Sprocatti MHR Big Bore
The long promised update. It's been a long day's work! But it has finally been finished; at least the main course was: fitting the crankshaft into the crankcase. The cylinder is a direct fit, just needs some base gaskets-adjustment to properly fit on to the engine.
The crankcases were a right bitch.... Honestly. This is exactly what I expected, but I hoped it were not to be the case. The cases fitted on to each other perfectly, but when they did, they were too tight. The crankshaft simply didn't turn freely. It needed too much force to pull through.
It was clear; a case gasket was needed. Obviously these don't come stock, so time to break out the cutting board gear and custom fit two gaskets.
You might say: Isn't that obvious? Well no, it isn't. Usually the aftermarket crankcases should take into account the extra clearance needed for the crankshaft, but let's face it, it's not a Polini or Malossi case where everthing is fucking prefect. Custom crankcases need custom work. So stop bitching. This is one of the best engines out for Piaggio / Vespa. No faith? Then go fuck yourself...
I custom cut some case gaskets to fit the crankcases and the job was done. It took an hour or two; better safe than sorry. The engine fit together like a charm after fitting the gaskets. The crankshaft moved freely and all was well.
As we have mentioned before, this engine will be started via a kickstart system. We have pearl blasted a kickstart pinion and totally rebuilt it (with a new HK 1514 bearing). It now moves smoothly.
It still does not fit on the engine proplerly. The Sprocatti engine's crankshaft still sticks out about 3 to 4mm too much. We will soon be milling a new adaptor piece for the kickstart adjustment. We can simply place rings to make up for the space, but let's be honest, how lame is that? We wouldn't be MOPARTS RACING if we weren't the best, right?
Now drool at some pics:
Look how close that crankshaft runs through the casket/inlet housing. It's a millimeter of clearance, tops.. (roughly 3/64 inch for my American friends)...