Cathal said:
ok i don't understand how you center the crankshaft, I have a gilera 172, so different bearings but don't matter, How do ya center the crank? Lets say i have new bearing on and crank is in position it's connected to both cases and in position, Then what do ya do?
Cathal
I've already write it down the crankshaft installing somwhere, but I insert it again,
the exact values is for the Piaggio 50 cc engine with original type bearings!
Remove the crankshaft from the Piaggio crankcase, first you remove all of the parts from the two axle I don't detail it (flywheel, variator) then you remove the crankcase screws, after that you heat the each side of the crankcase where the bearing is with a heating gun. Then you use a crankcase puller (at the heated side) or an universal puller with home made adapters, but never stretch the crankcase everywhere even the surface where the two half touch each other. so when you push out the crank from the each side then, you can do it the same method at the other side. Removing the bearings from the crankshaft needs a special two arm bearing puller (or two very soft wedges).
Now I don't detail the cleaning and other things, so the reassembling: There are two way: 1. if you put the bearings onto the crankshaft first, or 2. when you put the bearings into the cases first. The first is the easiest, and the second is the reccommended by the manufactures.
All of the two method maybee very similar. I write the 1. method. So you can heat the bearings with heating gun (and not with fire!!) you can put the crankshaft to the freezing if you want more easier job. So you can put the 2 bearings to it's end place. Then you cool down the crankshaft and heating the each halfcase, so you can put the crank to the halfcase, then you put the positioning washers and put the Loctite to the sealing surface, then you can make this on the other halfcase. After that you can assembly it, but even if the crankshaft falls into it's place maybe it can be tense. So you need a crankshaft assembly tool (this tool pull, the crankshaft to it's place -> a very simple tool, like a very thich iron sheet with holes). then you can tighten the crankcase srews crosswise (don’t use the original crankcase srews for the pulling together). You can test the rotating before you put the oil seals in their place. If it rotates very easy you can check it's axial play: this is 0,10-0,12 mm if the crankcase is hot and this value must be 0,06-0,08 if it’s cold, if it’s less than 0,02-0,03 you can split it and reassembly again!