I’ve stripped and cleaned the carb. Nothing evident anywhere other than the main channel though the middle (and of course - the slide). Not oval - it all slides very nicely again. Nothing in the float bowl, pipe, jets etc.
Evaporated fuel leaves no trace.
I’ve drained the tank anyway and also spoke to a very helpful chap at Tank Care Products (the liner maker). Swear blind that the liner is good for 100% ethanol, so clearly able to handle the 5% stuff I’m feeding it.
All I can really do is stick is all back on (no pun intended) and see if it happens again. I think I’ll ‘feel’ it this time if the throttle starts sticking again - so I can stop before it all gets amusing.
I’ll leave the rubber air filter hose off for now as suggested and hope it doesn’t suck any passing children or animals into the open carb mouth.
Is your air filter the one with the louvres at the front, near the magneto? Did you spray the magneto with WD40 shortly before the trouble started?
When it dries out after a long time, WD40 becomes a sticky goo. If the fumes from it had gone into the air cleaner and then been drawn into the carb, perhaps this could be what you are seeing.
Paul Jameson
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
I like your thinking, but no WD anywhere near there (converted it to electronic ignition so all sealed in). But…. You may have something. I wonder if I over-oiled the air filter gauze thing, and oily goo air has been sucked in somehow (hence the black layer on the intake bell mouth side of the main throat).
I do use the filter element on my KH but don't oil the filter element directly. What I do is wash it in 2-stroke mixture which gets a minimal amount of oil on the bits of the element, but enough to do what is required.
Paul Jameson
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
I think you have found your problem. You should always squeeze excess oil out from the element. Thick filter oil is not for anything other than the filter. Nev
A further way to "oil" the element is to dissolve some grease in petrol and place the element in it and then allow it to dry. Then you'll have a very thin layer of grease on each strand of the element that won't blow off into the carb. I use this on all my home made air cleaners, especially those for my compressors where I most certainly don't want contaminated air.
Regards from MikeN.
PS I make my aircleaner elements from "Spontex Heavy Duty Scourer Pads" (available from all good supermarkets).
Great discussion chaps - thank you. Have cleaned out the carb, sorted the filter element (just in case) and brimmed the tank. Will do a further mixture check (it may be a bit rich - I get a bit of ‘Rev hang’ when changing gear at slightly higher revs), and the exhaust are slightly sooty - so will also recheck the timing to make sure it’s spot on too (when it’s hot it spits once or twice at tickover). All in all, a bit of fettling still to be done to make it supper smooth, but at c.50mph in too, it lopes along very smoothly and the ride is surprisingly stable/neutral/enjoyable.