Scrambler on the basis of Yamaha YBR 125. Part 1: EGR removal and carburetor cleaning

The first thing I wanted to do after buying the donor was to remove the EGR system and clean and tune the carburetor so I wouldn't have to revisit these issues later.

EGR is a gas recirculation system that was installed on the YBR assembled for the European market. It is a small block with a couple of rubber tubes. By and large, for such a small cubature it is either there or not: it does not affect the engine performance, but nevertheless, it was decided to remove the block and plug all the associated holes in order to

(a) Reduce the volume of the system, thus speeding up its warm-up at start-up

(b) Reduce the overall weight of the motorcycle

(c) To make room for a new fuel tank layout

Removed this unit, plugged with bolts the spigot on the air filter and the spigot on the manifold and for the cylinder head turned out a plug from steel about 2 mm thick + aluminum gasket under it, tightened it all with standard bolts:

Let's move on to the carburetor. Mikuni VM-22 is an excellent, vigorous - as much as you cranked it, so it goes! And to make it drive even better, I started its global cleaning. In brief: I removed the float chamber, adjusted the float (along the casting line), unscrewed all the jets, blew out with a compressor and a special cleaner, also flushed the needle valve and a rather interesting vacuum valve on the side under the round cover with a rubber membrane (by the way, can someone tell me why it is there?). Here are some photos:

Before installation I turned the quality screw to 2 and a bit turns and oh miracle - the engine started at the first attempt! I played with the screws a little more and achieved stable operation of the engine in different modes.