Lucas Rita

Hi All, I have lost the 2 screws holding the ballast resistor to the Rita unit, could anyone tell me the size & thread etc?

Thanks in advance, Paul.

Uh...you don't use a ballast resistor with a Lucas RITA. It connects directly to the 6V coils. Commando, right?

illf8ed said:

Uh...you don't use a ballast resistor with a Lucas RITA. It connects directly to the 6V coils. Commando, right?

Click to expand...

The early type RITA box (with ribbs) did come with a ballast resistor. Sorry Paul don't know the thread size though.

illf8ed said:

Uh...you don't use a ballast resistor with a Lucas RITA. It connects directly to the 6V coils. Commando, right?

Click to expand...

Not the AB5 box, no (which hayabusaman0's is I believe).

Screw thread? My first guess would be metric, my second guess would be BA, and my third guess would be BSF.

Or, contact the original Lucas RITA manufacturer, Mistral Engineering: http://www.hoppybikes.co.uk/moira.htm

L.A.B. said:

illf8ed said:

Uh...you don't use a ballast resistor with a Lucas RITA. It connects directly to the 6V coils. Commando, right?

Click to expand...

Not the AB5 box, no (which hayabusaman0's is I believe).

Screw thread? My first guess would be metric, my second guess would be BA, and my third guess would be BSF.

Or, contact the original Lucas RITA manufacturer, Mistral Engineering: http://www.hoppybikes.co.uk/moira.htm

Click to expand...

The RITA I'm using now on my '72 750 is the same model (not the same unit) I used on my '73 750 and installed 1984. How old is the previous RITA "with ribbs"?
I was thinking the original ballast resistor pack which uses BA thread screws. That's attached to the coil mounting plate, but disgardeed when converting to the RITA.

I've got one of the early amplifiers. I won't get a chance to measure the resistor screw until this weekend. I'll post when I do.

And for the history buffs, I'll post a picture of the amplifier.

As best as I can tell these are #4-48 machine screws 1/4 inch long. They are too short for my old eyes to be positive with the thread gauge, so it is possible they are #4-40.

In any event, I have two extra stainless screws like the ones in the picture. They are 3/16 long rather than 1/4 but there seems to be plenty of thread. PM me with your address if you want them.

I guess the screws found a good home, so I am hijacking the thread :wink:

I got an AB5 amplifier of the later type (p/n 48016B, made 1978) along with some Commando spares recently. In a recent email, electrical specialist Al Osborn adviced not to use it on a Mk3. Do others share his opinion - is the current pull really of such magnitude that sparks will be affected during e-starting? Obviously condition of the battery comes into play. Has anyone tried this setup on a Mk3?

Knut Sonsteby

I have not done any tests with the AB-5 box so I can not comment on it's application on a MKIII. But the AB11 box which I have done many repairs is ideal for the MKIII. The only down side for the AB11 is that it is SO energy hungry (at 98% dwell) that I decided not to persue the manufacture of an AB-11 replacement. I had it pretty much all designed and engineering sample done but I pulled the plug before a test batch was built.
I believe the original AB-11 was terminated due to the discontinuation of the ST BU941 transistor in a TO-3 package. They would have need a new design board and cast housing just to use the TO-220 package.

BA screws is my guess

Dave, when you say "many repairs", was that an AB11 quality issue, or were external factors involved? Thks, Bennie.

Based on my examination, for some period, the output transistor was the same one as used in the boyer. So both systems, for the same reason, if the coil wire falls off the plug you risk damage to the output transistor and after some time it finally fails from internal heat. The rita you could fix and the boyer being potted was pretty much done...I've only done 2-3 dozen so it is really not all that many. Running an ignition with the HV wire off the plug (open circuit) is pretty much neglegent abuse.
I had one guy's system fail from running a 1 ohm coil but it took over 15 years to die. I completely roasted a potted harley coil with my rita ( I forgot to shut it off overnight while mounted on the distributor machine) yet it still worked on a new coil!! :mrgreen:

Thank you. this is reassuring.
Was wondering if it would be wise to replace mine with a modern one, inspired by recent failure of 30 year old EI module on my R80. Not the same breed though, contrary to the RITA, the BMW one needs good contact with its heat sink (it sure heats up), but the transfer goo goes crumbly over the years.