Just spoke to the shop and they said they had done a crankcase pressure test which resulted in oil being pushed up into cylinder 3 which would be causing intermittent miss fire and it definitely needs new piston rings. Cost likely to be 6 hrs labour at £60 per hour. £150 for new gaskets and £150 for Piston Rings. Plus £108 already spent. £768 +vat.
Oh yes they're conning you, what utter bollocks.
When you do a crankcase pressure test, all you can do without stripping the engine first is tell that compression is being lost to the crankcase, because the compression rings/bores are worn or stuck. Lack of compression on it's own doesn't give you misfires just lack of performance, leaking valves will give you a misfire, but on a bike with only 40k it's very unlikely if that is the true mileage. I've worked on these bikes since they were introduced and in all that time I've seen only a handful that have suffered lost compression and required major rebuild work and these were badly abused 60k plus bikes your is 40K. Let's assume for a minute they're right just changing the rings wont solve the issue, if the rings are buggered so will be the bores and most likely the pistons.
Your readings of 15 & 12 are within spec, I'm pretty certain your misfire has nothing to do with your engine. The carbs are your issue, mostly they just need cleaning out of the pilot circuit, which is easy but as with everything it's easy when you know how!
Mate change your dealer now.
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