Of Valves and Stuck Pistons

Disassembled the valve train today and it came apart quite easily. I feared that the valves in the left cylinder would be frozen like the piston but they fell out without much effort.

The valve seat doesn't appear in bad shape and neither does the valve.

Now the frozen left piston is another matter. This past Wednesday I filled the cylinder with PB Blaster and let it sit till Friday afternoon, hoping it would free the piston. No such luck. So I tried it again and left the PB Blaster in till this morning. Repeatedly beating on the piston top with a 5lb hammer with first a block of wood cushioning (hoping to save the piston) and then a hardened steel drift pin had no effect but denting the piston top.

Evapo-Rust was suggested as a possible solvent to release the piston, but that requires the ambient temperature be 65 degrees, which my garage won't be on its own till June. Fired up the torpedo heater to warm the place up and filled the cylinder with Evapo-Rust and left it sit for 5 hours, and... The piston is still stuck in place. But the solvent did loosen much of the surface rust on the cylinder wall.

Earlier I had removed all the nuts and bolts retaining the cylinder to the crank case and raised the cylinder about 3/4" off the crank case, which shows that the crank will turn freely.

Not sure where to go with the piston. One thought is remove the crankcase and cylinder from the frame, which I'll be doing anyway, and then splitting the crank case and unbolting connecting rod.

Jim

Cylinder and Pistons

The needed tools to disassemble the cylinder head have been acquired and this will take place in the next couple of days. In the meantime, I've been trying to remove the cylinder from the crank case.

The left piston is rust-welded to the cylinder wall. Wednesday I filled the that cylinder with PB Blaster, hoping that it would free the piston. No such luck. I have removed the retaining nuts and bolts and freed the cylinder from the crank case and elevated it about an inch, where it is now supported by blocks and wedges. I spent about an hour today bang away at the piston with a 5lb mallet cushioned with a block of wood, but to no avail the piston is still stuck. Next I'm going to try an air chisel fitted with a drift pin to see if that can break the hold of the rust.

Lifting the cylinder off the crank case shows that at least the crank shaft will turn and that is not rusted solid.

I've been able to determine that I'm the 4th owner of this bike, recently I tracked down the original owner hoping he would take a bit of time to answer a few questions about the bike.

Readers familiar with Norton Commandos will not right away that the frame has been heavily modified to approximate the design of the legendary Norton Featherbed frame. Commenters at the AccessNorton forum expressed concern that about its rigidity, so this was a primary question that I had. The friend who I bought the Norton from, mentioned that the engine had been modified and I was curious as to if any light could be shed on the nature of the modifications.

The original owner and the person who completed the modifications is the owner of a well known manufacturer of motorcycle accessories. He told me that the frame works well and was stiffer than the stock Commando frame. He also gave me an overview of the motor.

It has been bored out to 906cc, the head ported and polished with big valves installed. The whole thing was balanced and blueprinted and built with light weight pistons and valve train. His recollection is that the motor was producing about 90hp and 75 ft/lb of torque when he had the bike.

Jim

Cylinder Head Off!

My how time fly's. Heat and the hand impact wrench persuaded the stubborn number one head bolt to release.

As you can see water gained access to the left cylinder with the result being rust and mold. Had a friend who does a restorations take a look at the head and his thoughts that it will clean up just fine, but he'd like to take a look at the valve seats.

Note the spark plug tip in the picture below, it was frozen in.

The left cylinder and piston do not look promising, but I expected to replace the cylinder body and pistons.

Valve caps and rocker covers are off in preparation for removing the valve gear. These areas appear to be clean and properly oily.

Note that the lower threads of the spark plug pictured below are filled with aluminum. Something else to be addressed.

Now to locate a valve spring compressing tool that will fit into this head.

Jim