What causes the dip in my powerband?

[pandomar]

I went to dyno my bike, cause I wanted to know does the larger powe rvalve cover have any effect on power. I knew from previous tests, that my bikes power dips just before powe rvalve opens, but with the stock pv-cover on, the dip got steeper and when pv opens power increased allmost vertically. What is wrong? How can it be fixed?
larger pv-cover fixes the dip about 1hp while reducing overall low end power and torque..

[GGRider01]

I wonder if it's related to the powervalve timing? Could be a simple fix by adjusting the preload to open sooner.

[chrille79]

Originally Posted by pandomar

I went to dyno my bike, cause I wanted to know does the larger powe rvalve cover have any effect on power. I knew from previous tests, that my bikes power dips just before powe rvalve opens, but with the stock pv-cover on, the dip got steeper and when pv opens power increased allmost vertically. What is wrong? How can it be fixed?
larger pv-cover fixes the dip about 1hp while reducing overall low end power and torque..

I feel the same on my as the dyno example std gearing 6:th gear. Think this is normal.

50-70 km/h very strong
70-90 km/h slow
90-120 very very strong.

[pandomar]

Originally Posted by GGRider01

I wonder if it's related to the powervalve timing? Could be a simple fix by adjusting the preload to open sooner.

I have not adjusted pv before although I rebuild the engine once.. Preload is adjusted by shims? How many of those should be removed? I want get it right at first time if possible, cause the adjusting hasn't been made too easy in these older versions (11'). I was already planning to attach some adjuster spring to the right side of pv axle for easy adjustment,kind of like trusty pv adjuster, has anybody done anything like that?

[adriano.ro]

The blue line is stock pv cover? I have the same issue.

[celler]

On my 11 stock it was just like your experience. Dip with a big hit. I went in first and adjusted the power valve to take all the play out of my linkage. This help a lot but hit was still strong. I went to a NEDW needle that added more fuel so when the power valve opened it did not go lean first and then have the steep hit. The 11 was then very smooth and powerful.

I have an 05 that was the same way. Did the same as above but was not a smooth. I then went though and played with shims and ended up adding a little preload more than stock. No dip and hit but does have a flat spot, The power valve spring on the 05 is lighter so opens faster. I believe I need a stiffer spring so the power valve opens slightly slower. I have tried many combinations of jetting and preload and it is just not as smooth as the 11. This is my second bike that I do not ride much anymore so I have left it as is.

My conclusion is they open too fast creating the dip in power from lack of fuel.

[barossi73]

+1 the ne?? series needles(rm250) are much more linear than n1??/noz? which tend to go rich/burble then pretty much smack you with the full hit.straight swap also,jetting and clip the same,maybe bump pilot up one.use same diameter as the stock needle.noz? swaps direct with ned?,n1e? is half clip richer than noz?
nec? is halfclip leaner than ned?

[AZRickD]

I would expect a jetting problem, first.

Any exhaust gas analysis with that dyno?

[pandomar]

Originally Posted by AZRickD

I would expect a jetting problem, first.

Any exhaust gas analysis with that dyno?

No, just the hp figures. I have got the feeling that it runs little rich..