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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Leak down test
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<blockquote data-quote="Monkeypants" data-source="post: 125293" data-attributes="member: 2708"><p>My OZ Rapide was down around that percentage, however it all seemed to be leaking through the valves, according to the leakdown test. There was a loud hiss from both the carb and the exhaust on the rear cylinder. The front cylinder was marginally better but also showed leakge thru the valves.</p><p>So I knew beforehand that the problem should be with the valves and the cylinders most likely could stay on.</p><p>It turned out that the problem was due to carbon specs on all of the valve seats, worse on the intakes and the very worst on the rear intake.</p><p>Cleaning that off and lapping the valves to gas tight brought compression right back to the "excellent" area on the gauge, both cylinders.</p><p>When the compression dropped off I assumed that the rings and bores were worn and was about to order everything for a complete top end redo. After the leakdown test indication that idea was put on hold.</p><p>The carbon buildup was due to worn-out needle jets causing a very rich mixture.</p><p></p><p>Looking at the carbon deposits on Bill's 1200, this could easily be causing the compression loss there.</p><p></p><p></p><p>Glen</p></blockquote><p></p>
[QUOTE="Monkeypants, post: 125293, member: 2708"] My OZ Rapide was down around that percentage, however it all seemed to be leaking through the valves, according to the leakdown test. There was a loud hiss from both the carb and the exhaust on the rear cylinder. The front cylinder was marginally better but also showed leakge thru the valves. So I knew beforehand that the problem should be with the valves and the cylinders most likely could stay on. It turned out that the problem was due to carbon specs on all of the valve seats, worse on the intakes and the very worst on the rear intake. Cleaning that off and lapping the valves to gas tight brought compression right back to the "excellent" area on the gauge, both cylinders. When the compression dropped off I assumed that the rings and bores were worn and was about to order everything for a complete top end redo. After the leakdown test indication that idea was put on hold. The carbon buildup was due to worn-out needle jets causing a very rich mixture. Looking at the carbon deposits on Bill's 1200, this could easily be causing the compression loss there. Glen [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Leak down test
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