Piston installation to connecting rod question

[suey1958]

Time to try and get the top end together.  I have an .80 over set of weisco's that have never been run. Cylinders were bored and these pistons were installed years ago by a Yamaha shop, Never started. They look new. Trying to re-install after splitting cases. The pins were only moved enough to remove the pistons so are partly still in the piston. The wrist pins are really tight, no rust and very clean. Is this normal? I can get them to move with a deep well socket and rubber hammer but having to hit it a lot harder than what I would like.
Any suggestions ? 

[pdxjim]

Haha, don't be beating on it with a rod and bearing in there.

There are off the shelf tools available or you can whip something up for a few bucks with some all thread, nuts and washers.

Some are tight and some slide right in with no effort, but keep in mind the pins are hardened steel, and the piston is aluminum so make sure its going in straight before you reef on it. 

[suey1958]

No, Just trying to get the pin to move with the piston in my hand,...At that point I knew it was too tight to try and connect it to the rod.
Does it need to be pressed in? if so I can probably figure something out  with a C clamp or similar.

[Striker1423]

No, Just trying to get the pin to move with the piston in my hand,...At that point I knew it was too tight to try and connect it to the rod.
Does it need to be pressed in? if so I can probably figure something out  with a C clamp or similar.

NO! Do not use a c-clamp! That could potentially dicker the piston up. Actually it probably will with a 95% guarantee.  If you have to, take the pin out the rest of the way and oil it up with 2 stroke oil. It might be stiff, but should install by hand (using a small socket to remove it works best for me... again by hand only). If not, buy a piston pin tool. They are cheap assurance.

Aside from damaging the piston with the clamp, using a hammer on the pin to remove it while its in the bike is not the best idea. It really shouldn't hurt it, but ONLY if it's supported and you use love tappy tap taps. This requires a friend to hold the rod to keep it from moving as little as possible and crossing every digit not doing the work. You can mess the connecting rod bearing up, or bend the rod itself. Both would mean crank work if caught, and if not, a whole motor's worth of work if you try to run it.

Reserve the hammering for a blown up motor at which point if the cranks dickered it won't matter. 

[SUPERTUNE]

Too tight...
Cut a slice in a "2 1/2 long 5/16 bolt, cut the head off, put in your drill with a strip of 320g cloth polishing paper like a flap wheel lubed with WD40 and hone the bore just a little, clean well, then lube with motor oil and try to hand push in, if still tight, keep going and look for shiney high spots, make it's just loose enough to push in by hand a little firm. Doesn't need to be fall through loose! That would be too loose without proper sunnen honing mandrel and special measuring gauges to get to 4-6 tenths (inches) clearance (.0004-.0006)

Also pre-fit the pins into the rods with the bearings in first and make sure the pins are not oversized or tarnished.

Before installing pistons use a .003 feeler gauge in the cylinder with no rings on the piston and make sure you can push it through with the feeler gauge in the bore.. If not, get it measured with a dial bore gauge to make sure you have it honed no less than .0035 thousandths of piston to wall clearance.
These are very old school pistons and at .080 over the skirts are quite thick and need this clearance to jet it properly.
Keep in mind at 2mm oversized pistons will drive up the compression ratio right to the edge of today 93* pump gas!
Set timing no more than 1.9mm BTDC for fixed ignitions.
Chuck

[bitzz]

Heat the piston

[suey1958]

Thanks,.. Chuck figured out my next question before I even asked it regarding checking the bore / piston clearance.