What Grotto said.

However, another great solution is to use one of Joe's excellent YS exhaust adapters that convert the YS bolt on header to a "spring on" NovaRossi header. The adapter is much like those used on OS engines such as the Hanno, the RF/VF series before that and the NR SE engines today. It's a flat to round nozzle adapter which has a silicone rand on it. The round inlet header is then seated against the rand and held against it with a spring which wraps around the cylinder - effectively a soft mount header.

splitting the header might still be needed if the engine is vibrating considerably in the soft mount to avoid stressing the header/pipe junction directly.

A side benefit is that exhaust flow (and power) is improved as Joe matched the adapter inlet to the YS exhaust outlet; something which Hatori and Macs for some reason failed to do.

See this thread for details:

https://www.rcgroups.com/forums/show...xhaust-adapter

Adapter/header kits are available from Leo Steck here:

http://klasskotemo.com/

I added some pics to show the adapters and the similar concept used by NR on their SE engines (the RE engines have the nozzle cast into the case). The last OPS engine shows their adjustable tuned length exhaust header. The pipe slides into the header allowing for a variable length. While this can't be done with the NR headers (unless modified), it shows the concept of using a "stub" header at the engine attached to the main header via a coupler (OS used this system too on their RE engines as mentioned above). If one uses the same idea as described by Grotto with the NR header cutting it close to the adapter junction and dual couplers, the result is a built in "soft" mount for the exhaust. One can even hard mount the pipe with this setup. However, with the spring mounted header, dual couplers and cutting the header at the root should be unnecessary.

David