![evom lap valves evom lap valves](https://i.ytimg.com/vi/0JAKZ-dco7o/maxresdefault.jpg)
Lead as an additive was used to increase octane and allow higher compression engines. That brings us to the question of unleaded fuel. Our 450 DOHCs are already equipped with bronze guides.
![evom lap valves evom lap valves](https://www.moss-europe.co.uk/media/catalog/product/cache/1/image/1000x1000/9df78eab33525d08d6e5fb8d27136e95/c/m/cm0027pic1_2.jpg)
It is interesting to note, using a bronze bushed guide has better heat transferring properties than iron. First is the valve face and next is through the stem. Heat is carried away from the valve through two paths. The exhaust side lives in a much more hostile environment. Heat is the enemy of poppet valves in an IC engine. Valve "shortening" (to deal with valve extrusion) is generally not required except for 450 DOHC - engines with valve springs are not as sensitive to the extrusion issue. New seats, with new valves should require no lapping to get a good seal - my machinist refuses to lap in the first place, considering it to be a half-baked solution. Let's face it, materials have improved dramatically in fifty-plus years. My machinist does new seat installations on a lot of older auto engines suffering from the same problem, less commonly to our bikes due to the expense. Cutting new seats will give a good seal for now, but it won't last. Modern valve seat materials are incredibly hard and durable, obviating the need for Stellite in the first place.Įxperience demonstrates to me that most of these old bikes that I run into have valves and seats that look like your teeth would after drinking a gallon of Pepsi every day for twenty years - that's the effect of unleaded fuel, and it's the single most common issue I see with these engines. In any case, it is just a "coating" and would be removed by grinding, whether it's applied to the valves themselves or the valve seats (more likely). It's very difficult to machine, and is usually machined by grinding, rather than cutting.
![evom lap valves evom lap valves](https://2.bp.blogspot.com/-IwX46oSur2k/USEJeYz5BgI/AAAAAAAAPXo/bMiXX0QVJtE/s1600/2013-02-17+15.01.52.jpg)
As far as I know, Stellite can be applied by a variety of methods, welding among them.