POPPING UNEVEN IDLE

[horrie58]

My grey motor is bog stock and has developed  an uneven idle and run to 2500rpm.At idle the motor is fairly smooth as it should be however intermitantly it gives a little shake,like a hiccup every now and then,whether hot or cold.at the exhaust i can hear what sounds like a popping noise.It runs like this up to 2500rpm,on the road under load there is no roughness or power loss.Valve clearances ok.timming ok,

[FCwagon]

Hi Horrie,
Sounds electrical to me. You'll need to check that plugs & points are good. Check the dissy cap has no cracks. you can sometimes see a light carbon trace where it's cracked. Pull all plug leads out & check the connections & cap there too. Check the coil tower for cracks or burns.
An old trick looking for electrical shorts is to fold back all the rubber boots on the HT leads and check for sparks jumping when it's dark.
cheers,
Leigh

[brads59]

Valve maybe? :-/

[craiga]

Horrie,

You said you checked the timing, but did you inspect the points and gap them correctly? Burnt points are a sign of a faulty condensor which will give you problems like you describe. The condensor is usually the last thing people go for - but 40 year old capacitors tend to be a bit long in the tooth

If you have access to a tune up machine it should be pretty straightforward to identify the culprit. Leighs right about carbon tracking too - its always good to remove, inspect carefully and clean all the engines high tension components as a starting point - I've seen rotors that are cracked and allowing the HT to short to the centre shaft of the dizzy, or dirty plug insulators that have allowed carbon tracking to earth. Remember you've got 30,000 volts pretty keen on finding the easiest way to ground - either by the correct method via the plug, or any other way it sees fit!!!!

Have fun.

Cheers,

Craig.

[Graeme McKie]

Mums grey was doing the same thing. Suspected crook spark plug. Got hold of one brand new plug. Pulled number one and fitted the new plug. Still the same. Pulled out the new plug and refitted the original. Carried out the process until I found the culprit.  Number six. Always the way. Now idles beautifully.