Rephasing, What is it?

plane_ben

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This subject keeps popping up in my reading about the venerable XS650. What is it? I know the crank rotates both pistons up and down together, and fire alternately. So is rephasing a change in the crankshaft and camshaft? If so, why? What is the advantage.
 

inxs

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- this is a tic of mine - i love rephased motors...yes this is changing the crank set up so the pistons dont travel together...the advantage is that you dont lose energy when both pistons are at TDC as 1 piston is always mid stroke when the other is TDC..ie rephase-when one piston is not moving (TDC) the other is at max velocity (mid stroke)...removes the search for energy to overcome inertia when both pistons are stopped together (non-rephased TDC)
- so there is a power saving
- this leads also to less vibration as the motor runs smoother
- better responsiveness
- slightly torquier
- if you do this weld the pins to the flywheels...balancing helps too

- there are 2 ways of doing this

- split the crank in the middle-rotate the right hand side 3 splines and press back together...277 rephase
- split the crank, replace the 2nd flywheel from the right with a slightly modified 3rd flywheel (remove 21mm from the pin boss where the cam sprocket seats), use a 270° pin and press together 90° out of phase...270 rephase

- both of these processes require a suitably modified camshaft and a cam-driven ignition system...a good time to consider installing a permanant magnet alternator and dual lobe points cam

- in my opinion yamaha missed a golden opportunity to produce a truly extraordinary motor by turning this idea down...i have done this and highly recommend this to anyone interested in spending the effort...virtually all modern-day parallel twins are built this way

xsstandard.gif
xsrehase.gif
 
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inxs

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- sure...you can get pins and cams from heiden engineering in holland - they are service partners with mikesxs so you may be able to get them there too (although im down on mikesxs and wont deal with them)...or Daryl Hutcheon in Melbourne Australia - i know bertauts also supply (or more to the point source) them but strange things are happening there at the moment so i wouldnt touch them until im sure whats happening...

- Heiden...http://www.xs650.biz/ -not on their site-u need to ask for these
- Daryl Hutcheon...promctun@bigpond.net.au ph: aus 03-9330-4909

newpins.jpg


- the pins...if you look closely you can see the offset between the left and right hand splines

crank.jpg


- schematic for the crank mid-section
 

pyrocentric

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It should be noted that this requires at least a 20 ton press. That and the cost are the only reasons I'm not doing it on my current rebuild.
 

eric123

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If one does all the work themselves the cost to re-phase isn't too bad...It's the price of that damn camshaft that pisses me off...
 

650Skull

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Pamcopete was designing one in conjunction with MikesXS who was making a rephased cam for the XS, Go to Pamcopete's site Here or contact him through XS650.com as he is a member and should be able to help you out
 

650Skull

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277 is minimal cost, 270 is VERY expensive. Theoretically the 270 should be but for the cost verses vibration :shrug: A friend has just done the 277 and he is getting some vibration over 60mph but not enough to see through the mirrors
 

xsjohn

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Skull......that's a good question.......I still miss my silver Kawasaki Z1R.......but the speed limit was 55 then and I got in too much trouble..........:doh:

Secondly.....wish all this global warming would go away so it would warm up and I could go riding...........:laugh:

xsjohn
 
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Jack

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