the WP spring I’m using is from early EXC model
Yamaha OE spring dimensions. Length 216mm. Top diameter 59mm. Bottom diameter 54.9mm
The WP spring I’m using Length 220mm. Top diameter 61.7mm. Bottom diameter 59mm.
discontinued racetech length. 222mm. Top diameter 61.2mm Bottom diameter 56.5
I’m think you could use as is but I made two sleeves to ensure everything stays centred.
The spring I’m using is 85Nm but there is a huge range available.
I’ll let you know how it goes tomorrow.