Sidel ST770 rebuild questions

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DiegoVV

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Dear colleagues,

Recently, I´ve received a quite old Seidel ST770 (I think this unit dates back to the 80´s). Last time it was started, Queen band was on the top of all lists.

The owner is a good friend of mine from my RC racing days, and he unsuccessfully tried to restart it last year...and that´s where I came into play.

I´ve started opening it, and while dissassembling the cylinders I notice something quite disturbing: The head of the pistons have an eroded groove (Deeper in some cylinders than in others), indicating some kind of contact in the TDC with the cylinder head. One piston has even a half moon mark indicating a valve-piston contact.
WhatsApp Image 2024-04-15 at 17.42.20 (4).jpeg

WhatsApp Image 2024-04-15 at 17.42.20.jpeg


The instructions are more focused on the operation of the engine than in its adjustment or its design, even the exploded view is quite small with a low resolution image, not enough for our purposes.

Apart from this, the cylinder barrel retention system to the crankcase is different from the one shown on the exploded diagram.

I wonder if I should raise the cylinder barrel with some kind of shim / spacer in order to enlarge the distance from piston to the head in the TDC. If so, the question would be to know how much clearance I should give, that will determine the thickness of the spacer.
WhatsApp Image 2024-04-15 at 17.42.20 (1).jpeg



Thank you very much my friends!!!
 
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