Apples to oranges

Looking twice as big the Simonini exhaust system is only ~2 kg heavier than the old one.

Knowing very little myself about 2 stroke engine performances in relation to exhaust systems I have tried to find out, mainly through the web, how it works.

Here is the short version (for the long version Google “tuned exhaust system”...):
The exhaust, forming a wave, start by going down the pipe and then - during the same cycle - bounces on the back wall and goes backwards pushing fresh mixture back into the cylinder. 

Click the picture to see the animation
(Source http://www.southernskies.net/page_info/runningtwostrokeengine.html)

I.e. each cylinder need an individual exhaust system and anything looking like a “Y” should be banned...
To get maximum benefit from this wave movement the exhaust system need to be “tuned” in terms of volume, length and shape. 
Forget cutting a bit and adding another bend to squeeze in the exhaust system under the hood. Doing that will inevitably reduce performance.

No more dripping rotary valve oil

You know the rotary valve lubrication circuit on the Rotax 532/582, the one that is always leaking from either the container cap and/or the tubing?

Well, Victor has no rotary valve so there is one pain gone away...

Remodelling the engine mount

The modification of the engine mount simulated with bungee cords. 

The ignition coils (normally fitted on the rear engine cover plate) will have to be moved.  I removed the cover plate to get more room for the engine mount (I don’t want to move the engine forward if it can be avoided). As the engine is already protected by the firewall I will replace the cover plate with a more minimalistic protection for the water pump belt, I will gain almost a 1 kg...

My current engine mount will not fit without modifications

With the starter on one side and water pump on the other the Simonini engine is wider in the back than my old 532.  To make it fit I will have to modify the 2 lower “legs” of the engine mount.  

... but as long as the engine is fitted in the same position as the 532 the propeller axis will come out at exactly the same place and distance according to my measurements.

The engine finally arrived this morning!

So, does it roar like an Italian tigress, consume only 8l/h and run smoothly for 600 hours until the next overhaul? 

You have to wait a little, I have barely opened the box... Very well packed, one wooden crate with just the engine and a cardboard box with the impressive twin exhaust system, 2 Bing carburettors and filters, a 50 page Operators manual (in English) and some extra stuff I bought for the installation. 

Still in the box the engine looks big and I wonder if it will fit my current engine mount... That will be the first thing to find out.