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Crank build for racing engine
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<blockquote data-quote="davidd" data-source="post: 179170" data-attributes="member: 1177"><p>Hats off to Greg for pushing the limits with no secrets. I went to the effort of publishing a book about my racing experience, so there are no secrets here. I built the engine in David Tompkin's Racer in 2018, and its only maintenance has been installing a new piston a few times. The bikes usually do about a hundred racing miles at the smaller tracks per weekend, including one day of practice. At the longer tracks, that will double or triple based on the need for practice.</p><p></p><p>I began ordering Carrillo rods with some extra clearance in the small end about 20 years ago. I did the opposite of Greg's by lowering the rings to get them away from the piston's exhaust pocket, which showed signs of melting. This was a mod that Carleton Palmer did on the original JE pistons. The compression ratio on petrol is 11.23:1, but the Mk2 cam knocks that down to 10:1 dynamic CR when running. There is scuffing on the piston, but to date, there seems to be no reduction in reliability. Dave did not change the piston this year. </p><p></p><p>The wrist pin does show bluing, but it has not been a problem. The heavy valves show no problems and rev happily to 7000 year after year. The Mk2 will only make about 39 plus HP at the wheel, but it seems to do it reliably for long periods. I think the reliability has been a boon to a rider new to racing, as most of us are. A professional racer would probably be bored. But the bike is a joy to ride. Dave won three of his first four races this year, and his average speed at Roebling Road was 82 mph. Not bad for a Comet!</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 179170, member: 1177"] Hats off to Greg for pushing the limits with no secrets. I went to the effort of publishing a book about my racing experience, so there are no secrets here. I built the engine in David Tompkin's Racer in 2018, and its only maintenance has been installing a new piston a few times. The bikes usually do about a hundred racing miles at the smaller tracks per weekend, including one day of practice. At the longer tracks, that will double or triple based on the need for practice. I began ordering Carrillo rods with some extra clearance in the small end about 20 years ago. I did the opposite of Greg's by lowering the rings to get them away from the piston's exhaust pocket, which showed signs of melting. This was a mod that Carleton Palmer did on the original JE pistons. The compression ratio on petrol is 11.23:1, but the Mk2 cam knocks that down to 10:1 dynamic CR when running. There is scuffing on the piston, but to date, there seems to be no reduction in reliability. Dave did not change the piston this year. The wrist pin does show bluing, but it has not been a problem. The heavy valves show no problems and rev happily to 7000 year after year. The Mk2 will only make about 39 plus HP at the wheel, but it seems to do it reliably for long periods. I think the reliability has been a boon to a rider new to racing, as most of us are. A professional racer would probably be bored. But the bike is a joy to ride. Dave won three of his first four races this year, and his average speed at Roebling Road was 82 mph. Not bad for a Comet! David [/QUOTE]
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Crank build for racing engine
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