Jetting issue?

[Matt Hale]

FWIW I never used a strobe on the ignition on any of my Morinis, just set static timing to the mark. Likewise carbs were tuned (ahem) by ear or wires under the slides. I did change a couple of choke rubber discs. I think your carb problem might turn out to be ignition related. Even a badly set up carb should allow the engine to run badly at tick over.

Thanks Ming...I'm on aftermarket blue transducer ignition boxes which, to get the full advance do need ignition pick up (red in my case) to be in position retarded a bit to normal timing mark. I do hover between thinking the issue is ignition one day and then carb another! I agree it seems a bit unlikely a carb would be so bad you couldn't;t start a bike and then it ran so badly it went onto one cylinder when warm. Trouble is I have had the pick up checked on another bike and no problem so next thing is to replace the blue transducer ignition boxes which I installed due to thinking the old ones were producing a weak spark/no spark/ intermittent fault. I have had spark coil re coiled, there's no wobble on the alternator flywheel as far as I can see so I don't no what the issue is.
...I think I may have just talked my self into buying a new ignition system from Mdina Italia!- pickup and new transducers! Thanks again to all on this thread...

[Matt Hale]

Hi All
I have discovered I definitely have a weak/intermitent spark on rear cylinder. I've checked all wires to the related transducer and found nothing wrong- good earth, good connections on the green and red wires (both ends) good copper HT leads clipped and re attached to be sure.
When I do the OHMS check on green lead - kick it over - I get 250 OHMS on both transducers. Spark leaps at least 5mm on front cylinder so I think that despite not having 300 OHMS 250 is enough for a spark.
As I can't find any other electrical issues I have order a replacement blue transducer £26+ VAT incase that is the cause of the weak spark.
"GENUINE PIAGGIO CDI/ COIL- VESPA PX & T5" Ducati 32398

...One Q..To try to up the power coming to transducer coils in green wire should I remove/disconnect the kill switch? Maybe makes no difference but just don't want any power wasted on anything not absolutely non essential... does power go there related to green wire? ( I know this may be a silly Q but I have read on Tr e mezzo that when doing test where you disconnect the green wire from ignition switch it said also kill switch if you had the electric start model which I do...

[Ming]

Source coil resistance is only an approximate indication of the state of the coil, as said many times on other posts. If it is still the original winding its a definite suspect. Also the measurement is carried out with the coil disconnected and not kicked over.

[mbmm350s]

Matt,

Let's get ignition sorted first.

Ming is spot on there, the generator winding resistance absolute value is of little help if you don't know what it's manufactured value was. If you have had it professionally rewound then they would have given you a test report with the resistance value quoted. The majority of original windings fail to give sufficient voltage below 200 ohms.
The pickup is a two piece system did you check both the red base and the rotor and that the rotor and pickup are compatible.
The rear cylinder is always most likely to have a weak spark, I described this phenomenon in ATG, and this was the reason for the redesign of the red pickup.
Pickup earths and their connections must be cleaned and good as the currents are small.
Normally 5mm in air is taken so that a 0.7mm gap can be jumped in a regime of 11:1 compression, however what you can't tell is that the spark is jumping inside the engine, here an inline strobe is useful.

You should disconnect the kill switch.

As you say wear in the carb won't prevent starting, but your post was about a sooty plug, now if it's difficult to start we are more inclined to be suspicious of the ignition .
Usually the blue scooter transducers need the pickup to be rotated so the arrow normally around centre of the housing mark which is the static mark referred to by Ming, moves about 6-7mm downwards, I.e anti clockwise as the engine runs anti clockwise viewed from this side I suggest you start with it like that.
There is a picture of the position in another post

The slide looks good.
The needle looks corroded.

Try to buy the transducers from a reputable Scooter shop, who have some skin in the game, I use Beedspeed there's Wasp performance too, they won't sell you fake copies, you could get jets from them too.
And their racing scooters will see off most air cooled Morinis

All the best
Mark

[Matt Hale]

Source coil resistance is only an approximate indication of the state of the coil, as said many times on other posts. If it is still the original winding its a definite suspect. Also the measurement is carried out with the coil disconnected and not kicked over.

Hi Ming- thanks for you reply- I was measuring at the transducer ends of the green wire to see what they received from the generator- the generator coil was rewound professionally not long ago so should be fine. I am also referring to Mark's latest post here...Many thanks again..Matt

[Matt Hale]

Matt,

Let's get ignition sorted first.

Ming is spot on there, the generator winding resistance absolute value is of little help if you don't know what it's manufactured value was. If you have had it professionally rewound then they would have given you a test report with the resistance value quoted. The majority of original windings fail to give sufficient voltage below 200 ohms.
The pickup is a two piece system did you check both the red base and the rotor and that the rotor and pickup are compatible.
The rear cylinder is always most likely to have a weak spark, I described this phenomenon in ATG, and this was the reason for the redesign of the red pickup.
Pickup earths and their connections must be cleaned and good as the currents are small.
Normally 5mm in air is taken so that a 0.7mm gap can be jumped in a regime of 11:1 compression, however what you can't tell is that the spark is jumping inside the engine, here an inline strobe is useful.

You should disconnect the kill switch.

As you say wear in the carb won't prevent starting, but your post was about a sooty plug, now if it's difficult to start we are more inclined to be suspicious of the ignition .
Usually the blue scooter transducers need the pickup to be rotated so the arrow normally around centre of the housing mark which is the static mark referred to by Ming, moves about 6-7mm downwards, I.e anti clockwise as the engine runs anti clockwise viewed from this side I suggest you start with it like that.
There is a picture of the position in another post

The slide looks good.
The needle looks corroded.

Try to buy the transducers from a reputable Scooter shop, who have some skin in the game, I use Beedspeed there's Wasp performance too, they won't sell you fake copies, you could get jets from them too.
And their racing scooters will see off most air cooled Morinis

All the best
Mark

Thanks for your generous reply again!
The red pickup rotar and magnet were sent to George Lane to be tested on a bike of his and came back as all fine.
I will disconnect the kill switch, replace the atomisers and E17 needles- glad the slide looks OK...I have ordered a replacement blue transducer from a reputable company I think- PEDPARTS <https://www.pedparts.co.uk> To get full advance using a strobe I have the timing adjusted retarded as compared to original standard position as you describe but when I put new transducer on, if bike starts OK, I will re strobe.
The parti of your reply I don't really follow is " Normally 5mm in air is taken so that a 0.7mm gap can be jumped in a regime of 11:1 compression, however what you can't tell is that the spark is jumping inside the engine, here an inline strobe is useful". Is this 5mm between the red pickup and the magnet?
One thing I was going to mention is that when I set the red pickup by tightening the small Allen bolts there is some movement backwards and forwards if I push on one side as I face the pick up. IE. it can rock a little. What I do push gently on the left as I tighten both Allen bolts equally until firm but not over tight...could this rocking movement and possible difference in set position cause issues? Ie each time I set in position and tighten the pickup might be slightly wonky relative to the magnet?

[mbmm350s]

Hi Matt,
In normal dry air the spark gap that a normal ignition system will jump is at least 5mm, that is why we bare the end of a lead and check. This is a standard check.
The voltage required to jump a gap inside an engine, indeed any space where air is compressed increases with compression ratio. The higher the compression the higher the voltage needed. However even though you might get a spark to jump 5mm in air it doesn't prove that the plug is firing, there are ways to check, the simplest is an inline strobe gun.

The oil seal behind the pickup is not seated correctly, it needs to be pushed further in, the proper depth is quoted in the blue manual. This stops the pickup from seating correctly. The magnetic rotor must not contact the pickup as it rotates because the air gap is important for the correct operation and the air gap should be the same all the way round.
Cheers Mark

[Matt Hale]

Hi Matt,
In normal dry air the spark gap that a normal ignition system will jump is at least 5mm, that is why we bare the end of a lead and check. This is a standard check.
The voltage required to jump a gap inside an engine, indeed any space where air is compressed increases with compression ratio. The higher the compression the higher the voltage needed. However even though you might get a spark to jump 5mm in air it doesn't prove that the plug is firing, there are ways to check, the simplest is an inline strobe gun.

The oil seal behind the pickup is not seated correctly, it needs to be pushed further in, the proper depth is quoted in the blue manual. This stops the pickup from seating correctly. The magnetic rotor must not contact the pickup as it rotates because the air gap is important for the correct operation and the air gap should be the same all the way round.
Cheers Mark

Hi Mark
Thanks again- I'll check the oil seal behind the pickup is flush and the air gap all around between the magnet and the pickup. This may well be the issue..I feel it isn't currently...I don't think I got a report with my rewound generator coil (spark coil) output when it was rewound but was done by a West Country Windings so I think it is probably all good. I am unsure how to do an inline strobe to see if plug sparking in cylinder....

[3potjohn]

On p80 of the Blue book is a statement and diagram concerning correct depth for oil seals. It is my understanding therefore that they should be inserted to that depth (2mm).
I was not aware of this for some time. It would be useful to get another view.
On airhead engines one has to be careful to install the rear crankshaft seal for example so that it matches the wear mark if there is one.
Having something to protect the seals when refitting the cases is beneficial by the way, though not relevant for you now. I never have had anything previously but mashed a seal last time so learned something.

[Matt Hale]

On p80 of the Blue book is a statement and diagram concerning correct depth for oil seals. It is my understanding therefore that they should be inserted to that depth (2mm).
I was not aware of this for some time. It would be useful to get another view.
On airhead engines one has to be careful to install the rear crankshaft seal for example so that it matches the wear mark if there is one.
Having something to protect the seals when refitting the cases is beneficial by the way, though not relevant for you now. I never have had anything previously but mashed a seal last time so learned something.

Thanks John- so deeper than flush. I still have to take a look and see how the oil seal is yet...hopefully it's back far enough nt to be causing issues with the pickup...Matt

[mbmm350s]

Hi Matt,
You said that the pickup didnt sit flat, so we assumed that the cause is that the inner spigot of the pickup is contacting the the face of the oil seal,
if this isn't the case then I don't understand.

Please ensure that the oil seal is fitted as per the workshop manual as John says, also the pickup should not contact it. You should not need to remove the seal, just push it further in as needed and measure with vernier to get the depth correct. You will need a suitable drift (hollow in your case) to push the seal further in. Unfortunately there is no positive stop for this seal so you will need to be careful to get it right.
John's point about wear is relevant there is usually a witness mark on the camshaft where the seal was - but you wont be able to see it.
Please make sure to use the large o.d washers, spring washer, and screws of the correct length as per the parts diagram to avoid stressing the pickup and there is no need to tighten excessively.

Cheers Mark

[Matt Hale]

FWIW I never used a strobe on the ignition on any of my Morinis, just set static timing to the mark. Likewise carbs were tuned (ahem) by ear or wires under the slides. I did change a couple of choke rubber discs. I think your carb problem might turn out to be ignition related. Even a badly set up carb should allow the engine to run badly at tick over.

Thanks Ming- I agree- not carb issue. UPDATE: The latest is I have good sparks now but when caps and plugs are on leads it looks weak. I await new spark plugs...I am currently also trying a replacement pickup magnet and black pickup ( I had the 2nd generation red). I have added transducers in the pickup red wires as I am using blue transducer boxes. The spark generator alternator magnet, on the opposite side of the crank to the pickup, can hold a heavy spanner so I believe is good (It was re magnetised a year or so ago) and the spark coil has also been professionally re wound.

[Matt Hale]

Hi Matt,
You said that the pickup didnt sit flat, so we assumed that the cause is that the inner spigot of the pickup is contacting the the face of the oil seal,
if this isn't the case then I don't understand.

Please ensure that the oil seal is fitted as per the workshop manual as John says, also the pickup should not contact it. You should not need to remove the seal, just push it further in as needed and measure with vernier to get the depth correct. You will need a suitable drift (hollow in your case) to push the seal further in. Unfortunately there is no positive stop for this seal so you will need to be careful to get it right.
John's point about wear is relevant there is usually a witness mark on the camshaft where the seal was - but you wont be able to see it.
Please make sure to use the large o.d washers, spring washer, and screws of the correct length as per the parts diagram to avoid stressing the pickup and there is no need to tighten excessively.

Cheers Mark

Hi Mark- Thanks for your reply- The oil seal behind my pickup is set back well so plenty of room for pickup to go into that recess. I use correct bolts and washers as described for the pickup. The latest is I have good sparks now but when caps and plugs are on the leads spark looks weak. I await new spark plugs...they may have been damaged when I rode last and ended up on one cylinder only and rough running...I am currently also trying a replacement pickup magnet and black pickup I had the 2nd generation red on and it may be OK). With teh black pickupI have added transducers in the pickup red wires- I am using blue transducer boxes. The spark generator alternator magnet, on the opposite side of the crank to the pickup, can hold a heavy spanner so I believe is good (It was re magnetised a year or so ago) and the spark coil has also been professionally re wound. I will update again and remain grateful for all advice received - Cheers - Matt

[72degrees]

An equally weak spark on both cylinders sounds more like low output from the ignition winding on the stator. Forget the resistance, see if you can measure how many volts AC it is pushing out at kickstart speed.

Until you are sure of that, don't spend anything on other components. I run the 'NLM' module with conventional coils and an OEM red type II pickup on my 2C/375. It may not be as clever as the Sachs system but "it works for me".

[Matt Hale]

An equally weak spark on both cylinders sounds more like low output from the ignition winding on the stator. Forget the resistance, see if you can measure how many volts AC it is pushing out at kickstart speed.

Until you are sure of that, don't spend anything on other components. I run the 'NLM' module with conventional coils and an OEM red type II pickup on my 2C/375. It may not be as clever as the Sachs system but "it works for me".

Hi - thanks for your reply above..I have been off bike maintenance due to work \hols so apologies for the delay getting back.
I have measured the AC voltage ( V~) on my multimeter with one probe in green wire from stator and other on earth. I get 26.00 max when I kick it over. Is this the correct way to measure - is that figure low?
I think I have weak sparks...but I have already had ignition coil rewound once and a spanner will hang on the magneto magnet.
Hope to hear from anyone on this ! I am very close to giving up!