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In the course of tuning RZ350s over many years, we oft lamented the poor fitment of stock Yamaha YPVS valves (top picture, at left) which, as you can see, do not match the corner radii of the exhaust port very well at all.
This power-valve/exhaust port mismatch naturally creates turbulence and slows down the gas flow.
The bottom picture shows the snug fitment of TSS Billet YPVS valves - note how the valve blends flush with the exhaust port/cylinder casting.
Naturally, this sweeter alignment brings power and efficiency benefits:
> Smoother, more laminar gas flow = more HP and torque |
> Better effectiveness of the power-valves because of the snug valve fit all the way across the port; manifesting in stronger low-end and midrange power |
> Valves are made of 6061 alloy, hewn from solid, which is a lot stronger and more wear-resistant than the porous cast generic alloy Yamaha uses in the valves. This is particularly valuable with regard to the centre joint faces, which tend to round off quickly in the case of the softer, more porous cast Yam valves. |
> The TSS power-valves are super-slick and smooth. Again, better for gas flow, and the smoother surfaces are better able to resist carbon-build up |
TSS Billet YPVS Valves:
Available in two different types:
>>> For RD/RZ350 (31K/48H) - 1983 - 1985
(Also for 29K, 35G, 33E, 31K, 31W, 48H, 52Y,
33E, 1EL, 1AH, 1AG, 1JF, 1JG, 57V, 1AF)
>>> For RD/RZ350 (1UA/1WT) - 1986 - on
(Also for 1XA, 1XE, 1WT, 1WU, 1WW, 1WX, 1WV, 1WY,
2UA, 1YH, 3DH, 3DJ, 3DK, 4CD, 4CE, 4CD)
We also noted with disappointment that Yamaha has only ever produced powervalves to fit the early 31K/48H cylinders - and not the later 1986-on 1UA/1WT cylinders, which have a 0.8mm higher exhaust port roof.
Naturally, this means that powervalves designed to fit 31K/48H cylinders will have at least a 0.8mm alignment error; i.e. if the valve's working face is flush on the cylinder side, then it will necessarily be protruding in a step on the exhaust side - creating turbulence and impeding engine efficiency.
Or, if the valve is flush on the exhaust side, it will be 0.8mm down on the cylinder side - which will effectively lower the exhaust port height and prevent the engine from reaching its power potential. Either way, the valves do not fit the application properly, and any potential for extra power in view of the higher exhaust port is negated by the compromised valve design.
With this in mind, we designed and tested two carefully-matched billet powervalve designs: for both the 31K/48H cylinder and the 1UA/1WT cylinders.
Both of these types of valves are in stock and available now - at a very affordable price of USD$130 per full set (for both cylinders - all four segments) INCLUDING shipping anywhere in the world.
You can pay with Paypal, below:
Buy Now: TSS Billet YPVS Valves for RD/RZ350 (31K/48H) - 1983 - 1985 (Also for 29K, 35G, 33E, 31K, 31W, 48H, 52Y,
33E, 1EL, 1AH, 1AG, 1JF, 1JG, 57V, 1AF) (Including Shipping Worldwide): USD$130
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Buy Now: TSS Billet YPVS Valves for RD/RZ350 (1UA/1WT) - 1986 - on (Also for 1XA, 1XE, 1WT, 1WU, 1WW, 1WX, 1WV, 1WY, 2UA, 1YH, 3DH, 3DJ, 3DK, 4CD, 4CE, 4CD) (Including Shipping Worldwide): USD$130
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Otherwise, payment via secure gateway, here:
Buy Now: TSS Billet YPVS Valves for RD/RZ350 (31K/48H) - 1983 - 1985 (Including Shipping Worldwide): USD$130
(Also for 29K, 35G, 33E, 31K, 31W, 48H, 52Y, 33E, 1EL, 1AH, 1AG, 1JF, 1JG, 57V, 1AF)
Buy Now: TSS Billet YPVS Valves for RD/RZ350 (1UA/1WT) - 1986 - on (Including Shipping Worldwide: USD$130
(Also for 29K, 35G, 33E, 31K, 31W, 48H, 52Y,
33E, 1EL, 1AH, 1AG, 1JF, 1JG, 57V, 1AF)
Any queries? For more info, such as costs for multiple orders, please feel free to contact Steve and Wayne of TSS:
Email 1: info@twostrokeshop.com
Alternate Email 2: offbeat@iinet.net.au
Alternate Email 3: bikes@bikingaustralia.com
Alternate Email 4: info@offbeatrips.com
Tel. (In Australia): 0427 774 285
Tel. (Outside Australia): +61 427 774 285
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Stock Yamaha YPVS Fitment: RD/RZ350 (31K/48H) 
