Lapping those marks will just destroy the valve, I fear (but, it is probably already destroyed by the foreign matter). That should be recut.I did have one valve seat that looks lightly damaged and pitted like something got sucked through and was pinched by the valve a few dozen times before it left the engine. I am hoping that lapping the valves will smooth out the pitting.
I have the stock Mikunis from the original 750 engine. I think I went 165 main jet and 47.5 primary jet but thinking about that now, those might be too big. I have not decided on the air cleaner. I have the stock air cleaner box and I may try to put high flow filters inside or I may roll the dice and go pods. Pods are hit or miss and I do not want an unreliable bike. I may even try and build a new air box with pods inside.It is looking good.
What carbies are you using and where did you start with your jetting?
What air cleaners are you going to run?
I do not know how to figure out which Mikunis I have. There is very little writing on them. Does a picture help?You are definately going to have to go bigger than 750 stock, so I guess you have a starting point. If you do happen to find a set of carbies off a Triumph 900 triple they bolt staight on and I did not need to touch the jetting. Most people prefer the Keihin carbies but I found a set of the earlier Mikuni flatslides and rebuilt them for very little cost.
Do you know which version of Mikunis you have? The later version are supposed to be better than the first version and the Hitachi used on the 850 are to be avoided due to difficulty in getting parts.
Once you get this bike going you will not regret the work. The 896 bigbore transforms the bike from average to whow! The only problem is you run out of gears at 200Km/h, if that really is a problem!!!!