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  1. #11
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    Hey,
    Don't know about the YZ hardware, but there seems to be a consensus with CR500 riders (cr500riders.com and bannedcr500riders.com) that Pro-X pistons are to be avoided due to poor architecture--the sides of the pistons are open to the exhaust port, allowing the transfer charge to blow straight out when the exhaust port should be sealed. Also, alot of those guys are getting away from Wiseco forged pistons because they seem to seize easier--the forged aluminum is apparently stickier than cast.
    That's why I'm putting a Vertex cast piston in my '85 CR500. All reports I have gotten is that reliability is similar to OEM.
    Hope this helps!







  2. #12
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    Geez, are we going down the crapper? What next, testimonials for namura and magnum brands? Forged are Stickier, really? And to think of the money I could have saved, never changing my oil in a car with over 200,000 miles on it???? Is that a sign of quality, or dumb luck? I would rather believe its how the engine is getting used/abused. Doing a search seemingly did not work, we will now roll over and be another hear say site? Anybody else up for hear say talk, or dig up the facts, forged are miles better than cast. Stickier? Some new engineering word? Vintage Bob



    m y   s i g n a t u r e:


    WHEN IN DOUBT, GAS IT! : 83CR480R, 97CR250R, 00CR250R 05CRF450

  3. #13
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    im going with cast since i work in a foundry

    anybody have a pattern for a piston I'd like to pour my own out of waspaloy

    http://en.wikipedia.org/wiki/Waspaloy



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    if you're gonna do something you'll regret in the morning its always best to sleep in

    if my ex-girlfriend was half as dirty as this president there wouldn't be an ex in her name

  4. #14
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    Forged pistons are generally used in high perfromance applications because of their greater strength over cast The grain structure of forged metal tends to follow the shape of the piston (because it was hammered into shape) and the cast grain structure follows one line. Forged pistons expand more than cast when heated, so they need slightly looser tolerances when cold (which can cause the forged piston to rattle a bit more at start up).

    Regardless of which method is used, it still depends on the manufacturer to create a quality product and the installer to intall it correctly.



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    aka Crazy Russian

    Two strokes are trail bikes
    Four strokes are motocross bikes

  5. #15
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    Did you have a bad Easter weekend Bob?
    If my comments aren't useful, then disregard them.




  6. #16
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    Here's a good thread on forged vs cast. It's amazing how search works
    http://www.dirtrider.net/forums3/sho...threadid=35945



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    If you see me coming up to pass you then you better move out of the way cuz I'm going the wrong way!!! :-O

  7. #17
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    but does a harder piston (forged) wear the nikasil coating quicker than a cast piston?




  8. #18
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    Quote Originally Posted by expansion chamber
    but does a harder piston (forged) wear the nikasil coating quicker than a cast piston?
    I highly doubt an aluminum piston, whatever can be done to it, could EVER wear a harder plating out. Running a loose piston has the effect of pushing the material behind the plating out of round. I doubt it would on a sleeve though, thats why I asked. Loose a bearing, ring or cir clip and say good bye to the bore. Most of the seemingly horrible looking bores, thats just aluminum flashing rubbed onto the plating. A scotch brite pad and oven cleaner takes it right off, back to the original hash mark. If a guy wants to run long, put the sleeve in, they even claim to have chrome and some alloy sleeves, and they can plate sleeves. Only 1 issue, they still wear quicker than oem or better plated aluminum. The heat dissipation and expanding and contracting differences. 3 races or 7.5 hours, thats what my 97 CR250 suggests. I know darn good and well that I can go longer, minus any debris catastrophes getting by the carb. I also know that James Stewart could NEVER get that much time out of a top end. His would do well to last 30 minutes plus 2 laps. Wiseco, namura, vertex what ever, they are not going to tell you much longer than the manual. 5 to 10 hours on a 250, the rings are gone, less for the smaller bores. And that is running 32 to 20:1 premix ratios! My recent experience with used dirt bikes has pushed the limit on what gets said about how long parts last Plynn 41, proper maintenance and these bikes would last a lot longer, and be a lot cheaper in the long run. Abusing the maintenance schedules, I sure do not want to buy a bike from someone like this again! Not too many 2 stroke ex-racer bikes around anymore. Vintage Bob




  9. #19
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    Whether it's a forged or cast piston it's going to wear the same. They are both aluminium and one is not harder...or softer than the other. They both will wear out long before the plating.




  10. #20
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    Seems like the forged doesn't grenade, and I hate installing crankshafts! I think the one guy had it right, if you're not changing your cast piston after every hard long run, then forged would last longer.



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    '06 RM250 '03 CR250
    Columbia, SC

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