Before we continue with 100cc engine restoration , I would like to briefly share with you some karting photographs that were given to me recently. It was not the technical content of the photographs that impressed me but the sense of fun and friendship that they depict. How many modern day karters will have photographs like these to look back on in forty years time? If any of you older karters can identify the kart or any of the karters shown, I am offering the prize of a drive in an historic kart at one of the upcoming 50th anniversary events. The only clue I will give you is that they are all west country drivers, the date is 1960 and the circuit is Crisbett Mendip. Answers to the address at the foot of the page please and best of luck. 100cc Engine Restoration (Part 2) Having established that your barrel still has some bore life left in it and that you are going to bite the bullet and restore your cherished engine, proceed as follows.
Carefully remove the barrel while supporting the piston and connecting rod with your other hand. Put the barrel to one side for now, we will need to measure it up at a later date. Next, remove the piston circlips and slide out the gudgeon pin, having packed the mouth of the crankcase with rag to avoid any loose rollers falling into the engine. Note the arrangement of any small end spacers that may be fitted. Have a quick look at the small end eye in the connecting rod. Any signs of scoring or bluing will mean that a replacement rod is probably going to be required. Some of the very early connecting rods have a plain bush fitted to the small end eye. Again, inspect for damage or excessive wear.
Check that the piston rings are not trapped in their grooves and that the ring pegs are still in position. Most early pistons will be of the boost port type and will have a rectangular window cut in the side of the piston. Check carefully for cracks in the piston skirt, especially around the boost port window and the transfer passage cut-outs. Depending on the state of tune of your engine, you may have additional holes drilled in the piston that connect to additional transfer ports. Five or seven port arrangements were not uncommon. Some later engines will be of the TT type and may not have the window in the piston. Carefully remove the barrel base gasket or gaskets without tearing them. You will probably have to make new gaskets using the old ones as templates so take care. That’s the top end of the engine removed, now for the bottom end. Before you can proceed too far with dismantling the bottom end of the engine you are going to need one or two basic but essential tools.
The first of these is a sprocket puller, still available from most good kart shops. This will enable you to remove the engine sprocket when used in conjunction with a home made chain wrench. The chain wrench can be made from an old chain and will enable you to lock the drive sprocket prior to undoing the crankshaft nut. The next tools you will require are an ignition locking tool and an ignition extractor. Again, the locking tool can be manufactured at home and is used to lock the ignition rotor to allow the crankshaft nut to be undone. The extractor can then be used to remove the rotor from its taper on the crankshaft. If you have Motoplat ignition, the tools are still available from good kart shops. Should you have the original CEV flywheel magneto ignition you will require an extractor with a different thread form on it. These extractors are no longer commonly available but I can probably source one for you if you want to persevere with the original CEV ignition. That’s all for this month, next month we will separate the crankcase and inspect the parts removed from the engine. Jon Pearce Helpline: 01380 730585 (Evenings only) Competition Address: J. Pearce, 4 Gaisford Chase, Worton, Devizes, Wiltshire SN10 5RX.