Here is our new 30.5cc top end kit (I think it will be offered with the crank also). See the "for sale" section for the details.

Thanks folks.

Doug @ ESP

is this modified or stock?

Look above at the box. It says championship ported,so it is no way stock. To get to 30.5 cc you need a 2mm stroker crank.

There is quite a bit of work done.

1) The "Championship porting" is my high level porting (Compared to my cheaper "Race Porting on some other cylinders, which is down about .5hp and does not like to rev as far), and this porting is designed for boat racing with a 2mm crank. (only use a Zen crank with the 3rd bearing).

2) Head modifications,--The squish band is cut to accept the 2mm crank, and the resulting ultra high compression (from the stroked crank and squish band cut) is lowered by cutting the combustion chamber to a compression ratio we need (a bit higher for the boats, to help power in real bad air quality days)

3) The kit comes with 2 pistons (a RCMK piston with .020" longer piston skirts than Zen, and a Zenoah piston). Both are slightly relieved for piston crown expansion in cold water. The engine porting and head mods were built around the RCMK piston (and the longer skirts will not "free port" at the bottom of the exhaust port at TDC, like many 2mm builds do, if that is a concern for some users). But you can also use the Zen piston (both use the Zen ring and top rod end parts) which will give you 4 more degrees of intake duration for higher RPM power.

4) I use the .005" copper gasket to aid in transfer port time for the 2mm cranks.

5) I use the Zenoah G290 air cooled engines sealed 3rd crank shaft bearing, to help support the crank. We have twisted some 2mm cranks in the big 30.5cc with out the 3rd bearing. The sealed bearing replaces your stock large diameter crank shaft seal, and fits best on Zen cranks, as Zen lengthened the "bearing diameter" on the crank shaft on the drive side of the crank.

By the way, I don't sell stock engines or top end kits. My living is making stock Zen engines as fast as I can, and making sure you get a top quality product.

This kit currently holds a world record, as described in the DDM link below.

Here is the DDM link for the part number and description of this kit. (with out Zen 2mm crank)
www.davesmotors.com/cc275

The Zen 2mm Marine crank.
www.davesmotors.com/dd327


I have pics of the porting and head mods for a air cooled version (to give you a good idea of quality and work done in the cylinder), but can not post them for some reason.

Thank you all.

Doug @ ESP