Anyone "matched" their power valve?

[motopsycho87]

I've noticed that when the power valve is fully open, it actually closes the expansion chamber side of the head by about 5mm. Now I know that I can't remove that much material, but surely grinding as much away as possible and adding a radius at the end would be greatly beneficial? Going to do it at work monday, pictures and report to follow...

 

[gasgasman]

That's assuming the power valve actuator cycles open that much.

 

[Zman]

I believe the new valves have that curve built into it. I did perform the work you are describing on some of my older power valves that were originally square. I am not sure that i felt a real difference but every little bit helps.

 

[motopsycho87]

That's assuming the power valve actuator cycles open that much.

It pushes all the way to the stop, I've scribed a line on it in site, it's huge!

 

[motopsycho87]

I believe the new valves have that curve built into it. I did perform the work you are describing on some of my older power valves that were originally square. I am not sure that i felt a real difference but every little bit helps.

Good to hear!

 

[motopsycho87]

This is how much it overlaps at full open exhaust spigot side

 

[adriano.ro]

Hmmm,you will remove that part?

 

[Zman]

Watch out as you are grinding as you will get very close to the actuator slot in the flapper.

 

[motopsycho87]

I don't mind going through the hole a bit, there's a lot of meat there, as long as it's lubricated and supported it will work. Will grind the profile along the length to suit the port side, and the end to suit the outlet side. Means there will be a bit of a step when it's closed, but perfect when open

 

[TheLetterJ]

Hmmm... looks like one more place I'll have to give some attention to while my cylinder is off.

 

[Jakobi]

How are you going to get it to completely match?

Here are some pics from my 2013

 

[motopsycho87]

Has that got the valve in? Can't tell on my phone...

Here's mine after machining, I'll stick it in the bike and give it a try tonight. Much more flow than the brick wall that was there before though!

 

[Jakobi]

Looks good mate. Keen to hear the improvement. Mine still restricts the port a fair whack when wide open. I've considered shaving some off in the past.

Also, anyone tinkered with modifying the plate to extend range of movement? Either wider open or closed?

 

[motopsycho87]

Would you want it to open further? Clears the ports perfect on mine, and to close more surely you would turn down the OD of the stopper bolt or file the plate a little.

I'll get it back together tonight and put the old piston in, barrel is due for a replate, but I can drag it till the end of the year I think.

 

[motopsycho87]

Finished article matched to the spigot a bit better

 

[Capz85]

Looks a lot better

 

[motopsycho87]

Bike is back together, havent ridden it yet, but I've run it up, WOT seems to reach a higher ceiling than before, but the proof will be riding it to work tomorrow!

 

[motopsycho87]

Right, had a ride to work, so far it has increased over rev a decent noticeable amount. But the mid range feels like it's dropped slightly, will try altering the needle height and see how it affects it.

 

[stabak]

better flow means as like the valve opens quicker, right? The mid loss should be expected if the needle does not handle the transition accordingly...

 

[motopsycho87]

I haven't changed the height or anything, can only think the fact it staggered the tract might allow more or less fuel through, will take the bike to a local play area after work and try up and down one needle position