TDR250 big end check & new piston install Ep.1

Finally its time to make a start rebuilding the 'top end' of the Yamaha TDR250's engine. Due to a previous Power-valve to piston contact causing immediate engine seizure I performed a complete top end strip down to see what had gone wrong...

After a full inspection and many, many hours or research we (Ben an myself) decided the best course of action was to re-bore both barrels to 2.0mm oversize (larger than Yamaha's maximum of 1.5mm) and source aftermarket pistons, rings, little end bearings & new Yamaha power-valves, bushes, seals etc...

So, given the number of process involved in completing this task as per the Yamaha workshop manual I decided to make this a series of 'short' (or not so short as it turns out!) videos covering the stages of the rebuild.

In this first Episode we start off with running through a few of the Yamaha part numbers relating to the build, checking the big end bearings, then checking the new piston rings for ring gap in the newly rebored cylinders - included is the specification covering this too.

Next I show you how to correctly fit the new piston rings & include a few tips on fitment too especially fitting those difficult gudgeon pin circlips that often ping out and fly across the workshop!

Finally, I cover how to fit the 'built-up' pistons to the con rods together with the little needle roller bearings.

The next video in this series covers the YPVS power valve replacement on both cylinders using all new parts - that's video #1147.

If you have any questions or comments then please add them below & I'll get back to you just as soon as I can.

Cheers for now...

Andy Mechanic!