MOPED ARMY

I like your drawing.. and your pusher/puller.

I made a similar one years ago.

First check for a burr that is binding the fit.

And you are using some 2 stroke oil for lube?

If it still won't got... then >>

You could ease this situation by very carefully sanding the wrist pin bore (in the piston) with some 500 or 600 grit wet and dry sandpaper wrapped around a wooden dowel (or metal tubing).. you can slit the rod with a hacksaw to slip the paper into the slit.

I would use paper that is already partly worn out...and wet it first... then put the piston between your legs and scroll the rod or tube between your hands like you are trying to start a fire.

Do this very sparingly... then rinse the piston and try the fit with the pin.. sand lightly... try it... sand it.. try it..etc.

When you get it to slide in... then clean the parts very well... and assemble it with lube.

Don't go too far.. you still want a firm fit.

Thanks a lot Fred, I'll give that a try. Do you know why Motobecane would make it such a tight fit ? I don't understand why they would do this. I'll shoot for a firm fit but still be able to push it in with my fingers. Thanks.

Moby,

As Jim says, heating the piston is essential if the pin is tight, you can also freeze the pin.

If you follow Jim's advice without a helper, the pin should never get tight in the rod end bearing, just test for play as you press the pin in place.

Ron

I

Ron:

You are correct about modifying clearances set up by the factory. Although my experience with a Kinetic crankshaft implies otherwise.

And Also:

When installing the piston pin clips/snaprings/keepers/ whatever they are called, put the flat side out out if it's a snap ring. Look at a large washer and note how it has a flat side. This is the result of it being a stamping. Snap rings are made the same way and the flat side out prevents the risk of it popping out.

And Also Also:

The open end of a snap ring should be placed at either 12:00 o'clock or 6:00 o'clock relative to piston travel. Honda found that in racing the piston stretches and the snap ring can pop out at the other positions.

Jim C.

Actually ... It is not the piston "stretching" at all...

You put the open end of the C shape either up or down to prevent the high "G" forces at TDC and BDC from springing the C shape closed.

Hi! Could it be the wrong piston or a bad new part? Sometimes you get something,especially foreign made like in India that is enough out of tolerance to ruin your fit.I wouldn't force it,I'd try another piston,I think. Hope you have success! You know,more and more `knock-off' parts are being imported. Fuel valves are a good example of shoddy workmanship or inferior materials being sold as replacements for good bikes like puch, tomos,etc.