3D Rave valve cut on 800R

[HPJUNKIE]

Wondering if anyone had their valves cut & what you experienced as far as differences in power delivery/driveability?

 

[Dmax.ca]

What do you mean by cut?

 

[HPJUNKIE]

What do you mean by cut?

Cut, as in removing material from the lower portion of the valves. This would effectively give you a larger exhaust port at the first two stages of the 3D valve. I'm not sure if when fully open, having the valves recessed further into their cavity would be detrimental or not? I'm sure the procedure would have pros/cons, depending on the usage of the sled. Simply doubling up the main mounting gasket would raise all valve components in unison, is this the best way? Thx for looking Dmax...

 

[Dmax.ca]

Not sure what goes on at other shops. But here we port the cylinder with the valve installed in the cylinder and locked fully open. This matches the valve shape to the port roof.

We have improved performance with a full cylinder and case port job but we've never tested just a valve cut?

 

[ak]

turbo al does this mod I have 2 friends that just had this mod done so I will get to try it out, Its suppose to give you more low end grunt.

 

[snowguthrie]

keep us posted on how it works.

 

[gus bohne]

some are cutting back the valve face to open the e port MORE with the valves down, this gives better power on the dyno under the point at which the valves are opening ( rpm window ).

others are pinning, (welding) the two piece to eliminate the multi stageing of the valve and just get the damn thing out of the way !!!


too bad ,,,the good old gas system just worked !! why we had to radius the wheel is unknown,, it was already round...

gus

 

[HPJUNKIE]

Thx for the replys Dmax/Gus! On the dyno it should show a gain @ lower throttle openings. I would also assume that it would help lessen the power on/off switch feeling when the valves whack fully open as commanded. Might be a benifit to deep powder tree boondockers? Thx again guys...

 

[ak]

Update,there does seem to be more low end And we need to add more pin weight because its over revin. I wish I had a stock sled to side by side test.

 

[gman086]

Cutting the valves opens them up which actually drops the low end grunt but gives better top end - bonus for mtn riders. Pinning the multi-stage valves together and blocking off the vacuum ports to make them gas activated does the same thing - they will open FASTER = cooler motor and more top end power (this works, been there, done that). If you want more low end torque/snap then use stock with the new longer/stiffer springs that BRP is now mandating for the '07 800R (the old ones were breaking). Same concept (stiffer spring; holds more pressure at low end) BJ uses in his trail torquer kits which are awesome for the flatlanders but not so much for the mtn riders.

My 2 cents,

G MAN

 

[gus bohne]

Update,there does seem to be more low end And we need to add more pin weight because its over revin. I wish I had a stock sled to side by side test.

Thats what I expected,, the valves are down too low and opening them at a stagger is EPA friendly not power advatageous..

dropped e port does make more low power buttttt,, when put in practice it actually reduces accell as the port is ONLY correct at idle..

the sub port fingers are the most guilty in this scenario..they block flow period, rather than lowering the actual timing.

piston to valve clearance is sooooo important to all of this ..

Gus

 

[ak]

well it does feel stronger and it was a fairly inexpensive mod. these were on 08 xp models and I dont know if the springs are different then the 07 800r motor.