Cylinder reboring

Just grand...The new piston from Wössner. I had been puzzling over this issue for quite a long time: for srx 600 model, there is no problem to get a new piston for reboring - besides the larger OEM size, there is also a Wiseco option. Well, for japanese 400cc, you may get the OEM piston (5Y6-11631-01-A0), on the other hand, that is the standard piston size which is no use - in this case, the whole new cylinder barrel with a smaller boring would be required to get it working. So, here is the deal: since there is no aftermarket variant for srx/xt 400 available, we laid up heads together with Oulehla Motor Parts, the well known machining specialist in Sternberk, Czechia. It turned that the Honda xr 400 dirt bike has the same boring, though a small adjustation of the piston top showed as necessary. It was needed to cut a new spaces for valves identical to OEM part on a milling machine. The new piston comes with the piston pin, ring set and circlips.

A genuine srx piston compared to the lower Wössner

The milled valve spaces in a front-rear direction (srx) as oppose to the diagonally oriented, bigger genuine spaces (xr) 

         

Welded tank

A milestone! The tank was finally welded by a professional welders school into a desired shape.

Prior to to welding, the 0,7 mm metal sheets (the original thickness) were cut and formed while clamped in a plain vice. The former welding method was intended to be brass or silver soldering, in the end it was MAG, if I am not wrong. An industrial-type laser welding which may have lead to a best results was unfortunately out of reach.

Well, due to the small thickness and a high temperature, the sheets depressed around the seams, but the actual form is attained and the tank copies the curve of the frame. Anyway, the finalisation opens a space for working with metallic resin for which I am already looking forward. Subsequently, the frame was wrapped with a protective scotch paper and the tank seated well during the first check.

 The two pieces of fabricated sheets on each side

 welded workpiece below

The round corners will be welded soon as well