ES2 Engine specification needs

Previously paul_abbott wrote:

Is there a source for engine clearance specifications for a 1936 ES2? I am fitting a new piston & rings, and need to hone the cylinder to remove a bit of surface rust. I cannot find a spec for piston to cylinder clearance in any manuals or literature I have. I also need the Valve seat angle and valve face angle specs to properly seat in the valves. Also would like the gudgeon pin to rod clearance specification. I have a manual which lists ring slot gap as: 0.025" to 0.030" for top rings and 0.008" for the scraper ring. Is this correct? Thanks in advance for any help! Cheers! Paul Abbott. Incedently my engine is a 1936 ES2

Previously richard_cornish wrote:

Hi Paul,

Honing the cylinder will probably be a bit more than cleaning off the surface rust as if the engine has done many miles there is usually a significant wear ridge at the top of the bore where the ring travel ends. This is not a parallel wear up the length of the stroke but is more excessive at the TDC tipping point of the piston which forces the top ring against the front and rear of of the cylinder as the piston changes direction. There may also be wear on one side the cylinder if there is any mis-alignment of the con rod or cylinder to crankcase mating. You don't say what make your new piston is but if it is an original type ( Hepolite etc. ) you should have at least 7 to 8 thou. but if you hone your used barrel it will probably be about 10 or more.I have run them up to 15 thou for racing. The measurement should be taken with the piston half way down it's travel at either thefront or back thrust face and the bottom of the skirt. A set of feeler gauges is as good as any to measure it with. The small end should have at least 0.002" clearance and you should be able to feel a movement when you put the gudgeon pin in. This is to accommodate the heat transfer fom the piston and you will often see that the bush has turned in the con rod when the pin is too tight. The valve seat angle is 45 degrees and so is the valve head. The method of having slightly different angles to give a smaller seating is a relatively modern production techique which is cheap and easy to produce. The valve headsshould be blended to the seating ring with the outer diameter reduced to slightly larger than the seating area with no sharp edges. This can bedone in an ordinary drill stand with emery cloth.It will be best if you can avoid cutting or grinding the valve seats as lead free petrol is not kind to the standard cast iron but in use the seats become work and heat hardened so if you cut them it exposes the softer fresh metal. Try using an old valve to grind the seat before grinding in your good ones.The ring gaps look right and the second ring should be about 0.015".The top ring gap looks excessive but this isto allow for the flame front causing rapid expansion. Although it is not specifically for Nortons, Phil Irving's Tuning for Speed is a good reference to get.

Hope this is of some use, Richard.

Previously paul_abbott wrote:

Is there a source for engine clearance specifications for a 1936 ES2? I am fitting a new piston & rings, and need to hone the cylinder to remove a bit of surface rust. I cannot find a spec for piston to cylinder clearance in any manuals or literature I have. I also need the Valve seat angle and valve face angle specs to properly seat in the valves. Also would like the gudgeon pin to rod clearance specification. I have a manual which lists ring slot gap as: 0.025" to 0.030" for top rings and 0.008" for the scraper ring. Is this correct? Thanks in advance for any help! Cheers! Paul Abbott. Incedently my engine is a 1936 ES2