Newbie, I know, the car deserved better.

[Mahesh]

Took the car for a spin this morning, much better than yesterday, smoother but not quite there yet.

Feels like a very obese cheetah, wants to run but, nah.

Have to check the oil level, I think its a bit on the high side and change the breather hoses and spark
plug tubes, followed by a change from the contact and condensor to the magnetronic I got from Ebay.

Having said all that, the idle is much improved,

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[TahitiSPRINT]

Are the compensation holes for the SU suction chambers 'open' and not blocked by the backplate of the new filters or the gasket?

I had this kind of problem once on an SU'd Mini with strange idle behavior and high fuel consumption...

[Mahesh]

Thanks Ronald, I've been checking without the air filters and back plates, but there is an inconsistency which I don't seem to be able to nail down.

Yesterday all smooth but when I removed any one of the breather pipes the car would stall.
This morning re-set mixture to base settings and idle screws and re-done setup, now car will
not stall even if both breather tubes are removed.

Have ordered new breather pipes, may just cling film them tonight for another test.

Oddly enough, colortune shows blue through a wide range of mixture settings today.

Also the piston lift on the rear carb makes a difference, absolutely none on the front carb, even if I lift the entire
pin to the top (damper fluid comes out).

Varying results make difficult an easy job, but determination will find the problem (soon).

If all fails in the next couple of days, I may even test with my spare set of carbs.

[Jon Tilson]

Bring it over here....

Jonners

[James467]

Tell me if you do, I'll come up and say hello. Mahesh can make the tea!

[GTS290N]

Bring it over here....

Jonners

It could save you a world of pain and gain you tips that could be years in the learning on your own......

[Mahesh]

Many thanks for the offer Jonners, and as GTS290N said it would be a very good idea, but
there is an inconsistency which I have to nail down first, for example,

today,

Warmed up the car, had to hold the pedal as I have not put the fast idle screws back into position, not a problem,
however the piston lift pin on the front carb made a difference as opposed to yesterday, no adjustments made yet.

Idle when warm changed from yesterday, so readjusted the mixture and now both piston lifts increase rpm but no
decrease when held, I can't adjust any leaner without engine stall.

Listening to the exhaust note, made some more adjustments, and took the car for a spin, which was a lot better
as now, moving away in first is not so hit and miss and does not need excessive accelerator pressing. If anything
its better than in a long time.

Had a cup of tea, (Sorry James you missed this round) and again started the engine to another inconsistency yet again,
rpm had dropped a bit, and idle seemed a bit rough.

What I will do next is, run the car over a couple of days and change the spark plug tubes to the club ones which
will hopefully stop the plugs from fouling, (a few pics of the plugs after will help show the problems) hopefully)
and then change the contacts to the magnetronic as the timing is a bit scatty, reset the timing and then look at
the carbs again. The breather pipes seem ok, as trying to blow through them is nigh on impossible if you block one
end. (petrol does taste good with a dash of oil)

It seems like its a few minor bits here and there affecting the whole, if then no joy, I'll pm you and see what can
be done.

[James467]

If your timing is a bit scatty you might have some play in the dizzy shaft.

But.....

I'd like to see your ignition system set first with the Magnetronic and the timing set, do you have new leads, cap and plugs on?

Then have a look again at the carbs.

Reset them and do the fast idle and I'd say ditch the colourtune. As well as the Wiki this is a nice how to guide: http://www.mgexp.com/article/su-tune.html

If you are still getting the same issues then Jonners, do you recon the Waxstat jets are causing issues?

[Jon Tilson]

Possibly but I'd be more for suspecting odd bits of crud blocking jets.

My P6 is doing this atm after standing a while....despite a fuel filter.

Fuel filter just south of the pump is mandatory.

Why use the lifting pin? Do it with a screwdriver. If one carb is sucking more (balance is critical) chances are the faster one will
be off the pin lift anyway.

Set the fast idle cam so it gives about 1200 rpm but doesnt move the jet down. Make sure the jets are always returning fully up
after you work the choke. Often the return gets lazy on one jet and leaves it down a tad, which messes up your mixture setting.

Push the jets up into the carb after pushing the choke off and see if there is any movement. You want none...

You also need to see both carbs are lifting the same when you pick up the throttle. You can go a bit cross eyed looking at both air valves at once.

Jonners

[Mahesh]

Thanks guys,

(Jonners) If one carb is sucking more (balance is critical) chances are the faster one will
be off the pin lift anyway.)

Now theres something I didnt take into account, will have another quick look in the morning.
I know, it's just an excuse to then go for a blast around the roads early in the morning.

I will check for foreign matter, even though the fuel filter is present now, there is a good chance
the fuel pump filter is clogged, float chambers and carb throttle bodies are spotless (that's spotless
to my standards, not James's, but close).

Replaced on the carbs (both)

Waxstat jets,
Throttle spindles,
Throttle discs,
Throttle disc screws,
Float seat valve kits,
Floats,
Choke cam springs,
Damper cap washers, (were missing)
Needles, (BDQ)
Needle guide kit and springs,
Interconnection levers (all 4)
Lost motion levers, (both)
Piston springs (yellow (both)

A lot replaced (majority really) but has improved since trip to Stoneleigh) more
tweaking (meddling) needed.

[MIG Wielder]

I was wondering about the effects of cylinder blow-by in the crankcase with the gasses getting down the breather tubes and then into the carbs; and maybe affecting the mixture. I remember my old Sprint had lots of positive pressure from the oil filler cap until I overhauled it and then there was none. I remember reading somewhere that there should be negative pressure at the oil filler cap with an engine in good condition. Is this correct please ?
Thanks ,
Tony.

[Carledo]

I was wondering about the effects of cylinder blow-by in the crankcase with the gasses getting down the breather tubes and then into the carbs; and maybe affecting the mixture. I remember my old Sprint had lots of positive pressure from the oil filler cap until I overhauled it and then there was none. I remember reading somewhere that there should be negative pressure at the oil filler cap with an engine in good condition. Is this correct please ?
Thanks ,
Tony.

There should be neg pressure at the filler cap if the breather is doing its job. Engine vacuum should pull air (with a trace of oil) through the breather pipes and the filter in the rocker cover. If the breather filter is blocked you can get positive pressure at the filler.

If the rings are particularly bad, some excess oil from crankcase pressure may find it's way into the carbs for the engine to burn resulting in extra smoke, plug fouling and possibly a slightly richer mixture than set.

To Mahesh, I notice you are doing all this with the air filters removed. You do realise the mixture settings will be wrong once you refit the filters and you'll have to do them again? And the engine SHOULD stall (or at least stumble badly) from idle if either of the breather hoses is removed from the carb, if it doesn't, the mixtures are too rich.

Steve

[Mahesh]

Made a start this morning, mainly all negative

Warmed up the car to temp, so I know it's working (ish).

Undone the distributor cap, removed the rotor and splash guard, and then realised the
condensor screw and contact set screw were both loose, and would not tighten up as it seems the
threads are worn.

Just to be sure, removed the contact set and condensor, which resulted in the contact set washer dropping
under the base plate, which then took another 30 minutes with a magnet and small screwdriver to retrieve.

Then put the magnetronic plate in, success, however as soon as the magnetronic unit is screwed in,
the plate comes loose but holds on the first couple of threads, just like the contact set.

Well at least it's one of the problems found.

Need new base plate, Rimmers are doing a clearance on them, unless anyone suggests a better quality source.

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And this pic shows how the magnetronic plate comes loose but will not come off until unscrewed.

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[Mad Mart]

Mahesh, I have several dizzys. Let me have the part no. so I get the correct item & I'll post you one.

[Mahesh]

Many thanks, but I cant find the number you need, I took the base plate out, do I have to separate the two halves ?

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20160326_122753.jpg (317.8 KiB) Viewed 1108 times

Also whilst the plate is out, I gave the shaft a waggle, and it moves around 1.5 to 2mm left to right, is this correct ?

Think there has been a problem here in the past, as the two screws holding the base plate seem to have worn heads,
either someone has been over tightening (seems unlikely, these were loose too) or they had problems removing.