Ok,
I have stock valves with rw springs. How long on average does it take until a valve is shot from mushrooming??

So Stainless or Titanium valves of the same size done suffer from this?

I wonder if I should now replace my valves!?!?

 

Mudstud,

I wont happen for a while, but eventually those HD valve spring will take thier toll. BUT I talking Many many hours of riding before that happens. The stock valves are made good, so I dont think you need to change them. Ti valves would be considered a Modification cause them being lighter would allow your engine to turn higher Rpms longer, especailly coupled with stock Valve springs.





Bigger.

 

Here's my .02 on valve springs.

When an engine get's in the higher rpm range (7000+) stronger seat preassure in manditory. A weak spring will not allow the bucket to follow the down ramp of the cam after peak lift. This slam's the valve against the seat and causes it to bounce which bleeds off cylinder pressure (loss of power) and reaks havok on the valve, valve seat, springs, etc. It is my opinion that a weak spring will destroy the valve train quicker than heavy springs. Heavy spring pressure's keep valve timing more accurate and actually make more power even though they are harder to compress.


MrHorsepower

 

These are all good pionts, but How do we know that the Stock DS valve springs are "weak" ???

You have to admit that they are a pretty damn good springs already, it is VERY hard to push the valve springs down by hand, but on other machines(like the Rappy) you can push down the valve spring with out much effort with one thumb. I just dont think thier nessessary for stage 2 motors. But like someone said earlier , its hard NOT to put them in , for the money. I just dont like the idea of anything in my engine being Tight or binding.


Loose is fast[img]i/expressions/face-icon-small-smile.gif[/img]




Bigger.

 

Top engine builders today understand the trade off between a hard to compress valve spring versus a valve that does not seat properly. The consequences of a valve bouncing are more costly than the horsepower given up to stiffer springs. I used to build engines based on the light spring theory, but was convinced by a top engine builder to try the other way and saw real life performance gains! I have actually seen better valve train life too (although I thought that would be sacrificed).

222

 

I too agree that the Bomb valve springs seem heavier duty than aot of other oem's, which I've always considered odd since the bike has such a low rev limit. And I know plenty of people running high lift cams with stock springs and no ill effects.
I have heavy duty dual rate springs however, because I wanted the security of shim under bucket anyway and its all in one kit, even though I personally don't know if the springs are absolutely necesary for a stage 2 motor with a meer 11.5:1 compresison.

Now I know this topic is more concerned with springs than buckets, but I do have throw in that I think the aftermarket buckets in a shim under kit are lighter than the stock buckets. I haven't weighed them on a gram scale, but it seems I can feel the difference in hand, and that combined with the lighter titanium retainers these kits come with also are a plus, and top it all off with a shim that's less than 1/2 the size of a stock shim. This just brings you a step closer to lightening the valve trane, and the last step is Ti valves as mentioned earlier.