919 fork piston mods.....
I have left over from when I had my 919 a pair of comp pistons. Having spent so time since then mucking about with these fork carts in my other bikes I decided to mod some 919 ones for Kiwiboy. I spoke to him about this ages ago but only got round to it today.
So the first pic is the stock pistons. Pretty much as I can make out they run 1.6mm ports for the comp side. Tiny compared to anything else I have worked on. They have a basic shim stack of 4 shims.
As an experiment I have taken the ports out to 2mm although I may see if I have a 2.1 drill. 2.5 is to close to the sealing edge for my liking. Added a small taper on the top side of the ports. I also ground a approx 1.5mm port as a low speed bleed and to help the high speed. This was nothing like as tidy as I would like so if this works out for the next one I will drill a bleed in the cart body as per Roger Ditchfields "Rogering" mod.
I will give this to Kiwiboy and tell him to run 5w oil. If it works and I think it will he will owe me 2 coffees when we go out for a ride with my beloved. If it doesnt I will pay for the fork oil to swap it back.