Helmholtz resonators are often used on header pipes like that to help smooth out the power curve. Since the pressure waves of the exhaust travel at nearly the speed of sound (basically a fixed velocity), and the exhaust pipe is a fixed length, certain RPM ranges have imperfect harmonics which cause dips in power due to a loss in scavenging - meaning that the timing is the only variable. By adding a resonance chamber to the header pipe, it can help to decrease the intensity of the pressure waves, and smooth out the power curve. Not really meant for more power, but better overall power.

It is also often used on intake pipe systems to help eliminate "bad" resonance wave point and smooth out airflow. Or even simply used to reduce resonance noise.

Harmonics and Resonance waves are one of my weird hobbies lol.

In the case of this pipe, it may actually serve some benefit, but more than likely nothing to write home about. There are a lot of variables at play that can completely change the locations, size, shape, inlet area and length of the chamber, that unless it is specifically designed and built for a particular engine, with a particular cam profile, to a specific pipe length (Node and anode relationship) , and then desired affected RPM range, it is likely not going to do a whole lot of anything useful. It may alter the sound a bit though, which is possibly why it is there...or simply for looks.

I really like the battery and solenoid relocation. I have a Chonda dirt bike build on the back burner, and I think I'll borrow your idea.

Test ride day!!
 

Took a day trip out to test the mods out. Fabulous day of 50+ miles of mostly single track!! The new tank really makes the bike handle well. On steep climbs I can get my weight forward and it's much easier than it used to be.

Motor ran well. Have to get used to how low-end centric she is. Short shifting all day.


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No appologies dan

"Harmonics and Resonance waves are one of my weird hobbies lol."

I think I remember a few labs from college. :hmm: Physics is fun.

Good stuff CHONDA, I see your spring time in Idaho is coming along nicely.

That tank looks really good on there. I think that NC250 spoiled you to high rpm power though. Welcome back to the grunty side of things.

A little video from our day yesterday!
 

Yes Dan!! I had to re-learn how to short shift this bike!! Whole different animal.

Enjoy:
https://youtu.be/S8VPRdnOxHE

Another vid
 

Kind of gives an idea of the terrain we get into at times. :hi:
A brush with a tree knocked the camera angle down too far; it get better at the end.

https://youtu.be/QS4ALnVZqSs