Step 7: "Puke tank", seat, and engine mounting.
Next, I decided to machine slots into the engine mounting pan. I made keyhole shaped slots that enable the engine to be slid forwards and back so that the chain can be fitted and tensioned properly. This is the longest chain on the build, thus a spring-loaded tensioner was fabricated in addition. Since the chain here is hanging horizontally, you want to have constant, gentle pressure applies to keep it from falling off. The tensioner is simple, using a channeled nylon idle pulley typically used on mower decks. Like the skateboard wheel, nylon holds up just fin on chain. The pulley is mounted to a arm that is bolted to the underside of the simulated mower deck via a nylock nut and bolt. A spring is attached to it as well as a bolt welded to the underside of the engine pan. As you can see, the chain fits nicely from the centrifugal clutch to the RAGB.
Now the seat. This step is actually kind of important. You'll find that staying on these mowers on a bumpy dirt track with sharp corners is difficult.The inertia will threaten to throw you off. But at the same time, if you do fly off, you want to clear the "scene of the accident" and not get run over by your own mower. So it needs to be low. The solution is to have a low seat with low sides that keeps your rear attached to the seat. It'll actually give you more control. One last word- it helps to have padding. A steel seat with no padding can be... painful. My Wife covered mine with upholstery from an old chair.