I built the engine for Rhino some years back using the crankshaft and main bearings from a seized engine. I got hold of some nearly new nickasil coated barrels with pistons and changed the big ends. However this was during a time when I wasn’t very well and I cut some corners. So this is the first of two posts on putting right my mistakes.
I remembered that, when it came to fitting the barrels, I hadn’t got the necessary O rings for the cylinder studs. So, I went to my stock on the shelf and fitted what looked right. I felt (rightly as it turned out) uneasy about this so the barrels had to come off. I started with the right hand cylinder. When I removed the cylinder head this is what I found.
The piston is the wrong way round. The arrow on the piston should point forward so that the valve cut out corresponds with the inlet valve which is bigger than the exhaust. Luckily the engine had not been run but only turned over by hand when all had seemed ok. I carefully pulled the barrel off without letting the pistons go “donk” onto the mounting studs. The base gasket was broken and the O rings squeezed out over the top as they clearly had been too big. I heated the piston up with the hot air gun and managed to push the gudgeon pins out without having to resort to using heavy handed methods. I put the pin in the freezer, heated the piston again and swapped it round the right way. Barrels on with the correct O rings in the right places and
That’s better. However, I made a basic error ordering parts. The head gasket should be like the old one above but it was like this
The holes for the pushrod tunnels don’t line up. As soon as I plopped the gasket on I knew what was up. Early big block Guzzis have the holes closer to the cylinder bore than later ones. I think Guzzi relocated them to make room for the bigger bores of the proposed 1000 (949cc) engine. I have proper V7Sport barrels and heads. Replacement gaskets were ordered from Gutsibits and arrived in the post the following day.Threw the rest of it back together and here we are with the valves adjusted and almost ready for the other side.
The O rings and gaskets were in the same state on the left side but at least the piston was the right way round this time.