Help

Hi there archie and welcome!
A few bits of help here is required as you haven’t said the make, type, model or year of the bike (I presume its a bike..!?)
Have you high mileage? Has it been adjusted?
Ignition coils or sparkplugs is my random guess!

 

Depends on what bike but IACV pipes . Igniter. Plugs. Leads.

 

I remember something like this and it turned out to be the hoses? I may be totally wrong of course but it was the air box sensor hose I think?

 

A common cause of idle fluctuations in any engine , car or bike , is a leak in the induction/intake manifolds !
Try spraying WD40 or starting spray/gas in small amounts obviously on to the manifold when engine is running.
If engine speed alters every time you do this you have a leak !!