JKCanuck

It's important to remember that forged pistons are heavier, have different expansion characteristics and are usually preferred for high performance apps, for their greater strength. You may notice more vibrations due to the weight, and you should plan for a longer break-in because of the different forging densities that cause somewhat uneven expansion.

I'm old (81+) with a new acquisition of a 1977 Canadian market TY175. I'm way past stand-up motorcycling leg strength, and, so, seeing this bike advertised for a song, I remembered back in the day, Cycle World in the States reviewing the then new TY175 and remarking that it was the best "trail" bike they'd tested. I bought it, thinking it was so light and maneuverable, that it would suit the woods and logging road riding available here on Vancouver Island. I found right away that the foot pegs are too high and far back for my wretched legs to be comfortable in my preferred sitting style, so I acquired foot peg brackets and rear brake pedal from a 1975 DT175. This moved the pegs down 2" and forward 3.5". Some trialers have criticized the splined stubs on the frame as hanging up on rocks, but I thank Yamaha for their thoughtful inclusion. Seems like they anticipated that trail bike use. I also added a little extra padding and a new leather seat cover fashioned from an old leather jacket. After struggling with the weight of a couple of Honda TL250s over the years, it's a pleasure to man-handle only 80-odd kilos in my dotage. Anybody else "mis-using" old trials bikes?