Lister D starts perfectly, runs relatively smooth.. then rough, then smooth again when warm

I hope someone has got some ideas on this one....

I can start my Lister D perfectly first time.... in fact even after standing for long periods... it then runs okay and relatively smooth, but after a short while as it starts to warm up it becomes very uneven and shakes around badly, but then when properly warmed up (ie. not boiling, but say hotter than 60 deg C for example) it is perfectly smooth.

its running on 1000 rpm governor springs at the moment, and when it gets properly warm it is fine...

there is a period of say 15 minutes as it warms up it jumps around a lot in this in between phase of when starting to warm up, but not properly warm. any ideas? is it anything to do with the timing?

Given it starts amazingly well from cold then I am ruling out compression problems, and similarly spark problems.

Any ideas?

wonder if you have plug fouling - cleared by heating enough to burn off contamination? Not sure how that would fit with good cold running though........

yes, and I might add that during this mid "warming up period" the rough running gradually increases, to get really bad, like nearly jumping around off the ground.. then after a few minutes subsides. it's sort of like a little mountain peak of bad running that builds up then subsides fairly quickly...the only thing I can think it is maybe to do with the crappy modern petrol?

Maybe carburettor/fuel settings. Also, is the governor working smoothly when cold, before starting, all linkages well oiled and free to move ? I take it when you start the engine it immediately runs up to the same speed it is running at 15 minutes later when you say it is running well ? I would be tempted to give it more fuel at first by opening up the needle and then back it off when the engine gets warm. Cheers Dave

fowlerfan wrote:Maybe carburettor/fuel settings.  Also, is the governor working smoothly when cold, before starting, all linkages well oiled and free to move ?  I take it when you start the engine it immediately runs up to the same speed it is running at 15 minutes later when you say it is running well ?  I would be tempted to give it more fuel at first by opening up the needle and then back it off when the engine gets warm.  Cheers Dave

Thanks for that, they are all oiled and I have tried twiddling around the mixture. similarly the governor housing is all cleaned out inside etc.

it appears that the speed is the same. (ie visually). though without sticking a handheld tacho I could not be totally sure, maybe a good start therefore would be to get a handheld tacho to actually check this. (I have found a simple small engine one for less than £10 that's powered by its own lithium battery) http://www.amazon.co.uk/Tachometer-Stroke-Engine-Outboard-Mercury/dp/B00ACDP6YU