32 replies to this topic

[red81]

Interesting to see that you noticed your clamp was allowing the dizzy to turn.  I've just had a major failure with my  45D4 on my Midget but they are used on minis too, due to the ring clamp allowing the dizzy to creep & turn, the engine stopped in the middle of nowhere and the dizzys a right off.  The MG forums seam to think this is common, with this type of clamp.  So it may be worth putting a paint marker on your dizzy so you can check every now an then, to see whether its moved, a possible contributing cause to the poor running issue in this topic.

Fortunately I still have my old original Lucas dizzy which is far better than the cheap new one that got wreaked, does any one know of any firms that can recondition them? cause i think it may be better to recondition than to buy another cheap Chinese one.

[sonscar]

It is possible because over tightening the clamp crushes the dissy body.Steve..

[panky]

Interesting to see that you noticed your clamp was allowing the dizzy to turn.  I've just had a major failure with my  45D4 on my Midget but they are used on minis too, due to the ring clamp allowing the dizzy to creep & turn, the engine stopped in the middle of nowhere and the dizzys a right off.  The MG forums seam to think this is common, with this type of clamp.  So it may be worth putting a paint marker on your dizzy so you can check every now an then, to see whether its moved, a possible contributing cause to the poor running issue in this topic.

Fortunately I still have my old original Lucas dizzy which is far better than the cheap new one that got wreaked, does any one know of any firms that can recondition them? cause i think it may be better to recondition than to buy another cheap Chinese one.

 

Try the Distributor Doctor

 

http://www.distributordoctor.com/

[Edington]

Latest update. Well the head's off and harden valve seats look OK so can strike that off the list of possible causes, in fact it all look in good order. Will be double checking the timing with a clock gauge which should be more accurate. Ordered a new copper head gasket from minispares never reuse it's no worth it!

Attached Files

•  220715_head off.jpg   57.36K   5 downloads
•  220715_timing set up.jpg   73.04K   4 downloads

[sonscar]

Bit of a dark spot on the block between one and two?head gasket leak?hard to tell from a photo.Copper gasket would not be my choice(is there a choice?)as they are less surface tolerant in my limited experience.Steve..

[cal844]

On an A series Always use a composite gasket, I've seen just how bad a copper one can be on a totally true engine and head...

[viz139]

You say you fitted an unleaded head rather than converted to unleaded. Did you specify a cc in the head or state that you are running flat top pistons. I had a Cooper come into me once with a CR of 15:1 on a stage 3 head, swapped for  a standard cooper head and it ran perfect.

[Edington]

The head was already converted when I acquired it some years ago. Its cast number is 12G295 and the flat topped pistons are +30 thou. When I originally fitted the engine the CR on all chambers was 10:1. Having stripped the head it appeared to be ok if not a little black but it's not been reliable enough to give it a good run yet! photos show the head before initially fitted along with a close up of a hardened seat. I decided to lap all the valves even though they looked ok and fitted better valve stem oil seals rather than the small 'o' rings. Will refit when the new head gasket arrives.

Attached Files

•  131003_3.jpg   38.16K   2 downloads
•  131003_4.jpg   36.16K   1 downloads

[Edington]

Further update and it's beginning to drive me to despair! All fitted back together. I now have confidence in the timing marks having remarked them while the head was off. I also decided to replace the dizzy with a new equivalent from Powerspark and I also double checked the twin HS2. 

 

So here's the issue. With the timing marks and dizzy roughly lined up to number 1 cylinder it didn't fire from cold (with choke) but after slowly advancing the dizzy it picks up then revs straight up to + 4,000rpm which suggests quite a few degrees of advance. After switching off I reversed the dizzy bit by bit (reducing the degrees of advance) and it started only to rev up high again. So having completed this process a number of times until the engine wouldn't start, at no point could I get it to tick over smoothly. I then decided to disconnect the vacuum tube from the dizzy and was surprised that the engine ticked over at just over 500rpm and using a strobe noticed that the timing marks were similar to what I originally set when I first started this exercise. I let the engine run up to normal temperature and pushed the choke in at which point it died. This suggests a weak mixture. The following day when things had cooled down I made the mixture richer but still had the same starting problem. I eventually managed to get it going by further adjusting the mixture but again it revved to over 3,000rpm along with a gurgling noise from the exhaust and the exhaust manifold glowing red! Timing checked and appeared ok. Any suggestions as I'm getting thoroughly disheartened! 

[sonscar]

To me a glowing manifold is most likely retarded timing.In my experience advancing the timing on an engine may gain 500 rpm or so,not four thousand.I would look towards air leaks.Steve..

[Edington]

Thanks Steve. I will continue to plug away at it hopefully one day I'll see the light!!

[bpirie1000]

Following topic.
Local guy to me has same issues.
Completely agree with air leaks. But finding them is the issue.....
Any pics of your carbs.?

Do they have any travel in the throttle/choke spindles?

Needles all centered?

Wefound that the jet seamed to stick in the central bearing seat and left throttle open (causing the high revs)
But still not got to the bottom of it yet.

Now thinking at looking at needles and springs....

Minefeild of things on these pesky twin carbs....

[Earwax]

On the pursuit of air leaks

 

For manifold studs -do you have stepped washers and or are you sure the inlet and exhaust flanges are the same thickness - Might be making things up here - but in the photo where you can see the exhaust header, the internal wall of the cylinder 4 pipe seems a differing colour to the outer side-  maybe less clamping pressure - maybe nothing

[Clip]

I’d still be checking for air leaks. Have a look at the thickness of inlet and exhaust manifolds - the opposite of this:

 

https://www.theminif...ith-washerbolt/

[andyapanel]

Could you have put the distributor in 180 degrees out?
Good luck, it sounds like an annoying problem