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MG TD TF 1500 - Adjusting the jets

Simple carburetor question: the jet nuts tighten clockwise. From closed, you open them out. Does this increase or decrease the mixture? Is it at max or minimum when the nuts are fully tightened?
Geoffrey M Baker

Your tapered needles will sit farther up into the jet as you tighten the nuts. Withdrawing the needle.. (Loosening the nut) Enriches the mixture. Regards, tom
tm peterson

It only makes a significant difference at idle. To change the mixture over the rest of the rev range you need to change the needle. Easy to do, but difficult to get right.
Dave H
Dave Hill

Changing the idle defines the mixture across the entire range as programmed into the needles.

Floats set at 7/16, and jets set below the bridge .065 will result in a good starting point.

Dave Braun

Geoff, after reviewing your comments on recent posts, it seems to me your "Chasing your tail". Too many changes being made and not solving the basic problem your experiencing.

If your carbs are even close to being in operational condition, set the adjusting nuts on your jets to 6 flats down on each carb and leave them alone until you find out what is wrong with your engine running roughly.

Recommend you go back and check the clearance on your rocker arms to confirm none are too tight. Then do a careful compression test (Wet and Dry). With your rebuilt engine, they should be within a few pounds of each other. If not, something is seriously wrong and must be corrected. Yes, the rings will seat better after breaking in, but that won't account for a big difference in pressure between cylinders.
After completing a successful compression test, install a new set of properly gapped spark plugs. (what plugs are you using?) Use an inductive timing light on each spark plug wire ,one at a time to confirm each is firing evenly. With the engine running at a fast idle, each plug wire should show a steady even spaced strobe flash. If not, something is wrong, and you must find out what is wrong with your wiring/ distributer circuit. Finally with your engine running smoothly, and the previous checks completed successfully, you can begin to worry about correct mixture.
Richard Cameron

The Chicagoland MG Club T Series How to do a Complete Engine Tune Up Parts 1 & 2 by Skip Burns details a methodical step by step approach. I plan to follow this closely when I finally get around to starting her up. It's available on the Internet. Cheers
Peter TD 5801
P Hehir

Richard, I'll be doing those things. Flats are now set at 6. While the engine is running more smoothly now, I still think I've got some weak sparking on a couple of cylinders so I will test this as you suggest.
I have a new distributor rotor, cap, wires, coil, condenser and fairly new plugs.
I want to reset the plug gaps. I'll have to look up and see what they should be set at...
Geoffrey M Baker

Geoff, what brand/# spark plugs are you using?
Richard Cameron

Has your distributor been overhauled new bushings, advance springs, functioning advance weights etc?does you
Distributor have a ground strap?
W. A. Chasser Jr

Distributor has a ground strap. I stripped and cleaned the distributor but did not overhaul springs, weights etc. I'll have to check the plugs, Richard.
Geoffrey M Baker

Plugs are NGK BR6HS
gapped at 035
Geoffrey M Baker

As I read it, according to the WSM, the spark plug gap should be 0.020 to 0.022.

Jim B.
JA Benjamin

Geoff, Since your still using points, the engine might be a little happier with the plugs in the .025" range.

Have you had a chance to use an inductive timing light to view the strobe and see if you actually have a misfiring on any of the cylinders? You don't have to point it at a timing mark---Just observe the strobe flash, looking for consistent firing.
Richard Cameron

They're 022 now.
Geoffrey M Baker

One thing that I didn't see mentioned in this thread, is, when you do make any adjustment to the nuts, make sure that you manually push up on the assembly to make sure that it is seated properly in the carb body.

Steve Wincze

This thread was discussed between 21/01/2016 and 25/01/2016

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