Riva Complete Exhaust Kit

Monday, April 28th, 2008
Replaces the restrictive sound suppression system located between the water box and hull exit on your watercraft. Improves engine performance by reducing back pressure and harmful detonation. Easy installation with noticeable results. Supplied Billet Exhaust Outlet also sold separately (part# RK16090-ET). NOTE: `08 Models require RIVA Pro-Series Water Box (part# RK16091). IJSBA Limited & Superstock legal.
So were can I start with this one.Lets start by what it all means for us 07 owners and 08 owners.
Starting with the 07 model. In early 07 Riva developed the free flow kit in which the second muffler was removed. This kit required one to cut a section of the tail pipe making reversing the mod difficult. Many of us continued on with it anyway. See write up here.
OK now that your back, lets continue on with the 08 model. In 08 Kawi opted to remove the second muffler and change the tail pipe diameter to a smaller outlet. They also opted to change location of outlet to the side that the second muffler was located. This change caused Riva to have to make a second free flow kit. So how do they do that? Well they had to open the free flow pipe up to the 07 diameter and make a new exhaust tip to match it. They also wanted to make a better water box to allow for tuners and performance minded guys the ability to have a less restrictive water box.
Here is pic of the 08 exhaust tail pipe routing, notice it location verses the 07.

Also notice the diameter change from 07 to 08. The larger in the photo is the 07 tail pipe.

Explaining why Kawi made the changes can only be speculated to cost savings and the new 3 star emission rating that the Ultra now carries verses 07 two star rating…….
So ya following me on the differences and the changes made between 07 an 08?
Now how does the Riva complete kit work together?
Lets start with he 07 group first. Now one can order the 07 Free flow kit alone, or with the Riva water box and the exhaust tip making complete kit that requires no modifications to stock parts. Its a direct fit and bolts together easily.
For 08 owners the complete kit is needed as the diameter changes to 07 spec with this kit. So the stock water box will not match to the Riva kit. This diameter change requires one to install the complete Riva kit for Free Flow on 08 models.
Alright lets get into the instructions. I’m leaving this up to Riva as they have done a simple an easy format to follow and I couldn’t find any better way of doing it. See link below. Yep I got Riva’s permission to post it.
OK here are some of my own photos to share.

The tail pipe tip that optional on 07 but needed for 08 models

Brass water fitting thats off the stock box. Be sure to install it as the pic shows. Notice how the water box has no weld other then the spun end caps. Riva did this to avoid water box damage from back fires and excessive back pressures caused by high end engine modifications.

The differences on the Riva kit exit and the 08 stock outlet

Again the size difference.

The above four pics are the way I installed my pipe section. It took just as long as the Riva instructed way. Still a different way to approach it.
Enough of that. Lets get into performance gains over the stock set up.
Speed gains were minimal if any but what was noticed is a similar performance gain to the popular but loud straight pipe set ups. The Riva kit cost more then a straight pipe but offer a quieter ride with similar performance.