wrist pin press

[bitzz]

Something has to locate/center the piston on the pin.
On these Yamahas, as most two strokes; the rod is located by thrust washers on the crank, and the rod "floats" on the pin.
On a four stroke you can locate the rod with a press fit pin and let the big end "float" on the crank.

No one noticed I wrote y'all a poem....

[m in sc]

oddly, my old galaxies 390 (fe design from the 50s) had full floating pins when i rebuilt it.  so its all over the place. My old 351W & other small blocks were press fit, as are the ford I-6's.   

 

[Dvsrd]

if i can't just slide it out, i grab the puller. that tool exists for a reason. that's all i'm saying. 

My reply was only meant for motorcycle 2-stroke engines. On my RD 350's cleaning off that tiny burr/ ridge makes a world of difference. If the wristpin is a push/ sliding fit in a new piston, the only difference when removing the pin from a used piston, are these tiny burrs at the edge of the circlip groove.
OTOH, I haven't removed any car/truck/tractor wrist pins in at least 30 years....

[1976RD400C]

When I worked in a machine shop in the 70's most of the US built car engines had the press in pins. I always thought it was a way of ruling out circlip failure disasters and one less wear spot to cause more slop in the rod to piston fit that could cause noise.

[m in sc]

ive never used that puller on a car engine, just fyi. no reason to since you have the rod off the crank to swap them out.

Im not sure many realize how easy it is to bend a 2-stroke rod to the side, even just a tiny bit.