minor dip in the powerband

[pandomar]

My bike is 2011 ec 300. Carb jets: main 175, idle 45, needle N1EG (circlip on second groove from the top). I use 0,5mm cylinder base gasket. There is a dip in powerband just before pipey section, what causes that? Here's a dyno chart with both ignition maps, the revs aren't right

[AZRickD]

Maybe a little lean when first coming onto the needle.

How does it feel when you ride it ?

[Jakobi]

Appears to be related to the PV duration/timing from the dyno data.

Possible that the PV is either not opening soon enough which causes the power to flatten out and sign off until it opens and allows more flow, or could be the other scenario in which the PV opens too soon and the engine has to catch up before it comes onto the pipe again.

In saying that though, is there any reason why the curve is signing off with peak power only at 5500rpm? You'd expect it to be up around 8000-8500rpm.

Edit: Found some information provided by Dave at TSP when he was modifying the head to match the S3 Race ported cylinder.

Another issue with the EC250 is that the fact that the powervalve snaps open very fast causing a drop in the mid range with the larger exhaust port... if you could keep the same opening start point (about 4500) but extend the opening period out to 7000+ rpm (currently fully open by ~6000) it would work better with the bigger ports... this is obvious in this graph how the GREEN line doesnt drop at all at 6500 but the other two do... its timed to work with the smaller stock ports.

[pandomar]

When riding it feels like the rev transition to pipe, is a bit "edgy". We did not sync rev with the dynamometer, so the curve is actually time vs hp. I suspected the PV myself, but its hard to tell is it too late or soon (if I only had outer adjuster on pv..) I used to use 2 cylinder base gaskets 0,5mm and the green one. Now I only use one 0,5mm thick gasket in pursue of more low en grunt, it effects to PV but not tihs much?

[motopsycho87]

How does your bike act on constant throttle at this rev range? Does it sputter and struggle? If so it may be too rich. If it just feels weak and 'fluffy' it may be too lean. If it feels like it hits a wall until the power valve opens, it may be PV timing.

[Capz85]

Did they use an afr at the dyno?

What was the wheel hp?

[webmaster]

The n1e series needles are horrible. It will typically clear out as you transition fully on to the main.

Squish is typically not within spec either.

Dial in the squish band by having the head machined and fix the jetting....

For those in the u.s. I recommend rb designs for head machining. He also offers carb mods.

Jeff