YPVS powervalve

[jumjum01]

I bought a new set of powervalves from Legend motorcycles UK and put in my bike. Didnt measure them up before I installed them. But now when the valve is fully open the front lip/floor of the valve is not flush with the exhaust port (see picture). However the back is flush with the cylinder bore exhaust port roof. I found the to be important hp wise, when first adjusting the valve front lip to be flush with exhaust flange port. This made 52,78hp on the dyno. Then adjusting the valve to open "more" so the back lip was flush with cylinder bore exhaust port roof, that made 55,5 hp.
Dont know if these new powervalves have a different profile than the old OEM. But IMO the valve should be flush with both ex. port and cylinder ex. port roof at open position...

The questions now is:
- Will grinding the front powervalve lip to match the exhaust port roof make any gains?
- Will raising the exhaust port height 1-2mm in the cylinder bore and opening the powervalve to match the port make the bike rev higher and make more power?

[Yamavarna]

I’d think yes on both

[muttsnuts]

unfortunately the legend PV's are terrible, they require grinding to make them work correctly, I've had some lose 8bhp on a bike, on some I've had to grind 3mm off them to correct it

I've had some made by a firm local to me in Yorkshire, but they are more expensive than legends, but I designed/engineered out all of the problems the original Yamaha ones had and also some of the other after market ones available like these mentioned, they all seem to habve similar issues and all need work to correct them

I also had mine hard anodised so that they will last alot longer and less likely to wear at the joint, plus I had the bushes and end cap made, all out of top quality material, not some of the cheap horrible stuff coming out of China