire. I have the wires insulated from vibration both through the case channel as well as under the rotor cap. Although I couldn't get a resistance reading between the pick up coils, but I'm probably doing something wrong.

Boyer Box - Straightforward wiring. Wired directly to ignition switch, leads from pick up plate are solid and properly insulated from vibration, black/red to coil... nuff said.


Now my question for all you norton doc's out there is this; Is it even possible for a Boyer, wired in this fashion with a single coil, to cause a single cylinder misfire? Thanks everyone.

Sounds like you have been pretty thorough. It would be nice if you could borrow another "black box" and a plate, but baring that it sounds like you may have some stray capacitance lurking in the box or on the plate that randomly discharges causing your misfire. Do be sure that all your connections are made well and that each part of the ignition system is tied to the ssame ground, even if you have to add another circuit. Do check the solder joints under the plate, maybe even re-heat/melt the solder, using a low wattage pen or gun. Given the nature of the electronic ignition I'd throw my betting money on a bad plate.

RS

Boyer Plate - Now this is where more confusion lies on my part. Checked the pick up plate, no busted solder, no cracked wire.

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You won't see anything visually. The wires will crack inside the insulation. Check out the wires with an ohm meter. You said you could not get a resistance reading between the coils. Open or short? If it's an open, that indicates a problem. The resistance should be very small. The following is from Boyer's website:

HOW DO I CHECK THE STATOR PLATE?
A full visual check of the condition of the circuit board and coils looking for loose or broken parts. Check for signs of the rotor touching the solder connections. Using a multi-meter check the resistance of each pickup coil and then the total resistance across the wires or terminals. With the meter still connected, run your fingers round the coils, if the resistance changes there could be a broken winding inside.

I believe the resistance should be 135 ohms or so, placing the leads on the black/white and black/yellow wires to the plate.

I did find a dead magnet and a very weak one on the rotor the other day--the magnets should support the rotor's weight when suspended from a flat ferrous surface.

With a voltmeter on the black Boyer wire feed to the coil you should see varying voltages as you kick through with the ignition on--anywhere from 1.5V to 10.75V. If the black box isn't switching off the coil in this way the bike will never run satisfactorily. It's counterintuitive the way the black boxes sometimes fade out without going completely dead sometimes.

Good luck, and let us know how you fare, if you would


Tim Kraakevik
kraakevik@voyager.net
Three Commandos

JimC said:

Boyer Plate - Now this is where more confusion lies on my part. Checked the pick up plate, no busted solder, no cracked wire.

Click to expand...

You won't see anything visually. The wires will crack inside the insulation. Check out the wires with an ohm meter. You said you could not get a resistance reading between the coils. Open or short? If it's an open, that indicates a problem. The resistance should be very small. The following is from Boyer's website:

HOW DO I CHECK THE STATOR PLATE?
A full visual check of the condition of the circuit board and coils looking for loose or broken parts. Check for signs of the rotor touching the solder connections. Using a multi-meter check the resistance of each pickup coil and then the total resistance across the wires or terminals. With the meter still connected, run your fingers round the coils, if the resistance changes there could be a broken winding inside.

Click to expand...

Thanks, when touching the leads to the two pick up coils I get no resistance... am I testing this correctly?

http://www.tioc.org/boyertest.htm

Follow the diagnostics carefully as shown on this website--good luck



Tim Kraakevik
kraakevik@voyager.net
Three Commandos

I don't see how, if the bike runs correctly at higher RPM, that the ignition system per se could be the issue. Normally a faulty ignition system is a problem under power before it becomes a problem at idle. There is no real load on an ignition at idle. OTOH, since the boyer is well known for problems with low batt voltage and there is no charging at idle, it is possible that it's simply a low voltage issue.

Did you do any voltage readings at idle - According to all the data I have seen, analog Boyer's don't like anything below 12.5v. I'm not sure how that would actually end up being a bad spark on one side with a wasted spark system but it's worth checking.

Thanks, when touching the leads to the two pick up coils I get no resistance... am I testing this correctly?

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By no resistance do you mean zero ohms or infinity? Your multimeter should be on it's lowest scale and read some small resistance. Wiggle those wires when you do the testing. The Boyers are famous for having intermittent stator coil pickup wires.

I just hate the annoying rough smudges in otherwise polished smooth running engine.
1. Switch spark plugs or replace a few news ones as even new ones can be bad.
2. Low rpm tends to jiggle bad conductions at a rate humans can tell while hi rpm can make-break bad connective too fast to detect the drop outs by human senses along. As noted think hidden copper breakage.
3, If you have NOT replaced the Boyer trigger terminal leads by an upgrade such as sold by Greg Fuath on this list - then you are wasting rough running time.
4. Not likely but possible the low rpm vacuum is not enough to suck gaskets up nice but hi rpm is. I'd had one side run rough down low but fine on throttle till I found a gasket hanging down on bad side with a carb bolt missing. But not on single carb.

hobot

I'm a bit confused on the focus here upon the EI. Boyer, like other EI systems, is a wasted spark system where the coils are driven from a common module output. It doesn't appear possible for the EI to discriminate between LH and RH coils, wires, or plugs. This was demonstrated when acadian swapped the plug wires, to no effect. Assuming that the plugs were swapped as well, the problem appears to lie outside the electrical realm.

Like Hobot says, I think anyway, the Boyer with cracked wire(s) will run at higher, > 2500 rpm but will have a definite misfire at lower rpm. Also, like he says, you need to do the stator coil termination mod, whether that's the problem or not. There are two kinds of Boyers, those that have failed and those that are going to fail. I'm speaking of the stator plate pickup leads.

An obvious, but important point is to make sure you have plenty of slack in the ignition wires between the engine and the frame. The ones that go to the Boyer stator plate.

You've probably done this but just in case. Unplug HT leads at the plugs and swap them to the opposite plugs, if problem doesn't move to the other cylinder then remove the plugs and swap them over as well, if problem sticks with the same cylinder then it's not ignition. Randomly swapping parts from one side to other just adds to the confusion make sure you are systematic.

Other things worth considering
If you've got the wrong pilot/needle combination you could be fouling a plug. Try fitting platinum or iridium ones they are almost impossible to foul. this can be a big problem while you try to dial in carbs (still got a box of dead ones on the shelf).
Try running a feed direct from battery to Boyer bypassing the ignition and kill switches and make sure you're engine ground is good, if in doubt run one direct to battery.
Make sure your exhaust is OK, its unlikely but collapsed internals could screw up one cylinder.

rick in seattle said:

I'm a bit confused on the focus here upon the EI. Boyer, like other EI systems, is a wasted spark system where the coils are driven from a common module output. It doesn't appear possible for the EI to discriminate between LH and RH coils, wires, or plugs. This was demonstrated when acadian swapped the plug wires, to no effect. Assuming that the plugs were swapped as well, the problem appears to lie outside the electrical realm.

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My thoughts exactly, but with so much emphasis on Boyer faults... I thought I was missing something...

hobot said:

3, If you have NOT replaced the Boyer trigger terminal leads by an upgrade such as sold by Greg Fuath on this list - then you are wasting rough running time.
hobot

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tried a search but cannot find info on this mod....

Sheeze, non us know what is wrong with our own bikes till finding it and it takes a lot wrong for mechanical to cause drop outs, sticking valves, flat lobes,chips bouncing in valve seats > so what's left?
There is ~15% spark strength difference depending on plug electrode spark jump polarity. Electrons like to jump off sharp stuff better than blunt.
I and others have had spark plugs troubles enough not to go too much into it till those verified working as expected.
Air leaks in flanges or cable holes. Intermittent crap clogging float needle on 1 of dual carbs. Gasket pressure leak down tunnels.

Brit Iron Motto is if if runs like fueling, makes noises like fueling, then think electrics.

hobot

Brit Iron Motto is if if runs like fueling, makes noises like fueling, then think electrics.

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95% of carburetion/fuel problems are electrical.

Coil - running a dual output Dyna. Both plugs/wire have been swapped. Now my thought is if it's a coil fault both cylinders should be acting up with a single coil... correct? Am I missing something here? Should I try switching the positive/negative wires? Would it even make a difference?


When we were running a commando racing outfit we had a misfire after a few laps for an entire season . It did not do it in the paddock even when being revved to 5000 rpm or running for longer periods .The coil was a Dyna ,a yellow thing with dual exit .
Throw it away and try original ones ...if your misfire is gone you found it .If not go looking for the bit you threw away in the bushes
it is not a good idea to change too much in one go ,as you have found out
btw all my bikes have been running on Boyers ,and they got used not pampered, and i never had one fail.....
strange so many seem to fail on the forum.

Boy oh Boy did lynxnsu drop a Commando owners gem here!

If not go looking for the bit you threw away in the bushes

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What Must Always be Kept In Mind is Anything Can Cause Anything in a Commando
and each one can produce Identical Symptoms so tossing-testing one item as faulty may not seeming to a thing, so you put back it and fix all the rest but still no joy.

At INOA '04 MidOhio rally Ms Peel would start but not run after I put in Greg's upgrade Boyer trigger kit. I about killed myself all day kicking on broken foot then after dark 6-8 of some of the most famous Nortoneers tired in vain till 10 pm to find the problem that caused bike to rev up like backfiring dragster out its open pipe turn cherry red from head to pipe tip then stall. EVERY Time the Boyer timing was time light checked it showed 40-50 degee advance!!!!! Floored the whole team. No Matter how set prior it over advanced instantly.

Then I broke out the Doe's Urine Moonshine and after finding broken ground, fractured fuse ends, bad coil, fouled no spark plug, poor key contact, Rod Rayborn noticed a quiver in the trigger plate, popped it to find I'd double nuted the terminal bolts in sensable strongest back up way that fouled magnets on them.
Then she roared so loud with blue jets out the open 2-1 that whole camp site hit their horns and lungs telling us all where to go with me and Ms Peel.
So I'll never forget how good those 4 scary gulps of 'shine felt then and the day after, ahh.

Oh yeah only spare plugs around were Non R, so made my LED signals became fun syncopated timing lights following throttle rpm spark rates on L or R side as desired.

hobot

acadian said:

This has been a consistent gremlin, and I've gone through most of the usual suspects but I'm hoping that listing these items out will help solicit something I hadn't thought of yet, regardless of what I've tried, the problem remains only with the left hand cylinder:

Click to expand...

If misery loves company, then take comfort in that you're not alone. My 850 misfires at idle on the left cylinder. It started after a major rebuild that included head work and a new cam. After having replaced the entire ignition system and both carbs to no avail, I must conclude that a valve is not seating at low speeds. I've not done a leakdown test to prove/disprove that, but that's my gut feel. My misfire is intermittant and only at idle. In a last ditch effort I replaced my Boyer with a TriSpark ignition and managed to get reasonable idle speed stability even though the left side still goes chuff chuff.

One of these days I'll do a leakdown test - I suggest you do the same.