Some info on Chinese billet rods

[65ShelbyClone]

I bought a ~$36 billet connecting rod for a GX140 I'm playing with again and thought I would share some of my observations.



First and foremost, the bolts are trash and should be replaced. Lots of people break them and even RBG did. My hypothesis on why is that the threads were rolled right into the necked-down section of the bolt shank, making the minimum diameter even smaller and putting a bunch of stress risers in it. If you want to read about a neat engineering topic, look into notch strengthening. This bolt had it until they cut threads through part of it. You can't replace them with ARP bolts for an ARC rod either because these are metric. They're also M6x0.75x30mm, which is surprisingly hard to find locally and even on Amazon in a class 12.9 socket cap screw.



The dipper oil hole was also filled with metal chips/swarf/etc from the machining process. If someone misses this on assembly, that junk is either going to block the oil hole where the bolt intersects it or go into the bearing. On of the chips is there next to the bolt above, but this is how I found them:




The bearings are also covered in swarf, but that's less concerning to me because it's soft and easily removed.

 

[panchothedog]

So you've kind of covered all the bases. The $36 Chinese rod is not quite JUNK, and with a bit of work, and searching for the impossible to find quality metric bolts, you might just get it together. Then comes the thought in your head ( about the time you have it really wound up tight ) I wonder how much dirt or sawdust that Chinese guy stirred into the pot of aluminum to yield a little more. Honestly, in my opinion, you couldn't have made a more powerful commercial for the genuine ARC product if you tried. So much of this kart stuff, we don't have much of a choice where it comes from. Glad to buy the quality American product when I can.

 

[Hellion]

You and Edwin both doing the needful reviews on these rods made out of ultra special Chinesium.

ARC rod copy for GX340/390/predator 420

https://www.ebay.com/itm/406131589968 Rod looks decent enough. Bolt are questionable. Bearings are questionable. -But Ill worry about those questions later if something blows up.

www.diygokarts.com

Many thanks.

 

[65ShelbyClone]

So you've kind of covered all the bases. The $36 Chinese rod is not quite JUNK, and with a bit of work, and searching for the impossible to find quality metric bolts, you might just get it together. Then comes the thought in your head ( about the time you have it really wound up tight ) I wonder how much dirt or sawdust that Chinese guy stirred into the pot of aluminum to yield a little more. Honestly, in my opinion, you couldn't have made a more powerful commercial for the genuine ARC product if you tried. So much of this kart stuff, we don't have much of a choice where it comes from. Glad to buy the quality American product when I can.

I knew going in that the metallurgy is an unknown and just kind of assumed that these rods are not 7075 aluminum like an ARC. The pictures of failures all looked to be from the bolts breaking. I figured that even if the aluminum is just 6061 or something, the strength of it is still adequate, at least for the short-term.

ARP's website also doesn't list M6x0.75 bolts. Even class 12.9 (~170,000psi) M7 bolts are easier to find than that, which is what the stock rod uses. They chose the worst bolt size possible. Maybe it was intentional.

This is another case of low cost being a poor value, which is typical of Chinese knockoffs like this. The $65 ARC knockoffs all over Amazon and eBay are an especially bad value when another $20 will get you the real deal and support an American company. Many of the no-name performance cams are also fakes; most or all of the "265" grinds on Amazon are actually stock .220" lift parts worth $5. Plenty of positive reviews, though...

 

[Thepartsguy]

I am looking for a 212cc to follow red beards Chinese parts build and I will actually test it to the beyond without care if it it breaking just to see what these engines are about.

I see $600 $700 engine builds going around a track in class races and everytime I think to myself I could smoke‘‘em all with a mild built Briggs. They seem to be rpm’ing to the moon but they don’t in any of the videos I have ever come across appear to be going very fast at all…