8 replies to this topic

[frog998]

Tried setting the timing in my mates car today and its not advancing when you rev the engine.
Its a mini mayfair 1982 with a metro 1275 engine and electronic points.
With the timing light set on no1 plug TDC when you rev the engine the light stays where it is rather then advance as expected, car also mis-fires when you floor the accelerator (assume to 2 are related)
What is the correct dizzy for a 1275? And is the timing still 5deg BTDC?

[dklawson]

The backfire/misfire probably are related to the lack of advance.

You can remove, disassemble, and service the advance mechanism. You are likely to find the bob weights are stuck on their pivots and not free to move. It's an easy fix and costs only time as opposed to buying a new dizzy.

I can't say what the correct dizzy would be for your application.

As for the timing, you can always go "by the book" based on the origin of the engine. OR, you can use the timing light to set your MAX advance (once the advance mechanism is working) to about 32 BTDC with the engine running at about 4000 RPM. Test drive the car after setting that timing. IF you hear any knocking or pinging, retard the timing about 2 degrees and repeat your test drive. Keep retarding the timing as necessary until you hear no spark knock when lugging the engine. That will be the optimum advance for your engine in its particular condition and for the fuel you are using.

[frog998]

Does anyone have an idiots guide to dissembling / cleaning the dizzy?
How are the weights attached?
This is about the 3rd or 4th dizzy my mate has had fitted by various local garages all gueesing and just changing parts for the sake of it and he's fed up of being told they have fixed the problem when they haven't

[Shifty]

If you get stuck I've got a dizzy that I know to be in good working order, its a later type electonic one.

If you like you can pop over and we can try it on the car?

[frog998]

If you get stuck I've got a dizzy that I know to be in good working order, its a later type electonic one.

If you like you can pop over and we can try it on the car?

Cheers, are you about tomorrow sometime?

[dklawson]

Even if you get the dizzy for Seamus, take the old one apart and see what's going on.

I don't have any dizzy disassembly instructions per-se. However, it's pretty obvious once you start at what's involved. A quick summary would be to unscrew and remove the electronics from the "breaker plate". Then remove the breaker plate. Once the plate is out, you'll be looking at the bob weights. The weights will be on little pins, typically with tiny circlips holding them in place. Springs will also be there to pull the parts back into their rest positions. Depending on the advance curve, the springs may be the same size or different. You need to remove a screw in the center of the dizzy shaft to remove the four-lobe cam. The screw may be hidden under a felt disk. With the screw removed you'll be able to extract the four-lobe cam. I believe it's hooked to the springs so you will need to unhook them prior to/as you remove the four-lobe cam.

The advance may not be working for three reasons I can think of.
1) Broken springs - so the dizzy is at full advance as soon as you start the engine.
2) Seized bob weights - rusted to their pivot pins.
3) Four-lobe cam stuck - the cam could be rusted to the dizzy shaft.
All are serviceable. Board member Nightrain posted a link recently to a source for new springs should you find yours are broken.

EDIT: by the way, the electronic dizzys probably don't have four-lobe cams on the dizzy shaft. Therefore, in the text above, when I refer to four-lobe cams, that is reference to the pivoting part the dizzy rotor snaps onto.

[frog998]

Cheers, will have a look tomorrow.
Will proof mark the dizzy to the engine before removal just in case everything turns out to be OK, hopefully will find something though.

[frog998]

Quick update.
Dizzy is a Lucas AUU Electronic type.

Stripped down the dizzy all seemed OK but cleaned everything up i could see, all weights are free, cleaned and sprayed the vac canister as this seemed a little stiff.
Rebuilt everything, fitted it back to the car and now seems to be advancing when rev'ing the engine.
Have set timing to 5deg for the time being but will adjust after i have given it a good run out.

[dklawson]

That's very encouraging news.

As a footnote to the work you've already done, that center screw that held the rotor mount to the dizzy shaft should receive a drop of oil. I mentioned it might be covered by a felt plug. In the older distributors that felt plug was there to hold oil and slowly release it to lube the pivoting spindle parts. Even if the felt plug is not there, remember to put a drop of oil on the screws to keep things loose.