Are connecting rods and caps paired?

[berni29]

Hi There

I know some conrods and caps are actually created from the same casting, so have to stay together for a correct fit, but is this true for the 125E rods? I think not, but do not know for sure.

I do not know the history of my engine and it came basically in bits, so cannot be sure that they have not been mixed up at some point in the past. Is there any way of telling?

Thanks in advance!

Berni

[miked]

Are they not usually lightly etched with the cylinder numbers on the rod and the cap at the side.

[berni29]

Hi Mike

That is interesting, but mine do not seem to carry such markings. The caps and rods have been machined somewhat down the sides, so I may try and match up the machining marks. I guess it will be out with the micrometer also.

All the best

Berni

[Donels]

The caps are matched to the rods via machining. They are machined together as one component, hence the variations allowed by the machining tolerances means they must be kept together.

You could assemble them the carefully measure to get the same dimensions on all four, ie top to bottom of the bearing hole and side to side to ensure there is no step.

[Craven]

Alignment roll pins should provide a match.

rods1.jpg (35.99 KiB) Viewed 734 times

[avro]

When the original etched Identification number on each conrod is not clear or missing l find that checking the machined chamfer at the edge of the bearing face on each side of the conrod can be a good start to match the cap to the correct rod. The width of chamfer can vary from rod to rod in each set so when the wrong cap is fitted you can often clearly see the mismatch at the join.

Nick

[berni29]

Hi Guys

Just to update and draw a line under this I managed to pair the caps up using machining marks and other cues as suggested. Two were easy, one required closer scrutiny, and the last had only a few matching cues, but it was enough.

Thank you again

Berni

[ceejay]

And then even though you may have a matched set of rods and caps, number each rod and cap, then take them to an engine shop and have them resized and diamond honed to the correct ID size. Then you will know that the rods and bearings will be a perfect fit.