Rephasing, What is it?

[plane_ben]

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]

- 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

[crash]

thanks for the great info.

[shreveport1]

Here's a vid off a rephased xs650 running....sounds Awesome!!


http://www.youtube.com/watch?v=tVpZ7hMXCj0

[plane_ben]

Thanks for the explaination. Sounds like something I will try if my current engine craps out.

[Travis]

Great info inxs! Are there any companies selling kits to do this?

[inxs]

- 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



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



- schematic for the crank mid-section

[pyrocentric]

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]

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]

Here is a link to the 650club of Australia tech section and has all the info on 270 and 277 rephasing http://www.xs650.org.au/tech.html don't forget to read tech no 5

[dsmflattrack]

Flat track racing a 750. Does anyone make an electronic ignition for a rephased motor?.

[inxs]

- have a look here

[650Skull]

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

[BigJimmyW13]

So which is a better set up? 270 or 277?

[650Skull]

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

[xsjohn]

My mirrors are dead clear at 60.........even 70 for that matter and it cost me nothing.....

xsjohn

[BigJimmyW13]

I would assume the 277 is less vibration than the stock set up though right?

[650Skull]

Maybe some have more money than sense, come to think of it why get an XS at all what did i say

[xsjohn]

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..........

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

xsjohn

[Jack]

Originally Posted by bigjimmyw13

I would assume the 277 is less vibration than the stock set up though right?

Depends on the balance factor,stroke and rod ratio. The closer to the balance factor of 50 to 53% the smoother the motor will run. Go to Britbike.com and browse through the BSA and Triumph boards for rephased projects,threre's some very sharp members who have gone the 270 and 277 route.
http://www.britbike.com/forums/ubbth...693#Post212693