Does polishing the motors crank connecting rod help performance?

[zean]

Wow! 10,000rpm with a 60 foot skid. Your shoulders and balance must be in excellent condition. I’m old. That sounds scary. That sounds like 50mph. I’ve done 50 on a motorized bicycle regularly a few years ago. I like it. The bikes were purposely built for 50. I appreciate your sincere insightful posts. Thank you.

 

[Street Ryderz]

Did you just use a belt sander? I was probably just going smooth it out with fiber Dremel pads. I don't want to risk my dumb a** messing it up.

I did mine with a die grinder and carbide bit, but had the crank separated and rod removed at the time, you could do it with a rotary tool and the crank still together just tape up the big end real well to keep the filings/shavings out of the bearing and use brake clean to flush it out after done.

 

[GW's Motorized]

I did mine with a die grinder and carbide bit, but had the crank separated and rod removed at the time, you could do it with a rotary tool and the crank still together just tape up the big end real well to keep the filings/shavings out of the bearing and use brake clean to flush it out after done.

I still don't want to f it up

 

[Street Ryderz]

Wow! 10,000rpm with a 60 foot skid. Your shoulders and balance must be in excellent condition. I’m old. That sounds scary. That sounds like 50mph. I’ve done 50 on a motorized bicycle regularly a few years ago. I like it. The bikes were purposely built for 50. I appreciate your sincere insightful posts. Thank you.

Yeah it was over 60 actually but my ride has me sitting very low and bars are almost level with my shoulders and I sit upright so straight arm's just had to control the fish tailing LOL.

 

[michael whiteman]

The hot rod practice from days of old regarding polishing connecting rods was done to hopefully make the rod more reliable. Polishing eliminated slight surface imperfections from whence stress fracture cracks originated. The fact that they just look pretty and, maybe the oil will not stick as easily, are just secondary observations. One thing to be aware of when polishing a connecting rod is the direction of travel with the grinding wheel. Use a circular sanding drum and gradually reduce the grit. If nothing else it will give you some peace of mind and there is only one, not eight. LOL

 

[GW's Motorized]

Just curious, what is the most HP someone has squeezed out of one of these engines. I'm guessing that some people have done insane builds with these. I've seen engines with a kx80 cylinder, but I wouldn't count that due to the amount of machining necessary, I'm more of wondering about saw or minarelli builds.

 

[ImpulseRocket]

A word to the wise on polishing conrods with these China girl engines I would say yes a slight benefit might be had but if you are talking about any other decent quality motor never touch the connecting rods with anything abrasive they would be shot peened which greatly increases the fatigue strength and sanding or polishing or deep scratches would greatly reduce its overall strength.

Peening is also preferable for balancing reasons since it doesn't remove material. It also creates a more uniform surface "tension" in the material (Work hardening).

 

[michael whiteman]

You're right. Shot peening is done after polishing. It basically relaxes the molecules in the metal. The amount of metal removed from polishing is negligible. If you're worried about that, you'd better get a stronger rod to begin with. Besides, if you're building a performance engine you will want to rebalance the whole assembly after these modifications are complete.

 

[GW's Motorized]

You're right. Shot peening is done after polishing. It basically relaxes the molecules in the metal. The amount of metal removed from polishing is negligible. If you're worried about that, you'd better get a stronger rod to begin with. Besides, if you're building a performance engine you will want to rebalance the whole assembly after these modifications are complete.

I was going to use a yd100 rod, so it's a higher quality part. Also I have no idea what peening is.

 

[GW's Motorized]

Would drilling the rod to lose weight a good idea, or would it just waken the rod too much?