Rod Comparison
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Last updated: 5/7/07

In the rebuild of the crank for my Honda CRM250 I considered the characteristics of three rod candidates.  The stock Honda rod, a replacement ordered from Leisure Trail in the UK, and a rod manufactured by Wiseco in the US.  The stock Honda rod I'm using for comparison suffered a big end bearing seizure, so a new one would have to be obtained from Japan if I chose to go that route.  The replacement rod supplied by LT was not a Honda OEM part, rather it looks to be a Maico replacement part that shares similar dimensions with the OEM Honda part.  The Wiseco rod is cataloged as a replacement for the Honda TRX250R (P/N WPR156) and can be ordered from their website.  See below for details:

The stock rod is on the left, the LT replacement is in the middle, the Wiseco TRX250R rod on the right.  As you can see the Wiseco rod is significantly lighter than either of the stock or LT rod.  It fact, the Wiseco rod is 53 grams, or 22%, lighter than the LT rod.  There are other important differences also as noted below.

Again, the stock rod is on left, the LT in the middle and the Wiseco on the right.  Note that both the stock and Wiseco rods each have two lubrication ports located in the top of the bearing journal while the LT rod has none.  And although it is difficult to tell from this picture, the bearing journal in the LT rod is not bored on center.  Also of note, the LT and Wiseco rods have a 22mm bearing journal, the stock rod is 23mm.  The difference is allowed for with the use of an alternative bearing as noted on the Piston Comparison page.

The big end bearings, in the same order as above.  The stock and Wiseco rods benefit from a chamfered lubrication port allowing a more uniform dispersal of lubricant to the bearing surface while the LT rod uses a more rudimentary straight-cut port.  The bearing journal for both the LT and Wiseco rods is 31mm while the stock rod is 32mm.  In order to fit the non-stock rods a 25mm ID x 31mm OD x 17mm L bearing is used with the stock sized 25mm W x 59mm L pin.  The pin and bearing that comes with the WPR156 Wiseco rod kit will not fit, (the pin is 24mm, the bearing 24mm x 31mm).

Having gone through the above analysis I couldn't bring myself to use the LT replacement rod and opted to use the Wiseco item based on weight, quality of manufacturing, and lubrication allowance.  I've since got the bike back together had a chance to run it a fair bit.  With the cylinder blueprinting and the cylinder and crank work, and the addition of the Boyesen reeds and the FMF silencer the motor has noticeably more power.  It has an increased willingness to rev and a stronger mid-range punch.  It also feels to carborate more cleanly on the bottom, and is easier to start as an added bonus.  All in all well worth the effort.

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