Lightening a con rod, good, bad or indifferent?

[Ian Webster]

Quick pic of a friends conrod, lightened to the max.... not sure if it's the 7,5 or 15cc motor (CMB). They compete in the FSR-V classes, so 20 minute heats and 30 minute finals. So, lightening the con rod, good, bad or indifferent?

 

[Richard Dahlheimer]

Quick pic of a friends conrod, lightened to the max.... not sure if it's the 7,5 or 15cc motor (CMB). They compete in the FSR-V classes, so 20 minute heats and 30 minute finals. So, lightening the con rod, good, bad or indifferent?

I am no engine expert, but i would not even try to run the motor,with out replacing the rod. Just my opinion. Richard D

 

[Charles Perdue]

That engine is going to dissamble itself. It shoud be spectactular.

 

[Chris Wood]

YEP got KABOOM written all over it lol.

 

[carlnoki]

by the looks of the cylinder in the back ground,

it is a 91 AAC (15cc).

I would NEVER run that thing unless the rod is replaces

with a new one.

 

[Hydro Junkie]

I have to agree, replace the conrod before running. There are aftermarket rods made that are lighter, but not like that. I've seen rods that were sharpened on both sides or thinned slightly. They are good for a season, two if you run with lots of oil. To take out that much material is asking to see the rod shatter and go flying out the side or bottom of the case

 

[misshydro]

Quick pic of a friends conrod, lightened to the max.... not sure if it's the 7,5 or 15cc motor (CMB). They compete in the FSR-V classes, so 20 minute heats and 30 minute finals. So, lightening the con rod, good, bad or indifferent?

A rod like that I wouldnt trust running that at all.KABOOM!!!Then more damage is done to your motor=more costly parts to be replaced.. These motor arent cheap and the parts are just as bad in prices too.

 

[TUNLBOTR]

That engine is going to dissamble itself. It shoud be spectactular.

When you do the math (stroke length x RPM) the piston is traveling over 30 feet per second, stopping and starting, and that rod is the lever.

Spectacular is a very nice way of saying it.

 

[Al Hobbs]

The manufacturer knows what is best. They designed the engine to perform at a certain level. They make the parts to stand up to the intended use and performance. They select the materials and make the parts as light as they feel is acceptible.

The manufacturer wants the engine to run hard and last. Whoever designed and made the engine in the first place did not intend for the rod to be lightened or they would have made it lighter to start with.

Al Hobbs

 

[Kez]

The manufacturer knows what is best...Whoever designed and made the engine in the first place did not intend for the rod to be lightened or they would have made it lighter to start with.

Al Hobbs

Agreed! Recently I bought a few used engines and I was quite annoyed to find that the previous owners modified the engines. The list included drilled out mounting lugs, dremeled cranks, piston skirts, and conrods. If the manufacturers felt that such modifications would improve performance or reliability, they would have incorporated those tricks. Most engines are done on CNC machines and it would cost a couple of seconds on a CNC mill...practically nothing.

Back to the rod, I do not see how lightening it would improve performance. The engine MAY run a little smoothly IF the counter weight was light to begin with....but I believe most engine manufacturers would machine the crank counter weight to balance the piston and the rod.

I would be very upset if I bought a used engine with a rod looking like this.