strange idle problem
 

I rebuilt my SC engine about 18 mths ago. It has run superbly since, except for an odd idle problem. Initially it was odd on warm start up - 5-10 minutes after shutting down. It would idle at about 1700 rpm for about 1-2 minutes, then back to normal at 8-900. Cold idle was 1200 and transition to warm was excellent. Everything else was running so well, I ignored it.
In the last few days - after adjusting valves and changing oil, I was idling it up to get oil level right, and idle suddenly died to about 3-400 rpm. Engine finally spluttered to stop. I had to wind the idle screw out a few turns to pick up enough idle speed , but it is idling lumpily now, instead of the dead smooth it previously had. And the warm start revs are now at 2000+ which is annoying.
The AAV is working fine.
Any ideas?
Alan

HI Alan L
check your oil filler cap is on correct and is sealing, with what you have described is a air leak in the breathing system??

regards mike

Have checked, and oil cap on securely. All a bit weird, but must be a reason. It was like it suddenly lost a cylinder. Except have just returned from a 500 mile trip and it is running very well at speed. Just a lumpy and sluggish idle with the idle screw wound almost right out.
Used to idle very smoothly.
Am about to pull the plugs out.
Alan