1966 Monza Jr. 160 Stator issues

[BabyDuc]

Hello all,

new to the board. could really use some help in sorting out some electrical issues on my 160. It is completely finished but is not running well. I will post a picture of the bike in the photos section. I believe my issue is the stator, but want to exhaust every possible option before finding a replacement. I have replaced points, condenser, and coil with the hopes that i did not need to open the engine and remove the flywheel (for which i will need to find a flywheel tool). Here is the situation. the bike itself is only producing about 2.5 volts when running, even at higher rpms. I have temporarily hooked up a small 6v battery to help her along, and with the support of that battery she runs great. Any suggestions on other options for getting more power from the original stator?

[BabyDuc]

Hi All,

I am still hoping that someone has some ideas for me. Adding some additional detail just in case it can help to troubleshoot. I can run the bike at total loss off a small 6v battery and it runs great! But when I try to run it off the internal stator electronics, it will not run properly. I have measured each of the 3 wires coming out of the engine while the coil is powered by the battery only, and this is what i found. White wire produces about 4.5 volts, Yellow wire produces about 5-6 volts, and the Red wire produces about 11volts. I would have thought that any of these would have been sufficient since the battery is running at exactly 6volts, but if I switch from battery to stator while the bike is running and then disconnect the battery, the bike stumbles and dies.

Any suggestions or help is appreciated.

[double diamond]

I have no specific experience with 160’s but their ignition systems are similar, if not the same, as other Ducati singles, so here are a few thoughts. The AC ignition system (using no battery) requires that the flywheel be timed such that the sine wave of the current from the ignition coil peaks as the points open at full advance. If your 160 was previously run with a battery as the power source for the ignition, the flywheel may not be timed correctly for magneto ignition. The point cam on the advance unit is different depending upon whether it’s a battery/coil ignition or AC ignition. Same with the ignition high tension coil (i.e. the coil that the spark plug lead is attached to, not the generating coil); they are specific to the dwell of the point cam (green tag for AC ignition, red tag for battery). If your 160 runs well with a battery, it’s probably set up to run battery ignition. There are many posts on this site about the distinctions between the magneto ignition and the battery ignition. Try some searches on ignition systems and you’ll find all the information you need. Matt

[ducwiz]

Hi,

afaik the 160 Monza jr. has a magneto ignition, which is clearly visible in the circuit schematics:



Unfortunately, the points and condenser are missing in the schematic. They should be connected at point "R" (= italian "ruttore"). The colors of the stator wires are marked with numbers. The ignition coil must be a special AC type, a standard coil for DC/points ignition (battery powerded) will give you trouble. The old coils came with red or green labels, marking AC or DC type. But I can't remember the assignment of type and color ... please do a forum search on that topic.
On the other hand, you possibly converted your system to DC? If it still were the original AC system, your added battery would have no effect (if the wire harness is connected according to the schematic above).
Your voltage measurements are somewhat mysterious. Have you measured each wire against ground/chassis? And are the values measured at open wires, and by a AC voltmeter?

cheers Hans

[BabyDuc]

Thank you both for the replies. Based on everything I know of the bike (which is very little because it was purchased as a non-running basket case after the Previous owner passed away), I do not think this bike ever had a battery. I added the battery to power the coil to see if I had an electrical issue or if I had other engine issues. Since it runs great with the battery, I believe I have narrowed it down to an electrical issue.

Hans, your post is very intriguing because when I was troubleshooting, I replaced the points, condenser AND the coil. The coil I used was an aftermarket 6v coil. Based on your comment that they are different between an AC coil and a DC coil could this be my issue? (and thank you for sharing that, I had no idea there was a difference!). It runs perfect on DC current from the battery with the aftermarket coil, but as soon as I try it with the Stator’s AC current, it is not a happy bike. So maybe the Coil is my issue. If the aftermarket coil is a DC coil (most likely), then maybe that is not working when I switch to AC from the Stator? I do have the old coil and may try to swap that and see if that produces any improvement.

As for my voltage measurements, they were taken against chassis ground. I found them to be very strange as I thought the red wire was to the Stator ground and should have read “0”? I am far from an electrical specialist, so I appreciate you bearing with a novice.

[Jordan]

If your original coil is faulty, something like this might work:
Ebay item 381858268791

[double diamond]

If you search this site for the terms “AA367B” or “green label” you will find a great deal of information on your ignition system. Matt

[BabyDuc]

Hi Jordan,

the EMGO coil that i used is Ebay item number 201269739628. that is not the same one that you suggested. is the one i purchased clearly a "no-go" or do you have any thoughts on it?

[Jordan]

The coil shown looks like a DC type, as used with a battery.
I don't think the stated secondary resistance of 9.47 ohms is correct. It's usually in the thousands, but that's by the by.
The suggestion is to try an AC type coil.

[ducwiz]

Some guy published his resistance measurements on both coil types in the ducati.ms forum:

AC and DC coil pin 1 to pin 15 (primary to ground) resistance is 2-4 Ohms

AC coil: primary to secondary coil (pin 15 to plug wire pin) (9K ohms)
DC coil: primary to secondary coil (pin 15 to plug wire pin) (6K ohms)

This indicates that the AC coil has a higher turns ratio, i. e. the DC coil will produce less high-voltage for the spark when used in an AC/magneto system.

Btw, the DC coil has definitely the red label, while the AC type is green.
A source in the UK for both coils: http://www.classicducati.com/index.php?page=6&act=viewCat&catId=5

Hans