Long vs. Short Rod Crank
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  1. #1
    Senior Member christph7's Avatar
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    I've got an 88 TRX 250R and am getting the ESR 330 powervalve. I plan on replacing the crank while I have the engine apart and am wondering about the advantages and/or disadvantages of the long vs. short rod crank. I'm thinking the long rod will offer more torque while the short rod will rev out more quickly and perhaps offer more overrev--which is what I want. Also, with the short rod I won't have to use the spacer plate. Does this sound right? Thanks.
    1982 ATC 250R
    1984 ATC 250R
    1986 ATC 250R
    1988 TRX 250R
    1989 TRX 250R

  2. #2
    Senior Member 2R's's Avatar
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    remember the difference is small check here, http://www.r-central.net/trx250rforums/ind...?showtopic=3894

    if any added torque it would be pretty hard to feel a difference IMO,..

    1 thing to remember is with a spacer plate there is more chance for a leak ..= not good
    yet OEM short rod is no longer being made,..but I do agree about quicker revs on a short rod ,thats what I am using ,& found it to be a great set up !



    she's a MX racer
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    "Those who dance are often called crazy by those who cannot hear the music"

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  3. #3
    Senior Member christph7's Avatar
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    Thanks for the site reference. I came across that weeks ago but recently did a search and couldn't find it. Yeah, I just found out that the OEM short rod crank is no longer available. My options are to get a Hot Rods crank or have the short rod installed on my OEM. Any comments on the quality of Hot Rods cranks are welcome.
    1982 ATC 250R
    1984 ATC 250R
    1986 ATC 250R
    1988 TRX 250R
    1989 TRX 250R

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  5. #4
    Senior Member 2R's's Avatar
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    my 2 cents,.. I dont trust them !!



    she's a MX racer
    http://mxptv.com/video/rider-session...loretta-lynns/

    http://www.photoreflect.com/pr3/thum...aspx?e=5567552
    http://rides.webshots.com/album/573945126OHEsjN

    "Those who dance are often called crazy by those who cannot hear the music"

    "the man who follows the crowd will usually get no further than the crowd
    the man who who walks alone is likely to find himself in places no other has been before" A Einstein

  6. #5
    Banned NOS_350x's Avatar
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    Rod angle is a bit better on a long rod they also with the spacerplate have more crankcase volume, but IMO a short rod seems to rev better. Just what ive noticed.

  7. #6
    Senior Member 2R's's Avatar
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    the concern about rod angle has been LONG dismissed.. ( anyone know the history about it ?)

    what does more crank case volume do ? anyone wanna try that ?



    she's a MX racer
    http://mxptv.com/video/rider-session...loretta-lynns/

    http://www.photoreflect.com/pr3/thum...aspx?e=5567552
    http://rides.webshots.com/album/573945126OHEsjN

    "Those who dance are often called crazy by those who cannot hear the music"

    "the man who follows the crowd will usually get no further than the crowd
    the man who who walks alone is likely to find himself in places no other has been before" A Einstein

  8. #7
    Senior Member SHOWNGO250R's Avatar
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    the concern about rod angle has been LONG dismissed.. ( anyone know the history about it ?)

    what does more crank case volume do ? anyone wanna try that ?
    Lol!

  9. #8
    Senior Member Burns350R's Avatar
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    Short rod/long rod should rev the same. They have the same exact stroke. Just different rod and piston lengths to accommodate each other to have the same deck height.
    (MX) TRX 363R 02- Laeger Narrow Frame/CR500 Link,Motowoz, Roll Design +4, RPM +4 axle, LED 363 +4 Stroker, 38 A/S carb,Rath Signature Series,CCP

    (XC) TRX 370R 86- Stock frame(gusseted),No link rear, JD MGC +2 Arms, Motowoz shocks, RPM XC Axle, LED 370, 38 A/S carb, Rath Signature Series

  10. #9
    Banned NOS_350x's Avatar
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    the concern about rod angle has been LONG dismissed.. ( anyone know the history about it ?)

    what does more crank case volume do ? anyone wanna try that ?


    Im really curious when this was dismissed? Short rod puts the piston to rod angle at a harsher angle, Causing the piston to be pushed further forward or pulled backwards. Causing extra wear on the cyl walls. Now this isnt really bad in small engines, you take a short rod and put a 330 on it it wont last as long as a long rod.

    Crankcase volume, Ever added a reed spacer, Ya they dont do much but it does make a bit of a difference. Now think about how much more that spacer plate is doing compared to the reed spacer.

    Burns, they are the same deiplacemnt, wiht the same bore and stroke, You arnt going to get much of a difference, but there is more ricipicating mass wiht a long rod, I personally feel that is where the difference comes from.

    I belive, these little things wont make or brake a bike, but you add all the little things together and it all adds up to make a difference to get a motor to where someone likes it. Also racing, I want things to be perfect for me, that is why i try things.

  11. #10
    Senior Member christph7's Avatar
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    Short rod/long rod should rev the same. They have the same exact stroke. Just different rod and piston lengths to accommodate each other to have the same deck height.

    If they have the same stroke then why do the 87-89 need spacer plates when you use an aftermarket cylinder? I can see why you need one if you use an 86 piston on an 87-89 crank because it adds 5mm to the overall height (TDC).
    1982 ATC 250R
    1984 ATC 250R
    1986 ATC 250R
    1988 TRX 250R
    1989 TRX 250R


 
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