rephase?

Audy · Posted: July 25, 2009, 10:17 pm Post subject: rephase?

What is a rephased engine. Or what does it mean

schtipp · Posted: July 25, 2009, 10:26 pm Post subject: Re: rephase?

it has to do with the way the pistons relate to one another in time. stock set up for this bike has both pistons rising and falling together.one is compresing while one is exhausting. good because the power strokes are 180 degrees out, bad because the motor is not dynamically balanced. in other words, when its moving the weight is being thrown up and down and makes for excess vibration. makes for its share of loose bolts. leaky gaskets. a rephase is when you change the way the pistons relate by making changes to the crank. so that when one is going down it's helping to push the other up, rather than relying on momentum

Audy · Posted: July 25, 2009, 10:37 pm Post subject: Re: rephase?

Ahh so one piston is up and the other is down? Whst does doing that run in price and is there a power advantage ?

pumps · Posted: July 25, 2009, 11:31 pm Post subject: Re: rephase?

www.youtube.com/watch?v=uHp8k4NG3Sk

Well it ain't cheap.
www.650motorcycles.com...gines.html

650skull · Support Staff Joined: Jul 19, 2007 Posts: 1186

This will explain it a bit better Web Page Name

This is how they do a 270 rephrase Web Page Name

Some more explanations Web Page Name

Now the 277 is a lot easier and not all that expensive, best to wait till you need to replace the crank bearings. When the crank is to be put together again it is twisted 3 splines then pressed on, Gives it 277 instead of 270.
The cam has to be replaced with a rephased one (MikesXS is getting some soon) and the ignition also. (pamcopete has this sorted in conjunction with MikesXS) A bit more to it, but that is the simple version

Pumps, a lot of those things on that rebuild link would normally be done on a rebuild and the prices he is charging on parts could be saved on heaps.

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Audy wrote:

Ahh so one piston is up and the other is down? Whst does doing that run in price and is there a power advantage ?

There is no power advantage,it just alters the power distribution over a wider RPM band and allows you to ultilize more of the available torque that would of other wise been spent pushing the opposing piston on a 360 firing.

pumps · Posted: July 26, 2009, 9:21 am Post subject: Re: rephase?

650skull I enjoyed reading the links you posted ,especially about Phil Irving and the history there. I even learned something. Shocked

Audy · Posted: July 26, 2009, 10:31 am Post subject: Re: rephase?

Perfect that answers and explains everything and any questions I have thank you very much

Cheers. Audy

xsjohn · Posted: July 26, 2009, 2:32 pm Post subject: Re: rephase?

Looked at all that expense......and the heat these produce in the good riding summer months and found what to me is a better way..... quite slick actually I might add......and costs about nothing if you know what your are doing...unlike any weird alternative of rephasing...ah but what would I know..........do try to keep in mind that the more you expect from these the more heat they produce.......at even a stock perspective they run too hot which hurts performance and longivity...... ah what would I know..... clatter on pilgrams..........

And most of the vibrations at expressway speeds are caused by cylinder heat imbalance from improper R/L cylinder mixtures......... might look at that idea if you have a couple of years.... Laughing

And god if I mentioned that the compression might be a bit too high causing a bunch of unnecessary heat ....some gear head might go eek....... Oh well see all of you at 100 thousand then we will discuss it...... Laughing

xsjohn

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

But John does your XS have a nasty hit like this XS2? Laughing

Gotta love those long rod motors Wink

The rephased engines produce no more heat than a normally operated XS .One advantage with a rephased motor is they produce less reciprocating windage in the lower end on the down stroke. Pros and Cons to everything I guess,just depends on what you're looking for performance wise.
www.youtube.com/watch?v=pCfY7EhEt6Q

xsjohn · Posted: July 26, 2009, 3:07 pm Post subject: Re: rephase?

Just looking to get down the road without thinking that the motor is coming to get me ....especially on the express.......suppose that doesn't matter to most........ and no one has really checked out what I am saying...... except me......and that is all that really matters.....it should slide along down the express just like it does everywhere else without all the heat or something is wrong......and if the temps are rising above 250 (which is a cringe to me anyway) then ......maybe not tomorrow but soon enough it will crap..........and just a 10 mile jaunt means nothing.........but some things can be learned there....... dang I know I have wasted my time here for sure...... and the right is gasping while you are doing all that........I'm about ready to say it but I won't .........hop them up..raise the compression .....what the F are you doing......I know.......... Laughing

xsjohn

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