Timing Strobe Help!

[PPuxley]

I went up to Electrex World which is just up the road at Stoke Row, to pick up a pick-up.
They sell a replacement for Ducati kokasan for £36.
https://www.electrexworld.co.uk/cgi-...2ehtml#SID=403

I had a long chat with one of the techs about the issues I was having and his view was that it was highly unlikely to be the pick up coil.
"They either work or they dont"
On the subject of coil impedance, he said it wasnt the coil impedance that was critical, but its inductance, and inductance can be achieved by various combinations of winding thickness and turns, hence why coils of different resistance may still work.
OEM resistance is 100 ohms, whereas these replacements are 460 ohms.

The upshot of the conversation is that only leaves the vertical carb as the culprit having swopped everything else (and it being unlikely to be the pick up.)
So the carbs will be coming off again tomorrow for another really good look in the LH one.

And hopefully another trip to Electrex World to return the pick up unopened.

[Davy]

So so close patrick Got to admire your perseverance, which I’m sure will pay off. Did you try another set of carbs out of curiosity.

[PPuxley]

Originally Posted by Davy

So so close patrick Got to admire your perseverance, which I’m sure will pay off. Did you try another set of carbs out of curiosity.

Not yet! but Ive just been talking to a local mate that has a set that he replaced because he obtained another set at a good price. So even if his old set are not right, just replacing my vertical one with something different, and seeing a change......or not, will indicate whether my carb is the problem.....or not.

[jerry]

problem is Patrick im having similar problems with the M750 and for months i was convinced it was the carb ,, but thats Definitely not my issue , the carb works fine on other bike ,, its now looking definitely as an ignition timing issue ,, pickups are testing fine at 100 ohm and the coils and ignighters are fine ,, so Im still baffled bike runs but really crappy no air leaks or mechanical issues .

[PPuxley]

Originally Posted by jerry

problem is Patrick im having similar problems with the M750 and for months i was convinced it was the carb , but thats definitely not my issue , the carb works fine on other bike ,, its now looking definitely as an ignition timing issue ,, pickups are testing fine at 100 ohm and the coils and ignighters are fine ,, so Im still baffled bike runs but really crappy no air leaks or mechanical issues .

OK, Jerry, some progress this morning I think or confirmation of something I had found already
Agree, I dont think its the carb.
This morning I borrowed a Gunsons colourtune.
When used on the vertical cylinder I get a good colour at idle, but as soon as I raise the revs the spark stops (no colour)
This confirms exactly what I get when I try to use the strobe on the vertical cylinder- the strobe stops working above idle.
So it is definitely a breakdown that is causing no spark at anything above idle........but why????
Ive swopped coils and leads and ignition units between the cylinders and the fault remains always on the vertical.
By a process of elimination that leaves the only unchanged things, the Pick up coils and the low tension wiring to the coils and ignition units. BTW my coils and pick ups test fine for resistance, like yours.
So despite being told its unlikely to be the pick up coils ("They either work or they dont"), I think thats where Ive got to go next.
But, Jerry have you done anything with your pick up coils that would scotch this idea?

[jerry]

No I have not done anything , to the pickups ,, i think I may buy one or 2 just for ,,er peace of mind or desperation ha ha ,,I am borrowing a strobe from a mate to see if its out of synch ???? I also have a colortune ,, but they can be awkward to understand what one is seeing

Originally Posted by PPuxley

OK, Jerry, some progress this morning I think or confirmation of something I had found already
Agree, I dont think its the carb.
This morning I borrowed a Gunsons colourtune.
When used on the vertical cylinder I get a good colour at idle, but as soon as I raise the revs the spark stops (no colour)
This confirms exactly what I get when I try to use the strobe on the vertical cylinder- the strobe stops working above idle.
So it is definitely a breakdown that is causing no spark at anything above idle........but why????
Ive swopped coils and leads and ignition units between the cylinders and the fault remains always on the vertical.
By a process of elimination that leaves the only unchanged things, the Pick up coils and the low tension wiring to the coils and ignition units. BTW my coils and pick ups test fine for resistance, like yours.
So despite being told its unlikely to be the pick up coils ("They either work or they dont"), I think thats where Ive got to go next.
But, Jerry have you done anything with your pick up coils that would scotch this idea?

[PPuxley]

Originally Posted by jerry

No I have not done anything , to the pickups ,, i think I may buy one or 2 just for ,,er peace of mind or desperation ha ha ,,I am borrowing a strobe from a mate to see if its out of synch ???? I also have a colortune ,, but they can be awkward to understand what one is seeing

The colourtune for simply seeing the spark fail on the rear cylinder is very straightforward, it just goes blank. It was flashing at idle then when the revs are raised.....Nothing. Quite clearly showing no spark.

If you are getting new pick ups, you can get them from Electrex World £36 each Type P08. 460 ohms.
Or with a bit of modification Brads suggestion Yamaha CY-7, 200 ohms

But you might as well wait till Ive tried!

[Mr Gazza]

Despite what you have been told by an expert, pickups and also crankshaft position sensors do fail intermittently. This is usually brought on by rising heat. After the engine has cooled down the sensor/pickup will function again.
Yours is not a heating problem, but rather affected by increasing revs. In my mind I don't see why a weak pickup would fail to see the trigger as it sped up.

I know that it interrupts a field, but not what is producing the field. If it is the sensor then replacing it should restore the field, but if it is the trigger, then that should be suspected.. Unless of course the trigger is common to both pickups?

A high resistance connection somewhere in line between the pickup and igniter might cause this problem, especially if the current decreases with revolutions.
Or maybe just the subtle increase in vibration could jiggle a connection out of contact?

I'm sure that the pulse from the pickup is quite a low current? So wouldn't put up with much interference?

[PPuxley]

I think I have just elimanted the coil low tension wiring
I swopped the pick up wires between the ignition units and swopped the HT leads front to back
Fault remained on the back/vertical cylinder.

[jerry]

vertigo !!!!???? ha ha im ust more confued than ever ,, but Patrick and me can try and co-op on this ,, It was made by Italians so we should be able to sort it out ,,'' in vino veritas[''

[PPuxley]

I wont break open the champagne yet, but I think I may have solved the issue! I need to balance tune and road test yet.

This morning I installed a new pick up coil for the vertical cylinder.

On start up with the colourtune in place on the vertical I was immediately able to see it was receiving a spark and firing throughout the rev range. I then set up the strobe and again I was now able to see the strobe working at all engine speeds, I was also now able to confirm that the dynamic timing was spot on at both idle and revs.

So it would appear that it was indeed my vertical pick up coil that was causing the issue. Inspite of inspecting the old coil carefully I could see no fault on it , let alone a fault that might only develop at speed.

In summary, for a fault on firing of a single cylinder, it is relatively easy to swop coils, HT leads, plugs, LT wiring to see if the fault changes cylinder. A fault in the carb or pick up does involve a bit more dismantling and rework effort. The fault can be made all the more opaque by apparently seeing the correct resistance in what turned out to be a faulty pick up coil.

I would also now recommend using a Colourtune, (not necessarily as a quantative analysis tool for tuning), but theres nothing like being able to physically see into the firing (or in my case, non firing ) chamber. Although the non working strobe at revs was indicating the same thing the colourtune let you physically see the spark stop working as the revs were raised.

So it may be axiomatic that you find the fault in the last place you look........but its always a shame when its the last place you COULD look rather than the first!

[Mr Gazza]

Eureka!
It was screaming pickup to me, but it doesn't help when people tell you that pickups either work or don't work.
So what we have learned here is that not only can a pickup failure manifest when it gets above a certain temperature, but also when engine revolutions exceed a very low threshold.
This proves that they can work just a little bit, but not enough!

I'm delighted you've cracked it and without mauling the carbs too.
You only ever find what you're looking for in the last place you look unless you insist on continuing to look after you've found it..

[Darren69]

Originally Posted by Mr Gazza

Eureka!
It was screaming pickup to me, but it doesn't help when people tell you that pickups either work or don't work.
So what we have learned here is that not only can a pickup failure manifest when it gets above a certain temperature, but also when engine revolutions exceed a very low threshold.
This proves that they can work just a little bit, but not enough!

I'm delighted you've cracked it and without mauling the carbs too.
You only ever find what you're looking for in the last place you look unless you insist on continuing to look after you've found it..

I very nearly commented on the pickup issue as from my experience that wasn't entirely true. Coils can behave differently or oddly if there is internal corrosion and can break down under certain conditions, as you have found. Same for HT coils or coil sticks as I found. So that was unhelpful comments from Electrex. Glad you got it sorted in time for a few weeks of fun.

[PPuxley]

Originally Posted by Mr Gazza

Eureka!
So what we have learned here is that not only can a pickup failure manifest when it gets above a certain temperature, but also when engine revolutions exceed a very low threshold.

And possible the other way round. We will know when Jerry has a go at swopping his out, because his fails at low revs and then comes in as the revs are raised.

Just taken it for a spin up the lane , less than a mile round trip.
Well, thats better! When I said it was running a bit flat before, it certainly was, I was riding a 450 single dragging another dead 450 around!! Just a tad crisper now

Weather looking a bit grim here so thats it for today. Thank you for all your input.

But here are the requested piccies of the finished article (which have actually been posted already on the build blog)

Album

[Darkness]

Yay!


(It’s obvious now you’ve found it)