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MG Midget and Sprite Technical - Engine stutter when turning right!!

Odd one here.
Not expecting anyone here to have my setup but any suggestion welcome.
1100 with Shorrock supercharger. Single H4 carb. All runs fine except when I turn sharply right when I get an immediate stutter which clears when I press the accelerator. Doesn't do it when I turn left. Doesn't do it when I richen the mixture by a couple of flats.
Doesn't do it when car is stationary and wheel is turned (straw-clutching)
All electrical connections seem good. No fuel leaks, float height all checked out and good. Carb piston falling freely, dashpot filled correctly, choke and throttle all free correctly returning.
Odd and a bit annoying.

Simon

Simon Wood

Simon, when this next happens watch the rev counter. If the needle flickers and jumps violently it could indicate an electrical rather than a fuel problem.

Something like an unsupported plug cable or a wire that swings out as you corner and shorts against the bodywork perhaps?
GuyW

Many moons ago I had a similar problem when turning left. Eventually the fault progressed to also climbing steep hills.
The fault was an internal short circuit within the coil created by the varying level of the oil therein.
Alan Anstead

I second Guy's suggestion. A SAAB that I had stuttered when making left turns. It turned out to be a not vey well secured lead to the simple electronic ignition module that I had fitted making contact with the block.
C Mee

That the problem goes when richened a couple of flats indicates a fueling issue, and effects of fuel surge in carbs when cornering hard are not unknown.
Is the carb is mounted with the intake facing firward or backwards, and the bowl towards the left (viewed from the drivers seat) that could be what is happening.
Altering the float level can help, but can also make a rich stutter in the other direction.
Best solution would be a carb in which the bowl is cantred aroung the jet, such as HIF
Paul Walbran

Misread that! I thought when Simon said "doesn't do it when I richen.." meant it didn't clear when richened. I think Paul is right, it is unlikely then to be an electrical problem.
GuyW

Carb to rear. Float bowl to left when viewed from drivers seat. Frogeye so mechanical tacho.

I like Alan's suggestion. Will swap the coil and see what happens.
Thanks chaps
Simon Wood

Would add that this is a recent problem, so I feel that something has "changed". Imagined that it must be electrical but now not so sure.
Will report back
Simon Wood

Check also the LT wire between coil and dizzy.I have had one break internally, leaving the insulation intact. When the engine bay heated up the insulation warmed and moved under heavy braking which caused it to stretch and disconnect the wire strands inside. Just to make it hard to diagnose, when it cooled the insulation shrank again, pulling the wires back into contact.
GuyW

Checked the float level once again and set it a little higher. Also removed some crud from the needle valve and the stutter seems to have disappeared.

Still not sure that I understand why turning right was the only trigger event.
Simon Wood

With the carb in that position and bowl on the left, cornering forces will lower the fuel level in the jet when turning right. If the level in the bowl is a little low already that could be enough to make a lean misfire.
I had the opposite problem with the Weber on my B at one stage with LH handbrake turns causing fuel to surge through the pump jets and give a rich misfire. Solved by lowering the float level.
Paul Walbran

Paul,
any chance please you could put your method for sorting the tyre pressures as last time I think there might have been words missing - or I'm even more dim than usual (surely not!).

The 10% front to rear, and so on.
Nigel Atkins

I had this stuttering a few years ago on right turns. It was a loose distributor cap clip.

Flip
Flip Brühl

Nigel, is your "words missing" a comment on my fat fingers needing to iterate to greater accuracy when using my phone (if so then well deserved and enjoyed), or are you actually going off topic?
Paul Walbran

Hi Paul, thanks for replying.

Yes I was going O/T as I saw you post and wanted to catch your attention please.

Standing in a tower of glass I'm not throwing stones with my chubby digits.

I saved a post of your about getting the correct tyre pressures for when I changed tyres (and size), now I've changed tyres and on reading what I've saved I think there are words missing. See the following. -

"Set rear 10% higher pressure difference than front (rear higher by 10%).

See what the car feels like on your favourite test road, then swap pressures front to rear and try again (front higher by 10%).

The combination that feels least stable has better grip at the front, so that pressure is better.

If the better pressure was higher, - [which higher please, front?] - then raise the back pressures 20% (so now 10% higher than the "good" front pressures) and try again.

If the better pressure was lower, then lower the rears 20% and try again.

Repeat this process until you reach a point where there is not much difference when the pressures are swapped.

If you can't make much sense of it at 10% difference you could try more, but be aware the car could get very unstable and lose it..."

I went out today to give it a try but too many cyclists and then we had light rain. I decided to have my starting pressures as 24f, 26r as 22f, 24r I was running felt too soft but already 24f, 26r feel a bit hard. The tyres were my third or fourth choice for availability and time constraints, they feel like saloon tyres.
Nigel Atkins

Aha.
A few wines past the yardarm at present, will be more coherent tomorrow!
Paul Walbran

Drinking and operating a forum! :yikes:

Thanks.
Nigel Atkins

Nigel, I think this takes the Golden Biscuit for thread drift!
Suggest you make a list of all the combinations of pressures, front and rear, go out and try them all, if you hit the hedge with any, cross them off and try again! Once you get to the point where you’ve managed to miss hedges, cows, cyclists, etc, that’s job done!
Simon :)
S Holt

Nigel, when you have finally got the pressures at their Goldilocks settings ("just right") remember they will need adjustment when you get to the end of your residential road. And then again when you get to the dual carriageway. And again before the roundabout. And again before joining the motorway. And the A5 to North Wales uses a different surface dressing, so . . .

;-)
GuyW

Or, you could try adjusting your driving style according to the road conditions. I believe this to be possibly without even getting out of the car!
GuyW

Simon,
you'd put you'd sorted your issue so I thought I'd get Paul's attention whilst I could as he's not a frequent visitor here but does offer lots of help and advice when visiting.
Nigel Atkins

Guy,
I'm after a general compromise setting that I can then adjust my driving from with attention to circumstances.

The pressures seemed about right for the roads in Cumbria but perhaps I should have called by your place for your greater experience and longer time of driving. I would also take the biscuit, or two, or chunk of cake.
Nigel Atkins

OK, clear head. I hope.
In answer to Nigels question, the "better" pressure is that of the front tyres when the car feels twitchier (when comparing the change in feel after swapping from rear 2psi higher than the front to rear 2psi lower than the front).

At 2psi the differences are usually smaller and harder to notice, if so try 4psi but take care.
Paul Walbran

Thanks Paul.

I can do 10% as I've learnt to use a calculator, electronic, not a slide-rule.

I must remember to allow for the various journey specific spares I need to carry to, I'll cornerweight without and with navigator. Then I'll get on to the four adjustable dampers, and wrapping the rear springs, and . . .
Nigel Atkins

This thread was discussed between 01/08/2021 and 13/08/2021

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