1968 BSA B25 Starfire top end

About a year ago a good friend set me up with a seized baby beeza. It looked pretty cool with ace bars and being a single it got my mind going.  However, it was sidelined for a time as other projects were in front of it.

With a lull brought on by the winter weather I started to focus on projects that had been hanging around cluttering the workshop. Going down the list, many of the projected machines still lacked parts to complete before spring. The only two viable machines were the S90 Honda in bits and the complete B25 with a stuck engine.

So ripping the top end off the BSA to find why seemed the easiest action. It was in fact, relatively easy.  Withe the exception of the proper wrench for the head nuts.  No matter where I looked I couldn't find the right size. So with a cheap Chinese 14mm and a hand file, I set about making a 'fitted' wrench.

The reason for the seizure; storage in a damp or humid environment. There were tell tail signs of water condensation internally.

The rings had corroded into the ring lands. The wrist pin was quite stuck making extraction slow and difficult. Many heat cycles and a screw press finally removed it.

  After cleaning up the lands and giving a quick break to the glaze in the cylinder the original piston would still be usable.  There was some staining on the barrel however, the piston and barrel were in spec.  The whole engine should be redone but not having tools on hand, the extra cost on an unproven bike and the overall time I decided to make it work.

The bore was cleaned up, the wrist pin was replaced and a new set of rings installed. Oil flow to the big was tested, as was oil flow to the rockers.  The engine has 4700 mile on it so we'll see how it sounds and runs for a bit before a big teardown.

Here are a  few pictures of the original pistons before it was cleaned up and reused. 

One of the fun things was hand making the paper gaskets needed to keep this a simple job.  Yet a task to challenge oneself; what would one do in the middle of nowhere...

Reassembly was mostly straight forward. The biggest trick was getting the pushrods into the proper positions and keeping them there. Even then after checking and testing and double checking they still were tricky.

Once the head was installed it needed a quick check to make sure the rockers were getting their fair share of the oiling.