Expansion chamber troubles

[genuineR50]

I have a genuine Roughhouse with a NCY 70cc kit, polini variator, and a 82 main jet also a polini exhaust. I recently put the new expansion exhaust NCY, which looks great but is horrible until about 40mph when it becomes very strong. But in normal riding I can rarely get to that speed with the NCY, I went all the way to a 95 main jet and worked my way back down with no help, I also staggered the roller weights with stock and the polini weights also no help. I finally give up and put the polini exhaust with everything mentioned earlier and it runs great all the way to 45 and pulls hills great. What do I do to make the expansion pipe I just paid $250 work?? Please help!!!

[aeroxbud]

It sounds like you need lighter rollers to get into the power band.
I have had a couple of exhausts that only make power in a small rpm range. They need carefully setting up to work well.
If your Polini is a street pipe, you will need stiffer clutch springs too.

[Zino]

Did you derestrict the ncy exhaust ?

[genuineR50]

No i have not derestricted it, i was unaware of the need to do so

[genuineR50]

is the restriction where it connects to the cylinder or in the muffler?

[Zino]

Check where it connects to the cylinder.
www.pedparts.co.uk/blog/yasuni-exhausts-how-to-derestrict

After you derestrict it be prepared to upjet