New Piston

A bit disappointed with my new piston, it looks like it has been water damaged or something. It doesn't seem to be physically compromised, so it went in, after a good clean. The new and old pistons are physically the same - 210 grams

It went in, no problem and the rings were in perfect condition so should be OK. I broke the temperature thermocouple as it was all going back, but one from my FZR stock of parts will fit. Just need to fill up liquids tomorrow and see if it works!

RD 350 Update

Just to make a note of the squish values, measured with the existing pistons (one cracked and the other OK).

Nothing surprising really all around 1.0mm which is appropriate for a 175cc cylinder.

Cleaned the head up and the piston (for measuring the squish), stuck the bits of solder on to the top of the pistons and then tightened down the head and rotated the engine one time to ensure the solder got squished on both sides. The cylinder and head don't look any worse for where, but this is becoming a nasty habit every couple of years, so will have to investigate a little.

Yamaha 350

Just back from hols. in Scotland and back to 30 degrees centigrade in the workshop! The 350 had been getting really difficult to start - only pushing it would work, so I was troubleshooting before the holiday, the left hand carb was missing the idle screw so I thought I had found it, anyway I sourced a new idle screw and it was exactly the same!

So with fuel and a spark, the next thing is compression. I pulled the generator cover to see if the left hand crank seal was blowing, and no oil in there, so I decided to remove the head, once it was off it was clear what the problem was.... The piston was cracked on the crown and all the way down to the gudgeon pin, this is potentially the 3rd time this has happened. Maybe the consequence of over revving....?

I have purchased a Mitaka replacement that I am assured is exactly the same as the cracked one, £60 from PJE motorcycle Engineering posted.