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[Wheaters]

The gas flow in that head must be very poor, especially on the exhaust stroke. Cutting the seats back will reduce compression slightly but should certainly improve the power output. The protruding lip will cause turbulence and make the valve act as if it’s smaller than it really is.

[Allanfox]

I know you weren't proposing this, but if you start experimenting with sportier cams, you'd quite likely have to cut a little valve pocket in the piston crown. If the valves are in the right place to start with, less material would need to be removed from the piston crown.

A.

I do like the bike (going off it!!!) and just want to get a few thousand miles on it first before any real attempt at tuning or modification, just be nice to set off with some hope of getting back!

[Allanfox]

The gas flow in that head must be very poor, especially on the exhaust stroke. Cutting the seats back will reduce compression slightly but should certainly improve the power output. The protruding lip will cause turbulence and make the valve act as if it’s smaller than it really is.

Yes my thoughts too, really can't be very effective like it is. If I cut it back all the way to the head I don't think the seats would still be big enough, they flare out and cutting it right back would pretty much chop the flared bit off, it's almost like they are just not deep enough in the head and need pressing in further before cutting and lapping in, In wonder if that is the problem and just poor manufacture/QA? Can't see how this is an intended design?

[Wheaters]

A good engine shop should be able to sort it out, cutting further down into the head casting if need be, to allow a full depth seat to be fitted.

[Allanfox]

A good engine shop should be able to sort it out, cutting further down into the head casting if need be, to allow a full depth seat to be fitted.

Luckily enough I have a few good ones near me in Suffolk that specialise in bike work, off we go!