XS650 Yamaha Rephased 277° Stock Crankshaft
This is a low mileage 1980 model 447 stock XS 650 crankshaft I rephased at 277° with original parts.
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XS650 Crankshaft Specifications below:
The cam chain crank drive sprocket is pressed on tight so I moved the notch in the adjoining cheek. (shown above) You can press the cam chain sprocket off and press it back on aligned with the crank cheek. This is for a 277° crank rephase.
Megacycle 277° camshaft updates here: http://www.650motorcycles.com/270277updates.html
Fitting an early model compression release here: http://www.650motorcycles.com/CompRelease.html
277° Ignition System Modifications: Click Here!
I drilled and tapped another 4mm hole to mount a second stock timing mark plate. Now there are two actual TDC marks on the rotor, and marks on the stator gold tabs for 15°, 40°, and 45° for each cylinder. The aluminum piece of 1/2" by 1" bar stock lever under the loose case stud nut is where I seperate the crankcase halves, it is in the above image to show the location.
Wiseco 81mm 763cc piston kit with oversize sleeves installed above. Watch the movie of the number 1 cylinder at Top Dead Center and the number 2 cylinder moving at maximum velocity while I turn the crankshaft back and forth by hand at the link: ** Click Here! **
Basically, with a 277° crank design twin cylinder engine when the number one piston is at zero velocity at top dead center, piston number two is at or near its maximum velocity. Rod length and crankshaft stroke can vary this exact 90° point but that length is insignificant compared to the more effective rotational momentum impulse changes that are actually turning the crankshaft. This makes the engine crankshaft impulse delivery smoother compared to a standard 360° crankshaft twin where both pistons are at TDC and BDC together, even though they are on equally spaced "rocking couple" power strokes. Additionally, the exhaust sound also changes from two equally spaced notes, into two close pulses like that of an Italian Ducati motorcycle for example.
XS650 Special Long Connecting Rod Info: Click Here!
XS650 Cycle Links, Images & Info: Click Here!
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