The DT (175mx) has had a rebuild, (crank, piston etc) and ran fine for about half hour then lost power a bit and struggled to accelerate, I ran it like that for a few minutes so don't think it was mechanical, seizing etc. Anyway, checked the plug, OK, so had it out today (20mins) and it ran fine! So although the carb floods a bit I don't think it was that cos I ran it with the tap off to see if it would clear and it made no difference. So , can the coil breakdown when hot and cause similar symptoms ? I've checked the resistance values and they match the spares I have but obviously it's cold now so not sure how to check, any clues good people, Dave

Aye dave "  its illimination process . swap the coil,  then points/ condencer, how does it idle when warm ?

Hi John, I hope you're well and managing to dodge the showers!  Had it out again and still ran fine for 20 mins or so, then a puncture and no spare so will try again at the w/e. There's no points etc,some sort of electronic thing, checked with a tdc gauge so fairly accurate. all i did was shorten the HT lead 10mm and re-fitted the plug cap and so far so good.

It does idle a bit high when warm but assume thats just a bit of throttle slide wear ? Thanks, Dave