Saito V4PR repaired

The first time I saw a Saito V4PR it was love at first sight - these masterpieces of steam engineering have not been made now for about 40 years. I recently purchased a broken Saito V4PR from the website we all love, it was correctly advertised as spares and repairs. From the photos I had a good idea what was wrong so bought it. The fitting screw (M2 x 11) that holds the piston valve drive rods to the drive wheel had sheared off flush with the drive wheel (clear from the photos as advertised). The reason for this was the piston valve for one side of the engine was seized solid in the cylinder head - then probably, someone, when attempting to rotate the engine forced things and the bolt sheared. [Vous devez être inscrit et connecté pour voir ce lien] The Saito V4PR engine is a V Four Single acting engine of 2.5cc, so each cylinder has a capacity of 0.6125cc, which is tiny. It has a bore of 9mm and a stroke of 10mm. It's a piston valve engine that will rev to 6000 rpm, but produces maximum power at 3200rpm and it weights 380 grams. Knowing the Piston Valve was seized solid in the Valve Sleeve, the whole assembly was removed from the cylinder head and the complete assembly left to soak overnight in WD40. Despite this the piston valve remained stuck fast, so a thin rod was passed through the Valve Sleeve into the inside of the Piston Valve, the rod was then used as a punch to gently persuade the piston valve from the sleeve. Once out the Piston Valve was checked over, no scores or grooves were found, just some staining. [Vous devez être inscrit et connecté pour voir ce lien] The piston valve was polished to remove the staining with Brasso, then washed thoroughly, before being coated in steam oil. The Valve Sleeve and O rings were also liberally coated in steam oil. The Piston Valve was then inserted into the Piston Sleeve. The Piston Sleeve is a clever piece of design, since this is how the steam is diverted for forwards or reverse. The engine looked like it hadn't been run and the O Rings on the Piston Sleeve showed no signs of wear, so apart from making sure they were covered with a generous coating of steam oil, I left them in place. The cylinder head was then lubricated again with steam oil and the piston sleeve slid back into the cylinder head. Reassembly was straight forward, albeit it fiddly with such tiny components. The stainless steel Reversing Lever rod was screwed into the Valve Sleeve, this retains the sleeve in the head and the two reversing rod were then linked. The piston valve drive rod assembly was then reconnected. Having done one side of the engine, I then disassembled, checked and lubricated the second side. [Vous devez être inscrit et connecté pour voir ce lien]
When replacing the sump care has to be taken to make sure the flats on main bearings are facing the sump else the sump won't seat properly. Here is a link to a video of the first test run on air

Hello,
Well done ! Good job from an expert, it's nice to see that little engine running again. A good lesson of engineering.

Excellent travel !
Ces petits Saïto ou copies de ... sont des mécaniques précises et demandent un savoir faire et une attention particulière pour les remettre en état.
Beau travail , mon ami !
Ca s'arrose !

Thank you for your support and kind words, repairing these engines and returning them to work brings me great pleasure. I have learned so much from yourselves, reading your posts and seeing your photos, that its nice to be able to contribute to the group and increase our common pool of knowledge.