Misfire Troubleshooting

EstuaryBoy said:

Nah..... wrong oil

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Must be the phenolic ball bearing I used as per Mr.Hemmings! Live'n Learn

Well chances are it either carb or electrical , try single for a ride and then dismiss if problem still there , try running both carbs as singles .... then you know for sure ...

Scout63 said:

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?

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Have not looked at it...but it is an emgo switch fresh two seasons ago. Wouldn't a general power fault show as both cylinders impacted, not just LH side?

Why not just swap the carbs over and see if the misfire moves with it?

You’ll have to file small flats on the flanges but that’s all I think.

Fast Eddie said:

Why not just swap the carbs over and see if the misfire moves with it?

You’ll have to file small flats on the flanges but that’s all I think.

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Have heard the ticklers interfere and of course you can't get to adjustment screws etc.

For a trail ride you not likely to need to fine tune the adjusters. I dunno about the ticklers though.

Fast Eddie said:

Why not just swap the carbs over and see if the misfire moves with it?

You’ll have to file small flats on the flanges but that’s all I think.

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The ticklers will not allow swapping.

maylar said:

The ticklers will not allow swapping.

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Bugger.

I‘d be getting that single carb manifold back on then. But I’d want to test both carbs.

If missfire stays on LH and it seems you have eliminated obvious electrical possibilities ,then I would enshure
a/ the floast needle is neither flooding nor causuing fuel starvation , vibration linked possibilities
b/ that you do not have a needle jet come unscrewed in its jet holder
c/ you have the right spraytubes a 105 jet seems very lean to me
d/ that the needle has not dropped through the clip , not alaways easy to spot and can give very strange and bewildering misfires.

New open pipes and better tight connection at header has resolved the left side chirpy chirp sounds. These pipes do sound very nice. Have new video....



Smoke now visible pretty much all the time from left side...white not black. Maybe just a tad from RH. I'm thinking smoke has increased since last video and tests. Misfiring still happening, you can detect it in video if volume is up high...occasional on LH. Took her out for about an hour, round town and a few runs on highway. Still getting the herky-jerks...mostly noted at lower steady state city street speeds...1,500-3,500 rpms easily felt. Tried running about half a spray can of Seafoam through both sides, just to see if it cleans up any valve build-ups. No big improvement (did get a few puffs of black upon restart after 5min soak period...to be expected). Letting her cool down and will check plug condition and likely work on tank removal for next steps....

Looks like blue/white smoke to me, so you know you are tearing some stuff apart to see what's going on. The fact that now the RH has a tiny bit of smoke too could be good or bad... IF your head drain back hole is clogged with some piece of crap/silicone/swarf, the intake valves could just be swimming in oil... You could poke that hole with a guitar string from the intake rocker cover probably...

I know that some people here have said before that you could remove the head oiling feed lines MOMENTARILY to see if the smoking stops which would help with your diagnosis, but I think you are looking at some disassembly either way.

Maybe do an oil change and check for some metalic particles and rip open the filter to see if there's any clue to some breakage happening inside the engine. I know it sucks to be at this point. I had a cam follower lose a pad while idling in my driveway. I knew that my bike was coming apart as soon as I heard the noise. I had it apart in a few hours and knew what I had to do to make it right. (call Jim Comstock!)

It could be as simple as a head gasket leak too...

That's just my opinion, maybe smarter people will say different

Based on thead's content and the video I'd be inclined to hop on and find some place where you could play in the upper end of the tach while applying high loads. Never ride-it-like-you-stole-it, not to inflict punishment, but to unleash the beast, let it talk to you. I'm sure you know what I mean.

Best.

Try using your single carb inlet manifold as a test
As pointed out you can test both carbs that way
To test for a loose /damaged seal you can block off the oil feed to the head and go for a short ride to see if it persists
Also if you take the inlet manifold off take a look at the inlet valve see if it's.oily

My plan is to pull the intake rocker cover, have look around, try pouring in a few mL's oil to see if it drains rapidly. At this point I'm pretty much resigned to pulling the head to do a proper inspection. Good for the Soul ;-)

I’m gonna go out on a limb here and say... I think you have more than one problem.

Yes, the plugs are a bit darker than ideal. But not to such an extent that oil burning would cause a misfire. The smoking exhausts also point to oil being burned, but again, not to the extent it would cause a misfire.

A sticking valve might cause a misfire / very poor running though. You could take the exhaust pipes off and have a look up in the ports with a torch to see if the ex valves look particularly carboned up.

It would be a heck of a shame to spend a load of time and money rebuilding the top end only to find it still has a misfire when you’ve done... that would NOT be good for the soul! So I’d definitely test out both carbs one at a time on your single carb manifold, before stripping the top end, if I were you.

It‘s kinda difficult to understand what someone means by ‘misfire’ or ‘herky jerky’ etc via text, but generally speaking, such dramatic misfire type scenarios are down to either carb or ign 99% of the time IMHO (we’re not looking at a race engine and megaphoneitis here).

Its interesting that your misfire is at certain revs. That could link to certain vibration frequencies. That was the case when my Boyer back plate terminals broke and I was convinced my issue was carb related! I know your chirpy chirp was the left hand cylinder, but that’s gone now and the misfire remains, you can‘t tell for sure when riding which side is misfiring. In fact, if it’s causing a pronounced ‘herky jerky’ I’d say it sounds like both cylinders are misfiring. So you COULD still have an ign issue.

And although your carbs have been sleeved etc, you COULD still have a carb issue. I don’t know how you ascertained the pilots are clear? If it was by inserting wire or similar then they should be clear provided you used the correct gauge wire and blew them out fully afterwards. However, if all you’ve done is squirt carb cleaner through, all you’ve ascertained is that they are not FULLY blocked. You have not ascertained absence of a partial blockage that could effect flow rates. FWIW I chased carb issues for a whole season once only to discover it was machining swarf in the pilot jet, swarf from having them bored and sleeved! As already mentioned by a previous poster, the best way to diagnose carb issues is to mark your twist grip, you can then ascertain whether or not the misfire is related to a particular throttle position, and therefore a particular carb circuit. Revs don’t tell you that, at 3,000 rpm you could be at 1/8 throttle, full throttle, or anything in between.

Sorry for waffling on so long (lockdown symptoms) but I’m just trying to say that I think you need to do more problem solving BEFORE stripping the top end.

All only IMHO of course.

Can you do a leakdown test?

When lost in woods in winter it best to retrace your steps in snow(even if you went in a circle , eventually you see daylight) , it appears your big turn was carb work over past winter .... not sure if miss was evident last fall before carb work , but would retrace all carb work step by step even if it the upteenth time , from the list it seems that what changed during off season , always best to make a change at a time , verify good performance and only then move on , was running good before should run well again unless something huge is being overlooked .....

I agree with Eddie
Before I had my motor rebored I had a hell of a lot more smoke coming out than that and never a misfire
Nearly every misfire I have ever had on any bike has been electrical
But we all know the old saying
Every ignition problem turns out to carburation and vice versa
The key is to check everything one at a time

Tornado said:

My plan is to pull the intake rocker cover, have look around, try pouring in a few mL's oil to see if it drains rapidly. At this point I'm pretty much resigned to pulling the head to do a proper inspection. Good for the Soul ;-)

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I think your time would be better spent by systematic elimination of carburettor and or electrical faults.. Agree with Fast Eddy the oil being burnt is not sufficient to cause a misfire.. I thought you had in fact had a swap over of coils plugs ht leads and caps and still the mf was LH. Wellin that case ,if electrical its a fault in a wire or a freak intermittent shorting..before the coil- supply side stuff so to speak. I would check the fuse holder they will with age have a kind of make and break effect though would expect that to be both sides... but to repeat a loose needle jet will give you these symptoms as would a dropped needle

maylar said:

Can you do a leakdown test?

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No facility to perform that unfortunately. No air compressor. Would need to take it to a shop.