Hey folks,

A while back I was having issues with cylinder 2 not firing. I checked everything electrical and determined everything to be OK. Plugs, leads, dizzy, etc.

The old manifold gasket had a bit of a bend in it, so I figured now was the best time to replace the single HS4 carby with my newly (slightly) refurbished twin hs2's.

After replacing the carbies, manifold, and manifold gasket, and finally starting it up (after a month), cylinder 4 is now misfiring! Aaaagh!

I've again played switcheroo with leads and plugs and the problem remains in cylinder 4.

I've sprayed carby cleaner around everything and can't identify anywhere which might be contributing to vacuum leakage.

I'm just wondering if anyone has experienced something similar and knows what might be causing this?

I should mention I haven't quite got the mixtures/idle speed ideal yet (one is running rich, the other pretty lean).

Thoughts? Any help greatly appreciated as I'm starting to pull my hair out!

Pat.

Ps. went to the QLD mini muster (my first time) over the weekend. Was great to see so many good looking cars. Has definitely given me something to aspire to for the next show.

Just bumping this up, haven't had any luck with my issue...

I'd be checking basics. Spark , fuel , compression. Then move on. It can't be fuel, not with number 3 firing (shared), you can discount spark by trying known good plug and looking at spark. Compression is an easy check, you need at east 70psi to run.
If all these are OK, then you have things like as you mentioned Such as manifold leaks. You should be able to run engine and check the spark at that lead, make sure its good and 'thick'. Things like bent dissy shafts, worn breaker cams, slightly dud condensors, cracks in cap, all contribute to poor spark. If you have screw in compression gauge with a valve in it, take the valve out and screw the gauge in engine and run it. If it's got a sticky inlet or exhaust valve it'll show up as a 'miss' in the gauge pulses. You mention that you have twin carbs? Which is rich / lean? If the 'missing' cylinder is too lean it won't fire properly, too rich and it might be fueling up the plug.
Sorry if this sounds like the ramblings of a mad man, I'm just writing things as I think of them. It's so easy to do things like diagnosis if the cars sitting in front of you, bit harder via phone/ internet

1,3,4,2, check and then check again... i probably need to tatoo this to inside of my forearm.

Its printed on the original manifolds from memory as part of the casting. Must have been a sanity check for many a home mechanic....

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks Peter,

All still seems to be the same. It's been a while so I can't quite remember which carby was running rich/lean, so I'll double check fuel mixtures.

I'll double check the spark at the lead to make sure! Otherwise I'll move on to checking the condition of the dizzy.

Will keep you all posted. Thanks again for your help.

Check the resistance of your plug leads and the coil lead. A friend's 998 Mini was doing this, but fouling 2 plugs not 1. All the plug leads were over 20K resistance, they would not read on the 20K ohm setting of my meter.
So, I binned them and fitted a new set of Russell Engineering's inductive core leads (500 ohm), cleaned all the plugs' electrodes with the oxy, and Vroom!
Going like a rocket... and has been for 3 weeks.

Cheapo leads like the old Top Guns have a core of carbonized string. They go bad with age... eventually going open circuit. The inductive core oness do not.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Cheers Doc,

At the moment I've got a set of Bosch SuperSports inductive cores on. I checked the resistance of all five 6 months ago when cylinder 2 was misfiring, but I'll double check again.

You could try swapping the coil. I had a recent miss and it was dropping a plug and it was the coil in the end.

Try and get a new one. I did swap it out for a second hand one and had the same problem. So I swaped it back.

It wasnt till I blew the circuit breaker in the garage and it was pitch black that I could see blue sparks tracking around the coil.

As said try a coil first.
Also check the points condition & gap, and the condenser. There was a bad lot of Bosch condensers about recently. If you have one of these in, try another brand, or even a s/h old one.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

well my moke is now missing as well.

I have a no name brand condensor in it so brought a new one today and will see if its the issue

I have replaced all of the electrical parts so only thing left is the fuel pump.

Have you tried the new condenser Kiwi? How did you go?

Got to it today. Condenser was loose so most likely the issue so I thought swapped it out anyway. Reset the point etc.

Checked the advance mechanism and it was full of fuel.

So found a working unit in my box of bits. My last one.

Starts on the first click and runs like it should.

The condenser was a known brand. If that helps

Time to bin the poor asian made points and condenser and fit an electronic module? Or a Pulsar dizzy...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Agree. Santas bringing the moke one for Christmas. Dont tell him lol