Saving Old Seagulls

Hello all. I have, under my wing, a QB Osprey which has been misbehaving. It ran OK for five minutes or so, then the revs started fluctuating then finally stopped and would not re start. There seemed to be a reasonably healthy spark straight after the motor stopped, but it would not re start. Five minutes later it would start again and then repeat its performance. Having had similar symptoms with my FP, I thought the head gasket may have blown. Fitted new head gasket, and all seemed well. Ran the engine in gear, in a large test tank. After 20 minutes or so, intermittent misfires, then ran perfectly for a minute or so, then just stopped dead, like it had been switched off. Not a glimmer of a spark. Leave for a few minutes, sparks re appear, starts and runs roughly, sometimes as though someone's pushing the kill button for a second, then releasing it again, engine dies again, no sparks.
Plug is OK, new plug cap, isolated kill switch, so it's not that. Insulation looks ok on kill switch wire and there is no continuity with earth. I suspect the ( very expensive ) CDI, but would like to replace the HT lead first, to make sure it's not that.
Two questions, the HT lead seems very securely fastened into the coil, how do I get it out? Secondly can I test the CDI unit with a multi meter? I am getting some strange continuity readings , I assume this is something to do with the electronics in the unit.
Any advice on the above would be much appreciated, thanks in anticipation,
Andy.

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the charge coil ( nothing to do with battery charging) produces about 400v which charges a capacitor...this is discharged into the coil by the electronics...continuity is not done ....you measure the output voltage from the charge coil whilst cranking or trying to start it ...if the voltage is out you replace the unit....ha ha ....there is a circuit from silicon chip called Replacement CDI module for small motors ...have a look at

http//www.siliconchip.com.au/cms/A_110499/article.html

If you can type that right you can make one for peanut money !!

there is a full explanation of how it works in the article

If you can type that right .........

Put a colon in the right place and it'll convertitself into a clickable link

http://www.siliconchip.com.au/cms/A_110499/article.html