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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Valve Timing
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<blockquote data-quote="Mikeant" data-source="post: 118572" data-attributes="member: 3800"><p>I have been following this interesting thread. Mine is a 48 Rapide engine in a Wideline frame. Effectively laid up not quite finished in 1977. At the time I bought new cams from the Thresher down at Lymm. Later I head that there was a batch of cams about that were not properly hardened. I got mine tested; they were too soft so they were nitrided and retested so should now be good. I got out the dial gauge and the degree disc and checked with the following results. No 1 Inlet opens 50BTDC max lift 0.319" closes 92ABDC. lift at TDC is 0.083" and at BDC 0.190". No 2 Inlet opens 49BTDC max lift 0.325" closes 85ABDC. lift at TDC is 0.110" and 0.200" at BDC.</p><p>No 1 exhaust opens 76BBDC max lift 0.318" closes 45ATDC has lift 0.174"at BDC and 0.091" at TDC. I could not get the gauge on the valve stem of No 2 exhaust due to the proximity of the frame so put it onto the tappit screw head instead and obtained No 2 exhaust opens 66BBDC max lift 0.292" closes 21ATDC, lift 0.168" at BDC and 0.062" at TDC. I am surmising that if the rocker arm has equal lengths either side of the pivot the lifts should be the same as measured at the valve but the timing should still be correct whichever.</p><p>Now these cams are not standard as the lift is too much. The inlets are about the same and not too far away from the book numbers, No2 exhaust looks to have less lift that No 1 exhaust but that might be down to the rocker arm. Oh and I checked with the valves on full lift to see how much more I could lever things and the results were not a lot so I clearly have some work to do here. I look forward to the experts' opinions.</p></blockquote><p></p>
[QUOTE="Mikeant, post: 118572, member: 3800"] I have been following this interesting thread. Mine is a 48 Rapide engine in a Wideline frame. Effectively laid up not quite finished in 1977. At the time I bought new cams from the Thresher down at Lymm. Later I head that there was a batch of cams about that were not properly hardened. I got mine tested; they were too soft so they were nitrided and retested so should now be good. I got out the dial gauge and the degree disc and checked with the following results. No 1 Inlet opens 50BTDC max lift 0.319" closes 92ABDC. lift at TDC is 0.083" and at BDC 0.190". No 2 Inlet opens 49BTDC max lift 0.325" closes 85ABDC. lift at TDC is 0.110" and 0.200" at BDC. No 1 exhaust opens 76BBDC max lift 0.318" closes 45ATDC has lift 0.174"at BDC and 0.091" at TDC. I could not get the gauge on the valve stem of No 2 exhaust due to the proximity of the frame so put it onto the tappit screw head instead and obtained No 2 exhaust opens 66BBDC max lift 0.292" closes 21ATDC, lift 0.168" at BDC and 0.062" at TDC. I am surmising that if the rocker arm has equal lengths either side of the pivot the lifts should be the same as measured at the valve but the timing should still be correct whichever. Now these cams are not standard as the lift is too much. The inlets are about the same and not too far away from the book numbers, No2 exhaust looks to have less lift that No 1 exhaust but that might be down to the rocker arm. Oh and I checked with the valves on full lift to see how much more I could lever things and the results were not a lot so I clearly have some work to do here. I look forward to the experts' opinions. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Valve Timing
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