how can you tell when connectings rods need to be replaced

[Beean123]

Hello people, would someone tell me if there is a way to check the hole where the rist
pin goes through the connecting rod, can i mic them, or do they need to be replaced once they show alittle bare metal? thank you

 

[pa23driver]

i've heard the best way to check is to first measure the wrist pin to see if it is in spec, then try and wiggle the wrist pin once its inserted into the small end of the rod (well lubed) if there doesn't seem to be any play and there is no pitting or visible excessive wear you should be good to go.

 

[Punkskalar]

I build about 15 cranks a month. The copper colored coating needs to be consistent on the little end. Some wear is normal, but if it is all gone, its time for new rods. If you see more Chrome/Silver than copper, you need some new rods...

PS, MIC them and you'll get extremely frustrated Even brand new ones aren't always round...

 

[Beean123]

thank you for the reply, i just went and tried there seems to be just a very little wiggle
to them. would it be better to get new wrist pins ? i really dont want to spend the money
and spilt the cases

 

[Punkskalar]

thank you for the reply, i just went and tried there seems to be just a very little wiggle
to them. would it be better to get new wrist pins ? i really dont want to spend the money
and spilt the cases

The wrist pins very rarely have any wear. They are harder than the rod end coating, so they won't wear like the rods will. Do it right the first time, and have no worries... Splitting the cases isn't hard or that costly, but the rods are gonna run you a few bucks of course...

 

[Beean123]

there doesnt look like alot of metal showing but i can see some breaking through the copper

 

[Beean123]

yeah, i heard that, i have pricing them out, thank you for your info

 

[Punkskalar]

A good cheap way to get around it, if you still have 75% or more copper, you are probably just fine. They are going to have wear no matter what, but I have uses rods in 75% or less copper showing before and got another 7-10K out of them. It all just depends on the life span you are hoping for with this engine.

 

[Beean123]

well, to be honest i havent had a bike in a long time, with the gas prices way up there here in michigan, i bought this 79 xs 650, a very nice bike for its age, it had a blown head gasket, i have had the jugs honed,new rings,head work and then i noticed the one rod has some shiny look to it, also new cam chain and guides. if i do the rods, then i would also need the bearings,etc. looks about 300 to 400 more that hurts

 

[Punkskalar]

You'd be surprised how tough those bottom end bearings are. My customers reuse them very often. It takes ALOT of abuse, lack of oiling, rust, etc.. in your cases to actually harm one one of those bearings.

 

[650Skull]

you don't hear of the con-rods breaking very often but it does happen.

 

[xjwmx]

Hello people, would someone tell me if there is a way to check the hole where the rist
pin goes through the connecting rod, can i mic them, or do they need to be replaced once they show alittle bare metal? thank you

The factory manual only says assemble the piston, rod, and pin, with oil on them. If there's any detectable wiggle, then replace the part(s) it takes to eliminate it.

 

[Beean123]

dam, i dont need that happening, so i will be replacing them thank you for everyones help
so the crank is a two piece, so i guess i will find a shop that has the press to pull the crank apart.

 

[Punkskalar]

dam, i dont need that happening, so i will be replacing them thank you for everyones help
so the crank is a two piece, so i guess i will find a shop that has the press to pull the crank apart.

Crank is 4 pieces, and very critical you get it trued back up properly after putting in new rods...

 

[Beean123]

you say the crank is four pieces? i thought it was only 2, ok, i got it, if i take the crank to a shop, they will be able to tell me what i will need, right? I guess i will start calling around and find out what the charges are for pulling the crank apart for me, Thanks for your help

 

[Punkskalar]

 

[Beean123]

Dam,allllrighty then, wow, im not sure if im ready for this

 

[XSLeo]

It's not a difficult process to take a crank apart and reassemble with good parts, trueing it up is the hard part.
I have done two cranks, one stock, one rephase.

 

[cowboy3669]

you don't hear of the con-rods breaking very often but it does happen.

look like one of my engines

 

[duluthmuffler]

How about at crank end? I'm in a rebuilding stage, and I notice that when I move one of the connecting rods side to side (perpendicular to the way they're supposed to move) I get some free play... My manual says 2mm or less is okay. Am I understanding that right? Its okay for a connecting rod to have play on the crank end? Where/How do I measure for the 2mm. The other worrisome thing is that the one rod seems to have more play than the other. Perhaps I'm not understanding things correctly.