[09viewlake]

SORTED!!! Well, the ebay spark plug turned up today so it was time to get frozen again in the shed! Laid the plug on the head after putting it in the plug holder, pulled the starter and bags of sparks. Screwed it into the head, turned on the juice, tickled the carb and on first pull it roared into life! ....then started to slow so I opened the throttle more and more and it continued to slow to a stop . Aaaargh! Took plug out and was sooty (ie juice present). Laid on head and pulled starter - got good sparks BUT it felt like the plug was still in. Tried to turn the crank by hand - very stiff! Then my 50 years of motorcycling experience kicked in! This felt like archetypal 'tightening' of the engine prior to seizing - but this engine is 30 years old - not just rebuilt (as far as I know!). Ok, WD40 in the plug hole and the engine spun easily on the starter - conclusion: under load the piston was starting to seize in the bore. Ok, lets put a whole lot more oil in the crankcase despite the fact that it was up to the mark on the dip stick. Fingers crossed, pulled on the starter and it fired up again - and STAYED RUNNING  Opened/closed the throttle, played tunes on it for 15 mins or so and then settled it down to a nice, regular tickover - and there it stayed. Stopped it and went back again 30 mins later and it fired up easily again.  Soooo...what was the problem? TOO LITTLE OIL!!! I have spent the last 18 months, on and off, looking at the wrong things!
Now the dipstick can sit at two heights (yes, really!). If you pinch the ringed top together as you push it in it goes right down to the finger-pull ring. BUT if you just let it drop in it stops where the dip stick splits in two - a good 1.5 ins higher therefore more oil in the crankcase. You need at least to use this level to avoid the problem I ran in to. :happy:

[Yorkie]

Good detective work there 

[jezza]

hi try 4thou of an inch for  gap  you should be able to change the HT lead (sparkplug lead)they used to be screw in on suffolks jezza