XR650R Thread!

Discussion in 'Thumpers' started by JustinT, Nov 24, 2008.

  1. FlyGuy

    FlyGuy MachineHead

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    About 18 months ago I reported on the on the instillation of a Ross piston

    http://advrider.com/forums/showpost.php?p=17340346&postcount=11442

    Well on mothers day near the top of Ebbetts pass, one of the best motorcycle roads I have ever been on. I Highly recommend this road if your in the area.

    http://scenic4.org/

    The XR started bogging our of the corners, I kept on riding thinking of the high density altitude was the cause , I reached the peak of the pass 8,700 ft and warm out, I started down hill and all was good on the way once I reached 3000 ft and still had the bogg on acceleration I pulled over to try to adjust the mixture, and it died as soon as I let off the gas
    oil was leaking out of the air box profusely
    well a long story shortened. the piston cracked

    [​IMG]

    [​IMG]

    Well the ross piston made it near 14,000 miles and made the XR rev easier than the stock piston but I don't think I will buy another one.
    Looks like i am going With JE on the next overhaul
    Light weight is good til it is int and this is the case of too light.
  2. BuRPsa

    BuRPsa Finally growing up..

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    FlyGuy,

    I think 11:1 is too high to expect infinite reliability, and 14KMi is a lot already.
    I got same piston (not installed yet) but a 10.5:1, ceramic coated too, in all better and more reliable I think.
    The hotspot sits in-line with the sparkplug it seems - not a too hot grade used? And, what coolant do you use?
  3. ZXRaziel

    ZXRaziel Been here awhile

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    Flyguy , that looks like a metal casting fault , its rare but it does happpen sometimes , i have seen this before ( wiseco if i remember correctly ) . Just a bad luck really , i bet if you buy another one it would be fine , but then of course heavyer piston ( with more material /alloy ) should be stronger more reliable . Reliability its good .
    But i think the JE and wiseco are way too heavy , more than the stocker ,
    i think i will give the Ross piston a try at my next rebuild , i want to know what is the difference when running light high comp piston :D
  4. FlyGuy

    FlyGuy MachineHead

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    Using one step cooler spark plug than recomended, I have been using pre mixed honda (automotive blue) coolant. The tempature stayed below 210f But my cooling fan was fairly running constantly (might have been a help)
    I will post a different picture showing a crack on the other side of the wrist pin boss to crown area
    I believe the design could easly be improved and still be light, but the XR is not popular enough for ross to get involved?
    Additional fillet size is in order at the pin boss to crown
    I am now going to contact wossner I like there design alot, take a look at the rotatable picture in the link below of there xr 650 piston

    http://www.wossnerpistons.com/images/store/wossner-usa-inc/WOS-8575DA.swf

    I am not complaining, as for miles I live in a different neighborhood than you. In KMI there was 22,500 kmi of fun filled riding on the ross piston

    [​IMG]
  5. FlyGuy

    FlyGuy MachineHead

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    Well Id bet its a cyclical load issue due to flex
    I am also familyer of the weisco issues where the metal on the inside looked marbled indicating impurities and what you indicate happens as a cause.
    but look at the picture in my post above and it becomes more clear.
    And Hell ya go for the light weight and you wont go back.
    but check out worrsner pistons too. I am going to try to find out there piston weights
  6. rpmwfo

    rpmwfo Been here awhile

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    Based on Flyguy's info, I am going to pass on the Ross piston. I like the lighter weight, but it appears to be just too light for longevity. I agree with the cyclic fatigue from the pics.

    I do like the looks of the Wossner piston. I too would be curious about the weight of the piston relative to stock.
  7. rpmwfo

    rpmwfo Been here awhile

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  8. ZXRaziel

    ZXRaziel Been here awhile

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    I have looked at the pictures again , and you are right . there is not enough material in the critical areas and the flexing eventualy crack the piston . I like Woesner a lot and they are not overpriced , do you know how much is the weight ? ( i cannot find it nowhere to compare to the others ) .
  9. crypto666

    crypto666 Long timer

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    Buy the best connecting rod you can find, that is the weak link in that motor. Falicon are nice.
  10. XFanMan

    XFanMan Been here awhile

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    Anyone ever cut a stock tank apart and happen to know roughly how thick the plastic is at the tank top? I'm thinking about sinking a couple of capture nuts into the top edge of the tank (right under the sides of the seat) for my Sumo project. It looks plenty thick enough in the center where the seat bolt goes in but I'm not certain about the edges. I don't really want to put daylight into it if I can avoid it :eek1
  11. crypto666

    crypto666 Long timer

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    I just checked and too have Ross 11:1 in my bike, for probably close to +5k miles, but its a 102mm. Hopefully that failure isn't common.
  12. BikePilot

    BikePilot Long timer

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    FWIW I don't think 11:1 compression, even on a bore/stroke combo this large, is necessarily problematic so long as there is no detonation problem or engineering weaknesses. As an example, my old porsche 968 has a 3.0L 4cyl motor with 11:1 CR, 104mm bores and 88mm strokes. Mine has 150k miles on it now and runs just dandy. Rev range is also fairly close to that of the XR. (there are of course lots of other examples, street bikes, etc. as well).
  13. crypto666

    crypto666 Long timer

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    I agree, if it still runs on pump gas, its probably not wound too tight.
  14. BuRPsa

    BuRPsa Finally growing up..

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    Come on BikePilot,

    and nice car so btw, but that engine has a large part of the combustion chamber in the piston crown, a large indentation, plus it is a blown engine - hence it follows that those are hardly the lightweight piston type as the above Ross is, so that apple-pear comparison aint valid. Also, that engine's way better cooled than our pigs, marginal springs to mind.


    FG,

    nice pistons indeed - keep us updated if you buy one please?
  15. slickwill

    slickwill Exhiled

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    Right on both points.

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  16. cragdweller

    cragdweller Adventurer

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    Detonation causes cracked pistons. Overheating can contribute to this, but I would look at fueling (both mixture and grade) and timing first. That piston died from detonation.
  17. BuRPsa

    BuRPsa Finally growing up..

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    Actually that was my first thought too, hence my Q's.
    I believe the octane rating in the US isn't too high, so was surprised to see 11:1 mentioned. Here we've got 95, and my CRF230 with a 11:1 piston in pings low down when hot and loaded. Being aircooled this may be expected, accepted even as long as you pay attention, but on the big one I'd stay away from it. This is why I bought a 10.5:1, after all I'm not racing it.

    FlyGuy may want to look, with a timing light, at the ignition. Maybe it's out a little, a worn key maybe? Check anyway, if it pings the best piston will give way..
  18. jules083

    jules083 Long timer

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    Installing new swingarm, shock, and linkage bearings tonight. Obviously fill the bearing with grease, but should I put anti-seize on the outside of the bearing or just more grease?

    I have the honda shop manual so hopefully I don't have any surprises.

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  19. BikePilot

    BikePilot Long timer

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    I think Porsche made 14 blown 968s, which, sadly, mine is not. It's N/A. I wouldn't call the XR650Rs piston a lightweight type piston, but that's a relative thing I suppose. Anyway, just one datapoint.

    US octane is roughly the same as ROW, it's just commonly measured differently.
  20. RideFreak

    RideFreak Torque Junkie

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    The problem with the XRs bottom end isn't the rod, Honda had a run of poorly built cranks that caused a failure of the Big end thrust washers. Plenty of SM guys run them much harder than we do. Once the washers start going bad it's a very short time before the bottom end follows. Results are the same though, once it happens the bottom end is toast.