My Engine choice for my Pilot was a Engine that is 25+ years old, they are pretty
easy to find if your not in a hurry so I picked up a few spares on Ebay, both need
new crank seals so I figure now is a good time to replace the seals and clean up
the casting flaws on the cases and cylinders.

The cases are pretty rough in stock form, casting flash every where, I set the cylinders on the
cases then scribe the areas on the cases where they need matched, you can see in the picture
the miss match is huge, I wish I had a 340cc cylinder it is almost like this case was cast for
340 cylinders not 440, or both, you can put 440 cylinders on a 340 bottom end or 340 on a
440 bottom end...

Here is a after pic

Bottom side

The cylinders needs lots of work the castings have flaws all over them, I spent
about 3 hrs just roughing this one in there is at least 2 more hrs left to rough in
then who knows how many hrs doing the final tweaking to balance things out.

You should take one of your spare bottom ends and fill the bottom with a fill or a wedge. By reducing the volume in the bottom end it allows for much higher intake pressure which results in more power. I tried this on a 100cc two cycle go cart Engine and it made a huge improvment in throttle response. I used an aluminum wedge in that application. I am curious as to the results in a twin or triple cylinder application. Just a thought I've been toying with if Brooks ever has me put that 617 rotax in his pilot.

There is not alot of room for stuffing in these cases, the windage trays also aid in
reducing the volume.

More pics http://pilotodyssey.com/440mold.htm

And http://pilotodyssey.com/440cylinder.htm