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MG MGB Technical - Start up, cam bedding and carbs.

A thought ive had and been pondering is this;

How can I best set up the carbs after an engine rebuild and before starting and bedding the cam in? The carbs are NOS refurbished and unused HS6.

A small doubt, well a huge fear of mine infact if Im honest, is the thought of the carbs being so wrongly set up that everything dies mid cam bedding-in and perhaps not starting again.

No biggie youd think but Id rather bed the cam in comfortably withought any stop starts if possible and be reasonably confident of a smooth start.

Im a few months off a final finished engine and rather get some sleep instead of lying there thinking of stuff like this!

Thoughts tech tips and advice greatly appreciated!

Jamie
JS Ahlund

Jamie,

Loosen the clamp that joins the two throttle shafts. Back the throttle stop screws all the way out. Rattle the shafts (opening and closing the butterflies) to get the butterflies seated in the closed position. After seated, hold the butterfly closed and turn the throttle stop screw in till it just touches and is about to open the butterfly. Do the same with the other carb. Hold both of them closed, and retighten the clamp between the shafts. Turn both throttle stop screws in about 1 turn each. Be sure to do both the same. That pretty well synchronizes the carbs for airflow.

Then, to set the mixture, turn the jet adjusting nut up (leaning the mixture) till the top of the jet is flush with the tube it rides in. This is best viewed from the top with the piston and dash pot removed. Do the same for both carbs. After they are flush, back the nut off by about 12 flats (two full turns).

Check that your choke is operating, and that it returns home when released. Make sure you have the oil in the dash pots.

At this point, the carbs should be near enough to run long enough to bed in the cam.

Charley
C R Huff

Not sure but I don't think the odd stop/start is a problem when bedding in the cam, it's low speed idle. But Mr Burgess will tell you.
Allan Reeling

Thanks for the very helpfull replies!

Charley, exactly what I was hoping for, a clear easy to understand breakdown of how to do it. Much appreciated and copy pasted to my journal. Thanks!

Allan, I think your right. Stopping shouldnt be a problem, its the non re-starting or even a lapse in smoothness that causes stops I was mainly worried about.

My first MG engine build and Ive spent a small fortune my wife knows absolutely nothing about. All bases covered is the plan, minimise surprises and not jeopardise my investment. With some carefully planned luck I wont start swearing at the top of my voice in the garage and so hopefully she will never find out.
JS Ahlund

Jamie,

The other thing I would add is to do your initial start up with two people. If you are in the seat keeping the revs up to bed the cam, you don't know if oil is spraying out of a loose filter, etc., or if coolant is dumping out of a loose hose. So, you need a spotter on the engine.

Charley
C R Huff

As Charley, but, back the jet adjust nuts off only 10 flats, and screw the idle screws in 1 1/2 turns. You will need the choke to start, but then push it back in. The 1 1/2 turns should give you around 2000 rpm, and the 10 flats will be right for a warm engine - and you don't need to sit in the car, so you can watch yourself.

FRM
FR Millmore

Thats another great tip FRM.Thankyou for sharing- also copy pasted to my journal.

Its stuff like this that is seldom found in manuals.

I do have a good friend in mind that will really appreciate being part of the last leg of all this. As well as an extra wrench, I will need another head and two extra eyes just to witness it all and share the moment.

JS Ahlund

This thread was discussed between 22/01/2013 and 07/02/2013

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