250R benefits of polishing the con-rod

[hrc85250r]

hey, im building my drag motor, and i was thinking about polishing my new rod before i do up the crank...does anyone know if its actually worth the time to polish the rod? ive seen it in a few 2 strokes, namely our indy500 stroker race motor but we didnt have the work done so idk......thanks guys....

[vintagemotorsports]

I cant see what you will gain by polishing the conn rod , i quess if you were able to see it , it may change the fuel mixture swirl in the crankcase but I personally dont think its worth doing .

[slothminx]

A normal as cast rod will have lots of scratches, and roughness to the surface. Each of these is a potential spot where the rod could break. By sanding the rod to a flat finish going lengthways with the rod and then polishing the rod to a mirror finish you are getting rid of all the potential breaking points (stress risers) resulting in a rod thats less likely to break and when your spinning it at 10000+ rpm will has less resistance through the air down there.

[Mr. Sandman]

Slothminx is correct. Typically on high performance motors, the parts such as the rods, crank, etc. are first magnafluxed, polished and then shot-peened to identify microscopic cracks, stress points etc. and the polishing and shot-peening will minimize and strengthen the failure prone areas.

Is it worth the added time and cost for your motor? Only you can answer that question

[hrc85250r]

thanks sloth and sandizzle manizzle....i was looking at my new rod earlier after i posted and i read on the bag that its in that its already shot peened. i dont knwo if its even worth polishing after the shot peening. i think the shot peening itself would take out any surface stress there is....ill talk to my professors when i go back to school, they build race motors so they can help me out too....thanks again guys

[HRC1]

i never even thought of doin it to a bike motor, but i can't see where it would hurt, basically your taking the casting flash off the rod that runs up it's length, and smoothing it out. And like was said before, eliminating stress risers where a crack could form. I'd just use a die grinder with a carbide bur for and "high" spots fallowed up with a flapper wheel. I'm gonna have to remember to do this next time i have one of mine apart, i do it to my car rods, and i see no reason not to do it to a atc rod as well...

[KZXT650]

use a small drum sander on a die grinder, stay away from carbide burs for this application as they can easily skip and cause damage to a spot you dont want damaged,
by the way, what kind of rod did you get, who makes it? when my kx 500 was donewe used one of those hotrods, and i polished it to remove the little bit of stress risers that were still on it before sending it, the piston, and the crank out to be assembled, welded and balanced.

[hrc85250r]

i got a hot rod, and it is baiscally polished right now, i mean i can almost see myself in it, and they are already shot-peened when they make them, i might just take a polishing wheel on a drill and clamp the drill in the vise wide open and polish it that way, just to do it. i dont think this rod is gonna blow becuase they are so beefy, but what the hell....might as well....

[KZXT650]

yeah they are beefy for sure, gotta love it. the one in my kx engine was bought about 5 yrs ago and it was sweet but i couldnt almost see my self in it like you say, guess they started doing better clean up on them, good to know. i figure my engine should be able to spin a good 13000 r's and hold together, hasnt been fired yet, its sleeping wrapped up with silicate packs in my bedroom closet ,lol.