Thanks for the suggestion RT and Yamfan.

My strobe is in my toolbox at work and I will not be able to access it till monday.
It is no problem connecting it to an old 12v bike battery and testing the timing again with engine running.

I did carry out your suggestion RT and heated up the coils individually with the meter attached, they must have been over 100c, I could not touch them and even the crankcases themselves were approximating running temperature.

While the resistance continued rising, nothing went open line.

It may well not be ignition, but every fibre of my being tells me it is not fuel, the misfire was too harsh. It almost felt like the timing was going way over advanced.

The static timing was fine, the compression is fine, the fuel seems fine if slightly rich and this misfire has only appeared after a couple of hundred miles.
I will strip the carb again and put it in the ultrasonic cleaner at work.

Apex, I have not forgotten your input. Resting battery voltage after the ride is 6.49V and during the ride the indicators ect worked fine, even while braking. Nothing suggested a poor charge in the battery.

The CDI was a brand new OEM unit. I do know of a place that says they can test them. Maybe that is an option.

Only other fly in the ointment is the fact that due to the oil pump rebuild, I put 100 mls of two stroke directly into the 3/4 full fuel tank, just in case the rebuilt pump failed to deliver.
With the oddly worn cylinder, I am paranoid about lubrication. Another thing to worry about.

With the pump delivery going full blast and lots of oil in the fuel, would this cause a misfire?
The misfire did not sound like a weak condition and the misfire started, albeit not so clearcut and not so harshly before the oil was added.

The exhaust was not smoking excessively and the plug was dry, not oil fouled.

My head is melting. Too many spinning plates at once and nothing is clear cut.

To cap it all, with the tendons in my ankle bolloxed, I can't even put it back together and test ride it.
It might have simply been a bad ( but almost new) plug or the ignition coil, both of which have been changed.

I am sick of that soddin bike.

These things were sent to try us--& you by the sound of it.
No it won't be an oil problem in my opinion.
Hope ya able to record the sound or something eventually.
Just out of curiosity, you say the ohm kept climbing--so resistance went above the 450-ish i think you said.

True. It went around 500 before i lost my nerve and stopped heating. I did not want to start melting solder.


Hmm.  I used soft solder to attach the wires of the new stator harness I made..... Not silver solder.  Oh hell...

180c / 190c is the melting point of general soft solder. Would those coils get that hot when pulling a load?

Well, it is back together and running. Had it idling at 1300rpm for about half an hour, snapping the throttle open now and again while I bolted the tank and seat down and generally letting it get another heat cycle over with.

I left the generator cover off and will bring my strobe home tomorrow to check the spark advance.

Have to say that the new cylinder is almost silent at idle. The only rattle I am hearing at idle is the backlash in the transmission and primary gears.
It goes away completely with the clutch pulled in and you can barely hear any mechanical noise at all.

Still not able to test ride it yet, being off work all last week with tendonitis in my ankle, it would not be a good look if I were to injure myself riding a motorcycle.

Really got fingers crossed that it was the HT coil on the way out.

On a more positive note, it does make a pretty living room display.  I just hope that it will be more than that...

I like your new furniture I hope your wife likes it

Well I just had the strobe on it.  To my consternation it appeared to be running a little bit retarded.

The static timing mark was retarded and when revving it up, the full advance mark was only reaching half way to the mark on the stator...

Then I discovered it was me that was retarded. 

I had knocked the degree wheel on the strobe and set it about 3 degrees retarded. 

Set it back to zero and tried again.

Static timing line broadly in line with the stator line.  Revving it up, the full advance line lined up perfectly with the stator line.

There were no apparent spark outages and as said, it is advancing.  So CDI and wiring are out of the equation.

I put the equipment away and was about to get my riding gear and give it a test ride with the generator cover off to maximise airflow around the source coil windings.

As soon as I picked up my helmet, the usual result that has happened across an entire lifetime of motorcycling always happens whenever I pick up my helmet.
A big black cloud appeared and raindrops the size of 50p pieces started hitting the floor.

It is now angrily flashing lightning and grumbling away outside...

Test ride will have to wait.  I hope it was the HT coil going bad.

 

Roads dried out so I took it on my local run - about 15 miles of country lanes and local villages.
About 10 miles in, a threatening cloud appeared and I cut the run short by about 5 miles.

Run was conducted with the mag hanging out in the breeze and the plan was to refit the cover and test again.
Alas the clouds opened and the roads are sopping wet again.

Meantime I can report that the misfire up to now has gone.  Yay!

So it was a bad plug or a bad coil breaking down under load.  I have seen both display the same symptoms in the past.
Only thing I can say is coil had a fine line of rust where the laminated core entered the casing.
Whether this had penetrated inside and was allowing a path to ground under load, I dunno.

Without being able to view a graph of peak voltage in the system I just have to guess.

Nothing else changed apart from the above half throttle misfire.  Same power and responsiveness at below half throttle and still starts second kick after standing for a week and first kick if it has already been running that day.

Another test with cover fitted.  No misfire to press.  Of course, it being a new cylinder and piston I have not really gone above half throttle much.  Just enough to confirm it has gone.

An odd occurence is that the vibration that started at 5000 rpm is now at 4000 rpm.  It is not a heavy, knocking vibration, just a tingle through the bars and pegs. The misfire was far harsher.
When I let the revs creep up to 5000 in the lower gears (half throttle only) it seems to start to diminish.

Go on--i know ya want to rev the bollocks off it just to see.
I used to rebore mine & race it the next day with no issues.
Ok--don't follow me!!. I create all my own problems lol.

engine mount bolts still tight.