All the cases were soda blasted & vapour blasted to clean and restore them to look as if they just came out of the sand cast moulds. Chris from CC's did a great job and I highly recommend, his website is: http://carbcleaning.com/

The gearbox looked to be in very good or...

Apologies if you were following this blog ! It has been far too long since I have posted any progress on the YD-A restoration.  Since the last post, there has been slow but steady progress, The forks tubes that were completely rusted out have been remade, the fuel tank...

Upon closer inspection of the crankshaft removed from the engine, it was found that the crankshaft is the correct long stroke 54mm component, identifying the engine as a YD-A, the same as my bike's frame. 

When we consider the facts such as:-  

1) my...

A dummy front end was fitted as well as a YD1 fuel tank. The machine is now going away to have it's proper fuel tank made as well as its distinctive dolphin type fairing. 

It's original pattern gear lever has been drawn and scaled from photo's and a cardboard template w...

With a bit of help from Chip Hellie in the US (who supplied me with the drawings) and Guy Pearson at Exactweld who did the excellent welding, I finally got the correct engine mounts refitted to the frame, allowing the original engine crankcases to be reunited with the...

Here I have compared a standard 1957 YD1 production bike crank and conrod to that of a the YD Racer. It is quite clear that the 2 model were totally different, with the YD1 obviously manufactured for production, whereas the YD Racer was all hand finished, with high qua...

The crankcases of the Factory Racing YD-A / YD-B and the production bike YD1 are completely different, when compared side by side.  Sure there are some superficial similarities, but the YD racers were certainly not just modified YD1 engines !!

...

Both pistons showed catastrophic failure modes ! The top piston ring locating pins on both pistons had become loose and made there escape via the piston crown... and the right hand piston had also broken it's bottom piston ring, although luckily not damaging the bore.

T...

Upon stripping I found a small "O" or circle painted on the inner crankcases behind the sprocket. I have no way to be sure, but this mark may have matched the "O" or circle seen on the outer clutch cover, as clearly visible on Osamu Masuko's YD-A at Asama. 

O...