504 - hesitation off idle

Pug_405_Mi16

Pug_405_Mi16

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Fellow Frogger
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Hello All,

I put my 504 away before winter as it was running poorly and I really ran out of time to work on it.

I've dragged it out and today have replaced the points, condensor & plugs. I have also put a kit through the cabie and cleaned it up thoroughly and while it is running much better it's still not perfect.

When taking off (even when warm) it has either a bit of a hesitation or a slight backfire unless you give it a few revs. I'm not really sure where to go with it as I've gone through pretty much everything I can think of.

Any thoughts?

Ben
 
hi ben,first I would check vacuum advance capsule in distributor,this can be done with dist cap rotor button and dust cover off,vacuum hose on capsule and suck on hose to see if advance capsule shaft draws in and moves ignition points to advance.second would be carby accelerator pump discharge nozzle in primary throat to see if fuel is being discharged into carby throat when throttle opened.third check electrical...spark plug gaps...6mm?.spark plug condition and insulators,spark plug leads,low tesion(points) wire coil to distributor,condensor condition.initial ignition timing advance setting,ignition point gap?air filter is not restricted?.any vacuum leaks from inletmanifold/carby base........just a few ideas jim.
 
G'day,

look at the earthing of the action plate within the dizzy.

Remember the ancient dizzys, they had this bit of very flexible wire running from the plate to the body. In more modern times someone decided that they could save twenty cents a unit by replacing it with grotty spring things bearing on the greasy plate... :rolleyes:

So, every time you touch the pedal you alter the manifold vacuum and the plate wanders around over all these intermittent connections... :evil:

cheers,
Bob
 
All good ideas. My money is on the vacuum advance being stuffed.

I have a 505 electronic dizzy, coil and module for sale if you'd like to convert over. It was the best thing I ever did to my 504. Bloody points....you get a good run of luck, then a bad run....

This dosn't really fit your symptoms, but don't forget that the spark plug insulators are often overlooked as a source of misfiring.
 
Thanks all for the replies,

I've confirmed the vac advance is OK, and I am pretty confident there are no other air leaks. I have pulled the carbie down and replaced all the gaskets including the base onto the manifold. I ensured the manifold was tight on the head while the carbie was off.

New points, set correctly with dwell angle, new condensor. New plugs and I have visually inspected the plug insulating tubes and they don't appear to have any cracks.

Thanks for the offer Beano, I've got a couple of those setups here already, but this car is very original so want to keep the points dissy.

Could it be the mixture is a bit lean? It goes fine once it's off idle and up and going?

Cheers and thanks again

Ben
 
Accelerator pump adjustment? Throttle spindle wear?
 
All good suggestions.

If you have a timing light you might check that the to see if the advance is smooth, and that it is timed correctly.

Do you have the same symptoms with the air filter disconnected?

Have you tried peering under the hood in the dark of night to see if there are any extraneous flashes?

When was the last time the tappets were set? A head re-tension while you're at it.

P
 
Thanks for the replies,

The issue is solved, I looked in the logbook and the last time I put fuel in it was December 2015!! It was nearly empty so a fill up with a fresh tank of 98 and its away!

Cheers
 
All good then.

I've never been able to tell tell from a visual inspection if the spark plug insulators are ok.
 
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