BWM 250 restoration progress

Well, this engine will also get the big bath treatment and then we'll decide where to start with him.

OK, so now we will start with cleaning up the case and back plate, also polishing the cylinder head. We will keep the original anodized finish on the case as it's actually in pretty good nick. Here's the progress to date.

Now its onto making the new crankshaft and prop shaft.

Test fit to make sure all's well...........

Loverly fit and everything is perfect. Now we'll give the liner the once over to ensure that's all ok as well.

The cylinder liner has cleaned up perfectly so now we can carry on with the rest of the front end and then move onto the piston etc.

 Here's the next step in the crankshaft manufacturing process. The big end has been turned and we check the fit of the original con rod, which has been cleaned and drilled for lubricating purposes.

Now we machine in the counter balancing and porting.

All finished and the rod ready to refit into the crankcase.

Make a new back plate gasket and fit the back plate.

Now its onto the prop driver and spinner nut.

 

Now that we've got the bottom end all sorted lets take a look at the piston/liner assembly.

(Before)

(After)

Cleaned and drilled rod.

The next item on the list is the new piston and a new gudgeon pin.

 

Piston fitted to the engine, contra fitted to the liner.

Cylinder head on.

Compression screw was cleaned up and reused.

Next up is the N.V.A. and a test run.

Here's the needle valve parts all finished, next is the replica of the original fuel tank.

 

And all assembled........

Now we'll make the acrylic fuel tank as per the original........

 

Now we just need some fuel tubing and fuel...............

 

And lets just check the hot restart....

 

Another vintage engine saved from the rubbish bin.