Misfire Troubleshooting

Headed out to parkade to have go at a few more items (direct battery positive to head/EI; swapping silencers....)....assuming to God of Laziness has been full appeased!

not sure if coils are new , I see you have swapped wires , is there any possibility the coils may have been over tightened in the past , is mis-fire constant at all temps , do you notice the miss first thing from first cold start of day .... patience is key

RoadScholar said:

I'm surprised that someone hasn't suggested swapping the coils, if you haven't tried that you may want to consider the maneuver.

You have 150 PSI measured from both cylinders so the wrist pin circlip idea seem pretty remote and would produce consistent symptoms, and if one of your cylinders did have a score you would expect an oily (more oily) plug in that cylinder and measurably less compression.

A bad ground, IMO, is a possibility that you can rule in or out quickly by simply employing some alligator clips nand jumping the engine to the coil bracket and the engine to the the battery.

If the pictures of the plugs were taken after the engine was idled for more than 30 seconds the data is not worth considering.

Did you replace the needle jets and the needles when you got the carbs back from sleeving? Did you sync them?

I like a bad coil or a poor ground loop. Don't go looking too deep or someone will come along and suggest that your drive side layshaft bearing caused similar symptoms...

Best.

Click to expand...

It's your drive side layshaft bearing.

So, you're at the cross roads with a lot of guessing where the final address is located. Maybe you can take a single step in the right direction and eliminate half of the possible wrong turns.

So,... black smoking is a rich fuel condition. Bluish/white smoking is burning oil. You should observe carefully the smoking you have witnessed and make a determination on which direction you should go. Are you chasing some fuel richness issue or burning oil issue? Figuring out which kind of smoke can eliminate half the guessing.

If it's rich fuel situation you have certain things that richness points to and certain things that richness rules out:
Carb assembly, correctness of parts, and their settings are indicated as possibilities. An air leak is not indicated because an air leak would cause a lean condition. Weak spark is a possibility, but it's only on one side in a wasted spark system, so it should be easy to check that possibility by switching components from one side to the other and expect the miss to switch sides with the bad component. Maybe your LH float is hanging up and flooding the LH side.

If it's oil fouling there's a few possibilities:
Maybe the rocker spindle oil hole drilling is in pointing the wrong way on the LH side. Maybe the LH intake valve seal has broken. Maybe the valve guide fit is sloppy and oil is getting by the guide. Maybe the head's rear drain hole is clogged so the head is swimming in oil on the intake side of the head (but that wouldn't explain why the RH side isn't oiling too). Maybe it's a head gasket leak from the pushrod tunnels. If it was the displaced circlip as I mentioned earlier, you would have a lot more smoke and it would increase as you keep on using the bike.

If it's an issue with oil, you are taking some stuff apart, so might as well start with the least intrusive first. Take the valve covers off and see if there's a pool of oil unable to drain through the drain hole which might be clogged.(poke it with a wire...) Then inspect that the intake valve seals are in place. Maybe undo the rocker spindle cover and check that the spindle oil port is pointing the correct direction. Lastly, maybe you have a head gasket leak at the pushrod tunnel. You could try a retorque of the head to see if the miss goes away.

BTW, good post with the list. Personally, I think it's oil fouling.... just my gut from looking at the plugs

Smoke seen yesterday definitely light/grey to white. Not black sooty.

Opened silencers now fitted. Heck of job getting some of the studs out the muted set....ultimately propane needed on the stud mount shoulder...someone likely used locktite red. Muted pipes had what best describes as a faint maraca sound when shaken...a like a bit of sand inside that could not be shaken out. Felt fair bit heavier than the open set now on. Must be all that epa regs beating sound proofing within ;-)
Noted LH side silencer clamp could not be tightened sufficiently to grip header firmly. I had found some leakage at that joint previous when spraying WD40 at the joint....as it smoked up from heat, could see puffs from joint. Gave it all the clamping force it could take but never got it fully sealed. Luckily, open silencers came with pair of rough balanced header pipes with clamps and one of those clamps worked well on bike.

Haven't fire up yet...maybe before too late tonight or when weather is drier outside tomorrow.
As for direct ground line to battery, have to await tank removal....God of laziness needs worshipping.

Craig said:

not sure if coils are new , I see you have swapped wires , is there any possibility the coils may have been over tightened in the past , is mis-fire constant at all temps , do you notice the miss first thing from first cold start of day .... patience is key

Click to expand...

Mis happens at first start and maintains through to full hot. I've ruled out coils via swapping plug ends left for right and right for left...issue remains on left.

may yrs ago in a province far and away from where you are i had a suzuki 750 that had an intermittent miss, as one of the plugs was not firing, turn out to be a bad cracked plug cap... may not apply but sharing another possible cause.. we are cheering for your success.

Tornado - have you checked your ignition switch for good ground and continuous contact? I think current flows from the battery through the switch to ei and your coils. Can you jump power from the battery to your ei power lead and see if it clears up?

Tornado said:

Swapped cables & plugs side to side...trouble stayed LH side.

Click to expand...

Tornado said:

3. Coils: Swapped left for right (by migrating plug ends left/right)...no change in issue, stayed LH side. This eliminates coils as the issue.

Click to expand...

To be clear, you at some point actually swapped the L and R leads themselves, not just the ends at the coils?

I had a new plug cap that was very high resistance that I found and had given that side a rich spark plug.

Putting a DMM across each of the caps/leads to measure total R should iminagre that difference.

Tornado said:

Smoke seen yesterday definitely light/grey to white. Not black sooty.

Opened silencers now fitted. Heck of job getting some of the studs out the muted set....ultimately propane needed on the stud mount shoulder...someone likely used locktite red. Muted pipes had what best describes as a faint maraca sound when shaken...a like a bit of sand inside that could not be shaken out. Felt fair bit heavier than the open set now on. Must be all that epa regs beating sound proofing within ;-)
Noted LH side silencer clamp could not be tightened sufficiently to grip header firmly. I had found some leakage at that joint previous when spraying WD40 at the joint....as it smoked up from heat, could see puffs from joint. Gave it all the clamping force it could take but never got it fully sealed. Luckily, open silencers came with pair of rough balanced header pipes with clamps and one of those clamps worked well on bike.

Haven't fire up yet...maybe before too late tonight or when weather is drier outside tomorrow.
As for direct ground line to battery, have to await tank removal....God of laziness needs worshipping.

Click to expand...

Right before our lockdown I went for a ride, and I had stopped to get gas, and a bit down the road I thought something was not quite right. Lost a bit of power and snap in the motor, had some popping on overrun, and thought it might be bad gas.

When I stopped again I saw the spring hanging from the header tang on my 2-1 pipe and the other end of the spring had snapped halfway at the end. So there was no tension on the silencer end of the header

So i made a bodge and took a pliers to the spring for the trip home, and it was back to running normally.

gortnipper said:

To be clear, you at some point actually swapped the L and R leads themselves, not just the ends at the coils?

I had a new plug cap that was very high resistance that I found and had given that side a rich spark plug.

Putting a DMM across each of the caps/leads to measure total R should iminagre that difference.

Click to expand...

I swapped plug ends of HT left/right, so LH coil fed RH plug, and vise versa. Issue stayed LH side. Later moved plugs left to right and still later tried different brands (to champion from ngk resistor type).
This should eliminate coils, leads, plugs, correct?

gortnipper said:

Right before our lockdown I went for a ride, and I had stopped to get gas, and a bit down the road I thought something was not quite right. Lost a bit of power and snap in the motor, had some popping on overrun, and thought it might be bad gas.

When I stopped again I saw the spring hanging from the header tang on my 2-1 pipe and the other end of the spring had snapped halfway at the end. So there was no tension on the silencer end of the header

So i made a bodge and took a pliers to the spring for the trip home, and it was back to running normally.

Click to expand...

So you're saying air leak at silencer joint can give trouble. That will be interesting to see at next fire up. Was thinking to use some sillycon sealant at joint but different clamp seems good.

Tornado said:

I swapped plug ends of HT left/right, so LH coil fed RH plug, and vise versa. Issue stayed LH side. Later moved plugs left to right and still later tried different brands (to champion from ngk resistor type).
This should eliminate coils, leads, plugs, correct?

Click to expand...

Yes. Sorry, somehow I read it as coil end swap. I guess I was visualizing more than reading...

Tornado said:

So you're saying air leak at silencer joint can give trouble. That will be interesting to see at next fire up. Was thinking to use some sillycon sealant at joint but different clamp seems good.

Click to expand...

Popping on overrun is quite common with slip on exhausts on Ducs. The Termis on mine do it a bit, but my 2EX1 never did until the spring broke.

Time to invest in a gremlin bell.

I can relate to your frustration.

One other thing not mentioned - do you run your Amal's with chokes - they're held open on tension so if one side is not rising properly it would impact the mixture (possible problem with the cable from the splitter box to the choke slide or the spring/guide).

I mention this because I spent a day chasing a dead cyclinder at the Spanish International Rally some years ago, I eventually discovered that the throttle cable (03.3145) ) had pulled through the splitter box so only one carb. slide was rising. I removed the chokes & used their splitter box for the throttle cables (I've not replaced the chokes!) & not had that problem since. The carbs, cables, splitter box etc. were all brand new & fitted a just few weeks before the rally.

Torontonian said:

It's your drive side layshaft bearing.

Click to expand...

Nah..... wrong oil

Although it seems a dead horse is getting flogged here .... got to ask if you suffered mis-fire when you were running the single Amal (if my memory is correct) as set up when you got bike .... maybe try fitting single carb to see what transpires , prolly mount carb from other side of miss , you just never know , as it seems you have ruled out electrical gremlin at work , hope you kept your manifold or maybe I’m suffering brain mis-fire and it always been dual carb .... may be worth a try ....

Mike Sullivan said:

I can relate to your frustration.

One other thing not mentioned - do you run your Amal's with chokes - they're held open on tension so if one side is not rising properly it would impact the mixture (possible problem with the cable from the splitter box to the choke slide or the spring/guide).

I mention this because I spent a day chasing a dead cyclinder at the Spanish International Rally some years ago, I eventually discovered that the throttle cable (03.3145) ) had pulled through the splitter box so only one carb. slide was rising. I removed the chokes & used their splitter box for the throttle cables (I've not replaced the chokes!) & not had that problem since. The carbs, cables, splitter box etc. were all brand new & fitted a just few weeks before the rally.

Click to expand...

No chokes fitted (as listed in the summary posted yesterday).

Craig said:

Although it seems a dead horse is getting flogged here .... got to ask if you suffered mis-fire when you were running the single Amal (if my memory is correct) as set up when you got bike .... maybe try fitting single carb to see what transpires , prolly mount carb from other side of miss , you just never know , as it seems you have ruled out electrical gremlin at work , hope you kept your manifold or maybe I’m suffering brain mis-fire and it always been dual carb .... may be worth a try ....

Click to expand...

No misfire like this when running single amal. All sorts of other issues but not this one, which has made riding unpleasant for only the past five or six outings, likely starting late last year, leading me to get resleeving done.
I have considered swapping back to single as a test. Would certainly narrow candidates considerably.
The LH carb was on bike when acquired and it gave me a fair bit of troubles with worn needle jet and clogged fuel passages, idle jet. Things were better after switching to RH carb, maybe it had less overall where. I'm fairly confident I've sorted all carb issues now though.