85 Big Red crank groove.

[3wheeledfanatic]

I picked up a BR that was locked up thinking no big deal. Well it turned out to be a frozen wrist pin, which took a wrist pin puller and a lot of patience to get out. My question is this. The crank journal where the wrist pin goes has a groove, and a very small chunk missing. The new wrist pin goes in tight and doesnt have play, I just dont know what the groove will do Anyone got advice?? I will add that The BR is not perfect and i just want it to beat around on this winter and in the mud.

[Dirtcrasher]

Thats not good, but may work perfectly fine. Up to you if you want to risk a jug, head with valves and a crank.....

[DohcBikes]

The crank journal where the wrist pin goes? Huh?

Anyway, I think you mean the small end of the connecting rod.

Not just lubrication, but actual oil pressure is a key factor to reciprocating components in an engine. All of the components are fitted to clearances that allow pressure to build, creating an oil barrier between the parts. When a bearing is grooved, the oil will tend to lose pressure in that area, sometimes allowing the film of oil that is protecting one part from the other to thin down and eventually get too thin to protect the parts.

In other words, the groove could be the very reason your wrist pin was frozen. Fix it right or eventually it will suffer another failure.

[Dirtcrasher]

Isn't the wrist pin just a oil splash as well as the top of the connecting rod??

Anyhow, I find ignoring even ONE part destroys the top end.

When I was 16, I bought a 87 200X and the guy ran it low on oil, everything was scored/overheated/ruined.

I just bought a new piston/ROCKER ARMS and gaskets but 2 months later i COULD hear the cam and timing chain and sold it for 700$.....

[6speedthumper]

Can you get a picture of what you are talking about? The wristpin goes through one side of the piston, through the small end of the connection rod, and into the other side of the piston. But, you said crank, which has a crank pin the rod and it's bearing pivots on, and it joins the two crank webs together to form the crankshaft assembly. That crank pin is press fit into each crank web. The holes in the webs that the crank pin is pressed into are often called bores, or sometimes, journals. Just want to be clear as to what it is exactly you are talking about. Although, like DC and DOHC, I think you are talking about the rod/piston/wristpin as well.

If it's the piston's wristpin, it is a floating design and is held in the piston with the use of circlips. The wristpin is splash lubricated by direct contact with the splashed oil, and there should be a chamfered hole in the small end of the rod where the wristpin goes through. The pin should feel tight to the touch, meaning the clearance between the wristpin and the bore it goes through in the rod (and the bores in the piston for the matter) is only a few thousandths of an inch, and if all is within spec, you'd be hard pressed to really feel any play in it by hand. Additionally, the wristpin should be able to slid through the bores in the piston and the rod end with minimal effort since it is a floating pin design.

Now, there are press fit wristpins that don't use/require circlips to keep them from walking out of the piston. Basically, the pin is an interference fit by getting pressed tight into either the piston bores and it pivots in the rod end's bore. But, that's another discussion, but, leads me to this; if it was indeed the piston's wristpin that was frozen, and that is what kept the engine from rotating, it'd have to have been frozen in both the piston's bores, and the bore of the rod end it goes through. If it was only frozen in one of the components (piston or rod) it would/should pivot freely in the other component, and the engine should still turn over (essentially it'd be like having a press fit piston pin). If the wristpin was frozen in both the rod and piston you may want to look into that engine further to determine why. Did the engine sit? Was it ran low on oil? Was the oil changed only a handful of times in it's life? Is there any other visible damage to the engine? Or, did someone screw up if/when they rebuilt the top end?

I know you said you just wanted to use it to beat around on, but, if it were me, I'd be making sure that everything was in top shape.

[DohcBikes]

Isn't the wrist pin just a oil splash as well as the top of the connecting rod??

Anyhow, I find ignoring even ONE part destroys the top end.

When I was 16, I bought a 87 200X and the guy ran it low on oil, everything was scored/overheated/ruined.

I just bought a new piston/ROCKER ARMS and gaskets but 2 months later i COULD hear the cam and timing chain and sold it for 700$.....Yes it is and the clearances and movement creates the pressure that determines the thickness of the oil film. Any continuous groove through a bearing surface is going to lessen that thickness and improve the chances for metal to metal contact.