Thinking about an aftermarket connecting rod.

Technocyclist

Technocyclist

Motorized Bicycle Senior Technologist
Hi All,

If you're thinking about an aftermarket connecting rod, then you might want to read this article first.

http://www.faliconcranks.com/Making%20the%20Connection.pdf

Well, in summary, basically, there are different designs of connecting rods and different materials. Making the connecting rod lighter can increase up to 1000 RPM without causing damage to the engine, but I dunno if this applies to the China Girl. This would also lessen the stress on the needle bearings and piston.

So, I'm thinking if I replace my connecting rod with an aluminum alloy one, it might cause an out of balance rotational forces to the cranks... hmmm, but I think it's worth to try.

I'm also thinking of drilling holes on the stock connecting rod to make it lighter, but this would sacrifice structural integrity...

what do you guys think? Has anyone tried reducing the weight of the connecting rod?

BTW, so far I've encountered 3 sizes of connecting rods, but correct me if I'm wrong. These are: ZAF 50, ZAF 60, and ZAF 80. The higher the number, the longer, and therefore heavier. I've used ZAF60 and ZAF80. My Engine with the ZAF60 seems to have more power and runs smoother. Engine with the ZAF60 has a longer piston. So if you're ordering parts, check out the number on the connecting rod first.

With this in mind, since there are different sizes of connecting rods, and all (I assume) are using the same cranks and counter balances, so I think it would'nt hurt to replace the connecting rod with an aluminum alloy. Well, it might hurt my budget though... :)

There had been a lot of threads about porting and crank balancing, but I guess the connecting rod is equally important... :)
 
A lighter rod might help the inherent vibrations of the 66 cc motor. The 66's are unbalanced due to the Chinee simply boring the cylinder for a bigger, heavier piston and doing nothing about the balance.

A bigger, thicker aluminum rod would also take up more volume in the lower end, always a good thing.

Unless the lower bearing has a steel insert I'd worry about wear on the big end of the rod, I'm pretty sure it would have to, aluminum does poorly in the load bearing moving part department.
 
Those parts are reciprocating at an extremely high rate and changes will lead to catastrophic failure. The question is, at what point ?
I admire your devotion to the gods of speed & horsepower. LoL
rc
 
I'm not sure if you'll see an increase in rpm that would be significant. Our engine's are hampered by breathing not connecting rod weight. Give it at try and share results with us.
 
Thanks!
You guys are great!!!
I haven't heard 'shot peening' mentioned in a long time.

The thought of opening up the transfer ports brings me back to realize everything done to an engine must be done in concert with other related mods after a bunch of consideration and experimenting.

I suppose that is among the reasons why the first mod is always an improved cylinder head with squish band.
A pipe will bring lots of power for the buck, but the associated jetting process becomes very critical.

Any way you look at it, these are great little engines to experiment with!

Best
rc

Here's a neat engine! Bugatti TA-2 for a Peugeot.

37051d1307801881-outbike-t72a-bugatti.jpg


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OMG. that engine is sick!
looking @ over engineered machinery is like porn.
anything bugattii is especially sexy & expensive.
tell me you wouldn't want two of these engines.
a "trophy" one pampered. the 2nd one to get dirty.
 
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