Do I need to replace the piston pin when replacing a connecting rod?

[dinkyguitar]

Hi All,

I'm planning to get another crankshaft and also replace the connecting rod, but use my existing piston since it's in good shape. The cylinder is also in good shape.

The reason I'm replacing the crankshaft is because the splines that hold the primary gear are worn. The crank I intend to buy has a pro x rod and supposed to have about 250 hrs. of run time...but my gut tells me to replace the connecting rod anyway....

The problem is that I don't know if I should replace the piston pin.

Is it OK to have a "new" bearing ride on an existing piston pin?

I was under the impression that new parts should wear together as opposed to mixing new and used parts, especially bearings.

dinky,

[sandblaster]

Considering the cost of a new one I'd replace it... But, that's not to say you can't use it..
Can you post some pics of what your piston looks like from all sides?
Have you mic'd the piston, pin, and cylinder and compared to new specs?

[treedodgingfool]

New bearing, new pin. Also replace crank seals & main bearings if you aren't already.  Why are you not replacing the piston & rings?  If it's been a year since last replaced, replace it (especially if racing, at least twice a year).  It may look fine but pistons are a wear item.  Wouldn't want to have the skirt crack and drop bits into the just replaced crank.  Personally, I wouldn't screw around with a used crank from somebody else's bike unless I could eat out of the airbox. Also, if rebuilding, I would use an OEM connecting rod, aftermarket internals have not impressed me since most is manufactured in China with less then stellar materials & craftsmanship.  Never used any aftermarket internals (except a 300cc piston) and my racebikes have an obscene amount of hours/mileage) on them with no major issues.

[dinkyguitar]

The reason I'm not replacing it is because it still looks good. The piston was replaced at the time the bike was running. The cylinder still has the cross hatching from honing....But I have to admit, the bike sat for 8 years...still it looks good inside. And it didn't seem like it lacked compression. I can use my calipers to measure the piston...it's a std. bore.

I felt the cylinder and there are no scratches that I can feel.

What do you guys think?













If I decided to get a new piston....will I need to hone the cylinder again? Being I can still see the honing marks?

dinky,

[staffylad]

looks sweet as a nut I would give It a hone just for gud measure maybe some new rings 

[Goat]

I would carefully pull the rings and check the end gap. If it's within spec I would put it back together as is. Don't mix the rings up and remember which side faces up. They are wore a certain way and if you flip them over or switch locations they will wear differently and not last as long. Cylinder looks pretty good, and piston looks nice. If it's going to be a racer then I would replace piston and rings and make sure clearances are perfect.

[dinkyguitar]

Thanks....I went ahead and had the cylinder honed...not I just need to get a piston.

dinky,