So things are getting weird.
For clarity, other than popping out of gear which is the reason for the tear down, my it250 runs super crisp. Gobs of power. Compression is spot on.
After taking the cylinder off, the piston looks perfect. Zero scoring on piston or cylinder. Rings also look perfect. So I didn’t plan on doing the piston which is a happy surprise.
However, here’s where things get weird. WTF… the connecting rod is bent. Slight bend to the left. How the F did this happen and why does the bike run great?
The only conclusion I came to is that before I bought the bike I assumed the previous owner seized the motor in a gnarly way, hence the slight rod bend, which is still impressive to bend a rod. So I assumed I’d now be at the 2nd or 3rd oversized piston.
Extra weird: nope. I’m at the stock size piston and cylinder. How the F did the rod bend?
Is it possible the dude replaced the entire cylinder and piston with a STD size? That seems unnecessary.
Is it possible when I submerged the IT in water in the pines, it got water locked for a second and that created the slight bend? I doubt it since I turned the bike off right away and pulled plug to drain water before starting it. Nothing makes sense.
So that’ll be another $150 to replace the crank and rod. Shit.
6 responses to “IT250 conundrum”
Published - Aug 17, 2010
This is Dave kings Shaft driven 1978 Yamaha 750 triple XS. In between moving from Philly to the Lehigh Valley to be closer to his beloved trails, it took Dave about a year to get the bike to where it is now. It was pretty stock when he first bought it. On a side note […]