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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Omega Pistons - Clearance at the bottom of the skirt
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<blockquote data-quote="timetraveller" data-source="post: 19431" data-attributes="member: 456"><p><span style="font-family: 'Times New Roman'"><span style="font-size: 12px">Assuming that you have just bought the pistons and not had them on the shelf for years why not ask the person you purchased them from? Assuming that they are for road, and not racing, use then a figure typically given for the low expansion pistons is three and a half thou! Several local people have used this and some have had problems. However, what is often not realised is that with this very low clearance it is vital that the bore of the cylinder is exactly perpendicular to the base of the muff. Roy Robertson set up a jig to measure this and typically the base runs out by about five thou. There goes your clearance and here comes the seizure. If this angle only meant that the cylinder was tilted for and aft then it would not be a problem but if it is side to side you will see that there are going to be problems. People who have ensured that the base of the muff is at 90 degrees to the axis have not had problems with their bikes and if the low clearance pistons are fitted at the same time as sealed lower valve guides many of them have found no need to top up the oil between oil changes. Good luck</span></span></p></blockquote><p></p>
[QUOTE="timetraveller, post: 19431, member: 456"] [FONT=Times New Roman][SIZE=3]Assuming that you have just bought the pistons and not had them on the shelf for years why not ask the person you purchased them from? Assuming that they are for road, and not racing, use then a figure typically given for the low expansion pistons is three and a half thou! Several local people have used this and some have had problems. However, what is often not realised is that with this very low clearance it is vital that the bore of the cylinder is exactly perpendicular to the base of the muff. Roy Robertson set up a jig to measure this and typically the base runs out by about five thou. There goes your clearance and here comes the seizure. If this angle only meant that the cylinder was tilted for and aft then it would not be a problem but if it is side to side you will see that there are going to be problems. People who have ensured that the base of the muff is at 90 degrees to the axis have not had problems with their bikes and if the low clearance pistons are fitted at the same time as sealed lower valve guides many of them have found no need to top up the oil between oil changes. Good luck[/SIZE][/FONT] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Omega Pistons - Clearance at the bottom of the skirt
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