S1 Publishing(Oxford)© 1999-06

World of motorcycleS
S1 Publishing(Oxford)© 1999-06
Engine Rebuild
Gilera Runner 125 FX
This is just a general guide.
If you are about to do your own maintenance, using these pages, I take no responsibility if you get things wrong!
Page 1
Now all the parts have been found, and the engine has been thoughrouly cleaned, it's time to rebuild the engine.
 As his water pump as well as the splines on the crank were damaged the complete engine had to be overhauld. 
 The water pump bearings had broken up and four of the ball bearings had disintergrated (along with one of their rubber seals). Somethiung had been ground up into the sump which had caused more damage to the piston and the bore, the piston has been replaced ant the bore "honed". Honeing is juest making the rest of the bore meeet the scratching so that the piston rings  meet flush with the bore.
The other damaged parts which are being replaced are:
1. the engaging pinions for the kick start (both parts)
2. The starter drive gear and fins (in one piece on this model)
3. The casing from the variator (which is being replaced with a polini(.com) race variator).
4. water pump belt drive wheel.
1. Drift the bearings and shaft for the water pump
2. Using circlip plyers and a screwdrive press home the circlip
3. Place the water impeller in postion and tightn, NOTE! it's got a reverse thread!
Replace the crank into the right hand side crankcase, (use a drift if neccessary) make sure that the crank is in streight.
5 Smear a small amount of gasket compund in the edges of the crancase. Ind replace the two dowels.
6 Then replace the crank and otherside of the crankcase into position, and gently using a wooden block (rotate the postion of the block to keep the casing as streight as possable) and a lump hammer tap the crankcase  together
7. Replace the crankcase bolts and torque them correctly (12-13 Nm in this case) spin the crank and see if it runs  freely ( make sure the con rods do not bang on the casings too much when doin this.)
8. Replace the piston into the con rod making sure that you don't lose the circlips into the crankcase. Double check that both sides if the piston have circlips, falier to do so will cause the gudgeon pin (wrist pin) slide out of position and leave a bad groove in the barrel, or worse.
Small end bearing goes in first
Then the gudgeon pin fits through the piston and the bearing
last the circlip fit into the groove in the piston where the gudgeon pin fits.
Click here for Page 2
Updated for 2009
Version 3 24-01-2017
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