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Rephased 1979 xs650

Discussion in 'The Garage' started by Tony Jara, Jan 11, 2017.

  1. Tony Jara

    Tony Jara XS650 New Member

    I'm mulling over the want as opposed to the need of rephaseing my engine....and all that it entails....understand the basic concept....but no where have I found a concise step by step materials list(Hughshandbuilt has provided the inspiration)and I have a climer manual.
    Do I have to bore out to make larger the round orifice where the pistols go in? I know that the crank/camshaft needs to be serviced....and ignition,charging systems.
  2. Its definitely not a need. The TECH section has a sub-section on re-phase. Go there and read. Do you have a spare $1000 dollars?
    I see no advantage to it........................there is no more power added to the engine. If you want more power, you would be better off by going to the 750 cc increase.
  3. CoconutPete

    CoconutPete 79' Special & 78' Standard

    Hey Now!
  4. Tony Jara

    Tony Jara XS650 New Member

    Wow!....I will check it out....and no I don't know what "spare" is.....more probable to earn to gain 1000...my main goal is for endurance not speed
  5. Tony Jara

    Tony Jara XS650 New Member

    I meant pistons....spell check doesn't work on my phone....
  6. Rephasing has been touted as a way to reduce the vibes on the parallel twin XS650. The vibes are not removed but shifted to another plain and become a more of a buzz that does not transfer to obvious visuals, like the side mirrors.

    Rephasing is a must if you are going to Race the bike competitively because with the vibes on a different plain the engine can rev freely.

    many who have done the 277 rephase say they would not do it again. A friend who has a 277 rephase says after a couple of hour the vibes affect his hands enough to make it uncomfortable.

    There is a 277 or 270 rephase.

    As pointed out do some reading and research. This topic is to large to post a quick answer to give you all the facts.

    Hugh got all his information from the Australian XS650 Club site. We, (as a club) did major developing and the successful implementation of the 277 and especially the 270 rephased XS650 motor. This theory had been around for a long time as per the article posted in one of these links.

    http://www.xs650.org.au/Technical Info/smoothness.htm
    http://www.xs650.org.au/Technical Info/rephase angle.htm
    http://www.xs650.org.au/Technical Info/tech5.htm

    This what can be achieved when doing a 270 rephase for an XS650 Racer
    http://www.xs650.org.au/Club Racer Stuff/Club Racer.htm
    A club member who Has his own Racing bike is the NSW Champinship winner this year for the in the P4 category and he has taken the no 1 spot for the P4 up to 750cc and P4 up to 1300cc Classes. He is racing and beating X Wayne Gardner motor GP racing bikes.

    I will add his bike has a 750 kit
    Last edited: Jan 11, 2017
  7. Jack

    Jack XS650 Junkie

    If your goal is to reduce vibes,rephasing isn't the only recourse. If rephasing is your goal,look up rephasing by member Kopcycle(spelling). Don't get the crank fully welded either,despite what one person might say. If a bottom internal problem occurs,it would difficult to separate if at all. Listen to the Aussies on this matter, they know their shit when it comes to the XS
    Last edited: Jan 11, 2017
    hooser likes this.
  8. hooser

    hooser XS650 Addict

    650skull , who was the 1st to start the rephrase?
  9. Here's a sample of the endurance of the stock XS650:
    xjwmx...........50,000 miles
    jetmechmarty...............53,000 miles
    motor650b..............62,000 miles
    cmyoch.................65,719 miles
    xs1961.................90,000 miles
    cowboy3669...............100,000 miles
    spockwerks.................114,000 miles
    TwoFitty......................120,000 miles
    It seems the stock (360 degree crank) engine is very durable.
    Last edited: Jan 13, 2017
  10. MaxPete

    MaxPete My float bowls are leaking again!

    Agreed - this isn't about power - because rephrasing does not affect the displacement, combustion chamber size or shape, cam lift or timing (except for rephrasing the valve timing itself) or the exhaust or intake tract geometry of the engine or the fuelling system (carbs) - and those are the things that affect engine power output.

    It is about the sound and "feel" of the bike...and I guess everyone has to judge the value of the benefits of that for themselves.

    The stock XS650 is a 360 degree twin engine which means that the pistons go up and down together and while one cylinder is on its power stroke, the other cylinder is on its intake stroke. Not all twins are 360 deg. by the way. The Brit bikes (BSAs, Triumphs and Nortons) are 360s, but the smaller Honda twins (CB 350 and 360s for example) were 180 degree twins, as I recall it.

    As for the two types of rephrasing: 270 degrees and 277 degrees, the difference is that 270 would give a potentially better dynamic balance of the forces in the engine, but the 277 degrees modification is easier to accomplish because "all" you neeed to do is take apart the crankshaft and shift one cylinder assembly by a few splines (and install a camshaft to suit that new piston timing layout) and then press the crank back together (and possibly weld it). It just so happens that this process yields a 277 degree crank. Doing a 270 degree crank would require new crankshaft parts with revised spline spacing - much more expensive for a relatively small difference.

  11. MaxPete

    MaxPete My float bowls are leaking again!

    Danged spell iPad checkers!!!! :oops: Let ME do thing thinking around here!!!!

    It's should be "rephasing" and NOT "rephrasing".
  12. hooser

    hooser XS650 Addict

    Has anyone come up with some dyno numbers on these just to see where the power shifts in rpm range.
  13. What is your experience with rephrased motors and the application to the US racing scene. You must have had a lot of discussion with people in your line of business, way before the XS650 became the flavor of the month .
  14. Okie

    Okie XS650 Addict

    One advantage of a 270° engine ( or 277° if you go Hugh's economy route ) is that when one piston is at TDC, the other piston is at or near maximum velocity, as apposed to a 360° crank where both pistons move together at the same speed. It must smooth the delivery of power, or Triumph never would have done it. I don't think it makes more power, just changes how it's delivered. It's really totally un-necessary, the XS has legendary reliability.
  15. hooser

    hooser XS650 Addict

    Nothing in the years I have been involved. In this day and time the riding skills between racers (vintage ) is so varied. There is know real way of telling if it is the bike or the rider and in my experience it is the rider.
    Here is a true story, a good friend took his 250 Brakeless BSA and won the 750 brakeless class. He was riding against some fast guys also. He always told me 80mph is 80mph, to win just go 81. He always told me If you have a bike that handles and can keep it wide open, you can beat the guy that shuts down for the corners.
    What you said about your friend in Racing down there , he may be like my friend just fast and could win no mater what he was riding. A good test would be to have him and the 2nd place rider change bikes
    Last edited: Jan 12, 2017
    FLEA likes this.
  16. fredintoon

    fredintoon Fred Hill, S'toon.

    Hi Tony,
    spare as in "hey mister, got any spare change?"
    If I had a thousand dollars to spend on an XS650 upgrade there's many other things I'd buy before a rephase.
  17. Hooser, True on the rider as opposed to the bike. In this case he, (Ivan) hes been riding the same bike for a number of years and has been developing his XS along the way. I would have to say it is probably a combination of the 2 as he gains more experience in conjunction with the development of the bike. He has been racing for a while though.

    He has had a major input with the build of our club racer, (which has taken 8 years to build with club donations and voluntary work), and Ivan has said working on the club bike has given him a lot of knowledge he has applied to his bike to make it that much more competitive. Probably those little things that you don't normally think about and the club bike has been an opportunity to do some experimentation. Ivan makes sets of high ratio primaries, the latest set has weight reducing holes, before that gave them roller bearings, before that the were brass bushings. As you would know, less friction and combined with less weight is going to help get to that 1 KPH/M
  18. hooser

    hooser XS650 Addict

    Tony , here is the bottom line with this.... as you have already found out here on the forum some like it some don't.
    You have to decide on cost verses what you will get. In theory a smoother ride, but with my well tuned 700 I can let idle and see what is behind me in the mirror. So I op for performance . Figure what it will cost for a standard rephrase 43hp motor, or a 56+hp. You can have more power for less.
    Cam $125.00
    700 pistons $305.00
    Bore cylinder $150.00
    Spring set.$155.00
    If you do want to go with the rephrase , check out the powerdydnamo ignition at www.powerdynamo.biz
  19. Jack

    Jack XS650 Junkie

    A well tuned XS650 - 750 will run smoother when the reciprocating mass of the rods small end is reduced along with addition of a longer rod like CR500. Jim Schmidt(Spelling) has been doing for years racing the Norton's.Granted locating a light weight piston for a 750 could be difficult but not impossible as a piston
    diet would be in order along light tool steel pins. Long rod it and the door opens up to pistons light as
    220-246 grams and lighter with some grinding for street use. Enough on long rods as you get the picture.
    hooser likes this.
  20. Material list for a rephase.

    If the crank bearings are good they can be reused. ........No cost...............If not, (you would need them anyways on a rebuild), a new set of crank bearings

    Cam, needs to be rephased............ Cost. Varies............ depending on the supplier and what type of cam got.

    Ignition system. ..............Cost varies ................ powerdynamo, Is also a charging system. You have to weigh up if you.... want to or need to.... replace the the charging system..............Pamco would be the low cost option as an ignition system only.................there are others as well.

    Coils. need 2................Cost varies.

    That's about it for parts.......................Any upgrades in CC, cam profile, head work and if the crank bearings need to be replaced + the cost of getting someone to do the mechanical work is the expensive part. Again this also varies depending on who does the work and how much you do your self.

    If your motor needs to be refreshed, then the cost of, cam chain, guides, pistons, valves, and any machining is already a necessity so these things should not be factored into the cost of the rephase as that is an extra.
    Last edited: Jan 12, 2017

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