more narrow case questions

elmofongo · Post by **elmofongo** » Wed May 30, 2007 3:44 pm

Greetings,
I have a Monza 250 narrow case project bike that has been dormant for a while and I am about to start working on it again. I have some basic questions regarding ignition and fuel system.

I think the bike has the 6V 60W alternator. I say that because I only see 2 wires (instead of 3) in the cable coming out of the left side of the engine. For some reason the 2 wires are not yellow (as depicted in all the wiring diagrams I have seen). Instead, one wire is black and the other white. Maybe the cable was replaced by the previous owner. My questions are:

I would like to know what modern 6-volt coil and regulator/recifier I can use on the bike.
Is it worth converting to 12 volts and is there an easy 12-volt conversion kit?
Is it worth putting the Dellorto UBF24 carb on it or should I buy a more reliable modern carb?

Thanks

-Adriano

eNnihilate · Post by **eNnihilate** » Wed May 30, 2007 8:00 pm

There's an interesting post regarding 12V conversions in this forum under the title "12 volt ignition conversion." I believe this is the link: http://www.bevelheaven.com/~BB/phpBB2/v ... .php?t=108

Nick · Post by **Nick** » Mon Jun 04, 2007 1:04 am

I converted my narrow case to 12V, but it didn't really affect the performance much, however it did improve the lighting. Strange that there's only two wires from the alternator. This indicates that someone has probably converted the stock 3-wire set-up to 2 wires, which means if you hook those two wires to a rectifier off a small Japanese bike (or one from an electronics store) it will probably put out 12V and will charge your battery just fine. The standard conversion from 6V to 12V involves joining two of the alternator wires into one, so someone has already done that on your bike. However, with the above setup, my bike tended to overcharge the battery, so I ordered an electronic rectifier from Syd's Cycles in Florida (others have them also) and now it charges perfectly with no need for a zener diode, etc.
Any Lucas 6 or 12V coil will fit the stock Duc coil bracket perfectly. I'm now running a 12V coil from a Triumph. Bike runs great. I run a sealed beam headlight from a car in place of the stock unit and a 12V bulb out back.

Wrap the stock carb in a plastic bag and keep for the day when someone wants to restore the bike and park it in their living room. If you want to ride the bike, find a good used/new Amal 26mm or Mikuni, etc.

elmofongo · Post by **elmofongo** » Thu Jun 07, 2007 3:28 pm

Hi Nick,
At this point I don't even know if I have athe magneto or alternator.
Is there a way to find out without having the engine running?
Note that the bike is not really wired, so I can't tell from the way it's wired.

Thanks

Adriano

Nick · Post by **Nick** » Wed Jun 13, 2007 12:30 am

Your bike probably has the alternator. As far as I know, only the Scrambler and Diana had the mag (Yes, I have one each of those, too.) If it will spark without using a battery, you've almost certainly got a magneto.
You're luckly that there's no wiring on your bike, as that will eliminate the temptation to use the very old stock wiring. Get an electronic rectifier from some Ducati single supplier (or electronics supply store), ask them for a simple wiring diagram, and make your own simple wiring loom using modern connectors (I have some super-trick Japanese connectors which are identical to those on modern Japanese bikes--very nice indeed!) If you want to use a keyed ignition switch, just order one from a general parts supplier, they're cheap. I just use a toggle switch.
Try and find a manual for the bike.

have fun

chimera · Post by **chimera** » Thu Jun 21, 2007 10:22 am

The early Monza has a 2-wire alternator. These are the "shoe" type coils. The later 4-pole alternators have 3 wires. Is your Monza a 4 speed? If so, it almost certainly has a 2 wire alternator. Look on: http://www.motoscrubs.com/Duc_Manuals/D ... a_1964.pdf
for the 2 wire alternator wiring diagram.