Running rough until warm

antodeco

Hi all,
My mini, when started, runs horrendously rough. If I don't pull out the choke nearly all the way the engine drops and dies. If the choke is out, and I push the accelerator, the revs "limit" at around 3k, sounds like it's hit a rev limiter and then dies.

If I'm driving, I can use the choke as an accelerator instead of the pedal, as otherwise the same thing as above happens. After about 20 minutes, it slowly begins to run ok.

What could be causing this? Im thinking it's that the fuel timing is out, hence the choke giving it a higher flow?

Thanks

sogood

The fist and simplest thing I'd do is check that the choke cable itself is doing its' job. Check that it's firmly attached/clamped at the carb and not slipping, thus giving you only partial choke and so, adding to rough idle. Otherwise maybe the carb itself needs an overhaul?

antodeco

Choke is all good. Even with the accelerator pushed its still limiting the revs, peaks and then dies. It may be the carb. I cleaned the dashpot and refilled with oil and that made a partial difference but then went back to normal.

hi5

Check the fast idle cam, the little snail like thing the idle screw lands on, it could be jamming?

corktina

Is the timing OK?

swarlb

Check your plugs and see if all 4 are sparking.

ianobrien

OP, you do know that the choke is shutting down the air flow into the carb? That's contributing to the rev limit. Also, revving a cold engine above 3k isn't the best idea.

I don't know enough about SU's to comment with authority but I assume once warm its running OK. It's hardly a damp dizzy and sorting itself when heat from the engine dries it out. The dizzy is in the most intelligent place right inside the grill.

As an aside, I once had it that a car wouldn't rev above 3k, warm or cold. The problem was stuck weights in the dizzy.

Edit. It isn't an air leak after the choke but before the venturi? I take it the standard air box is still attached.

okistag

antodeco wrote: »

Hi all,
My mini, when started, runs horrendously rough. If I don't pull out the choke nearly all the way the engine drops and dies. If the choke is out, and I push the accelerator, the revs "limit" at around 3k, sounds like it's hit a rev limiter and then dies.

If I'm driving, I can use the choke as an accelerator instead of the pedal, as otherwise the same thing as above happens. After about 20 minutes, it slowly begins to run ok.

What could be causing this? Im thinking it's that the fuel timing is out, hence the choke giving it a higher flow?

Thanks

Hi Antodeco

Try Alan Egan at (Classic Vehicle Company) 086 873 7774
He is based in Terenure and is a SU specialist and also stocks many parts.
Well worth a call.

Henry Ford III

Ignition and fuel sytems all need to be thoroughly checked.

Coil, plugs, points, ht leads, dizzy cap and rotor arm.

Fuel filter, air cleaner, and carb jets and settings.

Agricola

Yeah have similar issue which has improved but hasnt completely been resolved. Starts perfectly every time when cold but if engine has cooled, it seems to splutter alot, as if firing on 3 cylinders. Changing fuel pump, fuel filter, changing plugs and doing the timing has lessened it a lot but still get it the odd time.

type85

Few things you can try yourself,(ref image)

1, Pull the "choke" cable out/in and look/check that the main jet/ choke mechanism is moving down and then returning back up.

2, Remove the dashpot piston/damper and make sure the bore is full of oil, this can be done by feeling for resistance as you push/pull the damper in and out. If low/empty top up with some light oil (engine oil will do).

antodeco

Thanks for all the replies. Going to change the sparks, leads, air intake and have another look at the dashpot. I originally had a burst radiator hose (going into engine). Could that airlocked anything?