Now the cylinderbase nuts can be tightened. As there is no space to use a torque-wrench, it is better to use a short 12 mm ring spanner and tighten all nuts from the same angle with the same hand/arm in order to get possible equal tightening. That is why I also left the intake manifolds off, there is a little bit more space now to "wrench"!

Yamah TZ250J cylinderbolts tightening