2.5 drag crank polish

[hollywood120]

I have a 2.5 300 drag crank and connecting rods I want to lightly clean up and polish prior to assembly what's the best recommended grit and material to use on the crank and would the rods use the same grit also. I have used a 3m micro film 300 grit in other engines with out any issues but that's a little on the coarser side I was wondering if there is an actual specific grit to use for best results on this particular engine. Thanks Frank

[25two.stroke]

I use some 320 crocus cloth and have been using it for years. That being said, I told my friend Tim to grab some 320 from his local hardware store when I was visiting him and we were working on some of his motors. When I got to his place and started using the 320 he and I both looked at what it was doing to the crank and decided to stop. It was not the same 320 that I use. You could feel the grooves with your fingernail. Do not do that. My 320 must not be the same as other 320...what I use here seems like the equivalent of 600 sandpaper very fine almost like a hone.
If the crank looks good then don't touch it imo. If the rods are slightly discolored then hone them. If they have marks where bearings sat with water and turned them black I toss them out.

[hollywood120]

No everything looks fine on the crank and rods just some really fine scuffs like circular lines probably from poor cleanliness in the environment or shop during assembly you can not feel them but you can see them like buffing more shiny then the rest . the crank is new with only 25 hours on it . So I thought just like everything else do a clean up and prep work like you do on the cylinders walls with cross hatch for the rings seating during break in . Being I am putting all new bearing through the engine so why not prep these parts also with a super fine cut to help the hold the lubricant better to the parts at higher rpm,s nearing 10,000 range. The 3m material I use has 40 microns witch relates to approx: 443 grit polishing finish I was going to touch it up with that and then maybe final dress it with a 30 micron witch will put it at a 601 grit final finish. and then there also is a 20 micron witch is a 923 grit finish but I don't think it needs to go that far . I think 30 micron will probably be the final ticket for best results. If you get it to smooth the bearing can under hard excelleration and then quick deceleration will chirp like a heavily worn out Motor like the bearing can't catch up the crank and slide causing the chirping till they regain speed with the crank.