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MG Midget and Sprite Technical - help with timing - I'm going mad

All,
Having replaced the clutch and a small one year hiatus refitting the engine and gearbox I have got the engine turning and burning - all be it rich!!. Static was Ok but when I did the dynamic no marks can be seen. Rechecked the dizzy and static mark - 7 degrees and light just on via LT and earth.
Before I go mad - have I cocked up somewhere. As I said I have had it running and am trying to balance the carbs with some hand me down Midlocks - that's another question - what number?

Thanks
D Price

Have you whitened the timing marks with something like tippex? You won't see them otherwise and, other than a Frogeye, they're still difficult to see from underneath the front I believe. I think some people create new marks which are seen from above the pulley.

For carb balancing, you can use a screwdriver, after loosening the throttle linkage, to turn the idle screws. Disconnect the vacuum advance. A length of plastic tube or hose allows you to gauge the airflow into each carb by ear. Having done that, you push the lift pins slightly to see what happens to the revs. It should rise slightly then fall back but not stall. If it stalls, that carb is weak so you unscrew the jet nut by hand about a flat (clockwise looking from top). If revs increases and stays like that (with lift pin pressed again) then that carb is rich so you screw the nut anticlockwise from above. You keep testing between front and rear carb until the correct conditions are met. You might then have to adjust the throttle screws again.

If the throttle shafts are worn where they locate in the carb body, accurate mixture adjustment is difficult or impossible.

Bill Bretherton

Are you sure the plug leads are well separated when you clip the strobe pick up to number one lead. If the pick up is close to number two you can get multiple flashes and this will mess your readings up.


Jan T
J Targosz

Also, using a strobe at idle speed will give a different reading as to doing static timing.
These distributors start advancing quite early.
e.g.
If the static timing is set at 10 -- then with the engine idling at 650-700 the timing will typically be around 14 with a strobe---around 4deg. already advanced

willy
William Revit

Presumably your dizzy is on points and not electronic?
Les Rose

Thanks all. Will try to address points raised
Marks have white paint on.
Unscrew the jet - does clockwise not screw them in?
Throttle shafts are most likely worn but it was Ok before - if I can get them set up it might be time to swap in new bits post summer driving!!

Yep - leads were separate

Will get the car running and see if I can see where they are!!

Thanks again
D Price

D. Price
Yes, clockwise screws them in, but because that's from underneath it becomes anticlockwise looking from the top if you see what I mean.... sorry if I caused confusion!
Bill Bretherton

Bill - with you now!!! cheers Dave
D Price

Dave -'Some' timing lights are directional---If your light has an inductive pickup with a direction arrow, then the arrow points towards the plug for neg earth cars and towards the dist. for pos earth
Also with the quite well insulated plug leads we get now, some older lights won't read through them unless you're right down near the dist. cap with the pickup.
If you still can't get a reading try the pickup on the coil lead instead, you'll get a reading there that will still be ok for timing
willy
William Revit

Will - the light is certainly old - it was my dads and I'm 59!! has all been OK before so not sure what's happening - fresh eyes perhaps!!!
D Price

The first question is what is the timing light? Back in the 1970s the timing light was a "shoot through" light which was connected up to the end of the plug lead and the spark plug. It was very low light output. Later, there was a light that was connected to the battery with an in line connection to the spark plug, i.e. in series, that was much more powerful and produced a significantly stronger strobe effect. Later, there was the indictive strobe light which clamped around the number one spark plug lead and produced a spot of light when the number one spark plug fired. If you are using your fathers's item, what is it?

The most common type of timing light today uses an inductive pick up, which claps around the primary lead, most commonly for the number one cylinder, but not always. (I own a vehicle which uses number eight for timing.)

Thus, it would be good to know how your timing light is activated. How new your spark plug leads are. (Start the car, in darkness, and look to see if you are seening "lightning" flashing off the leads or off the distributor cap. If so, there are othter problems that must be attened to before worrying about the timing.

Insufficient information here to make any form of determination. My friend, Jonh Twist, recommends setting the timing at 32 degrees BTDC at about 3,000 rpm, then checking how well the distributor fits the rest of the curve.

Do not post here on a regular basis, but will check in within the next few days.

Les
Les Bengtson

Les - its the old fashioned plug into the lead and spark plus type. Having set it all up again - I turned the garage light off and hey presto a white smudge about 10mm wide appeared!!

Seems to run OK so that'll do for now 0 just got to balance and make the carbs leaner - lots of black soot at present!!
Dave
D Price

If the engine is equipped with a harmonic balancer, the rubber insert can come loose from the inner portion of the pulley, making the timing notch useless. I found I could no longer time the MGB with the light and when I removed the harmonic balancer, the inner and outer portions of the pulley were no longer one piece. Had this happen on a Volvo 240 as well. Both the B and the Volvo have A/C and there is quite a lot of impact when the compressors engage. Even so, pulley separation could occur on an A Series engine with deterioration of the rubber insert. When I rebuilt the A Series in the midget last year, I replaced the harmonic balancer as a matter of course.

For carb calibration, I suggest removing the dashpots, running the jets up level with the bridge and then turning them 8 flats down/rich. This will provide a base line so that the assembly can be richened or leaned adjusting each nut by the same increment to get the mixture right. Then the air flow can be balanced.

The shop that I use for emission inspections required on the later cars lets me use their machine to bring the mixture on the Midget into spec. (per the label under the bonnet). Final balancing when I get home makes for a perfect carb tune.
Glenn Mallory

This thread was discussed between 17/02/2024 and 27/02/2024

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