Question about 1976 Yamaha XS 650 C
In our perennial quest for HP and torque, the topic of cam timing seems to be missing from the threads thus far posted. Yet, cam timing can have a significant effect on overall engine performance and the mix between HP and torque. Since the HM has only a single cam per cylinder, there isn’t anything we can due to vary the overlap for any given cam, but there is certainly some range of adjustability on how the overall cam timing is set by cylinder. With the stock cams, the timing specs for both cylinders are as follows at 1 mm valve clearance Intake Opening 15° B.T.D.C. Closing 65° A.B.D.C. Exhaust Opening 62° B.B.D.C. Closing 19° A.T.D.C. (Anyone have the specs of for the DP cams?) Certainly degreeing in the cams to spec is a good starting point, but my real question is how might HP and torque be impacted by advancing or retarding cam timing? There’s lots of information on how to degree a cam and people have been doing so since the old flat-head hot rod days, but information on how changing cam timing in and by itself affects overall performance and/or the mix between HP and torque (perhaps held as closely guarded trade secrets by the cam manufacturers +/or tuners).
Posted on Nov 10, 2008
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Posted on Jan 02, 2017
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