Wrist Pin Bearing

[widebear]

Originally Posted by Eric K

Consider that the primary load on the bearings is due to the compression and combustion. The bearings are loaded the same when the engine fires. The rod bearing has much more surface area to distribute the load. The wrist pin bearing is proportionally higher stressed with the same load.

I concur.Extensive testing by Husky ,re; oil ratios, revealed that the most severly effected component by using lean oil/fuel ratios was the top end bearing. Since I only run @100-1. I replace the $12.00 bearing every top end service. I realize that this topic is'nt about oil ratios but as Eric pointed out that little bearing does take alot more abuse than people might at first think.

[Trailrider]

I have been riding for 40 years, replacing the wrist pin bearing, along with the wrist pin, clips, rings and gaskets was always done when the top end was serviced. The possible damage from not doing so is not worth risking the small savings. Racing highly strung 100cc aircooled MX bikes in the early 70's
probably had something to do with it.
Trailrider

[GMP]

The pin is replaced because it comes with the piston. Sometimes I'll replace the bearing, sometimes not. Yes, its cheap, but depends on if I have one or can get one when I want it. I never seem to notice any wear, but I run 36:1. The point is the rod is just as prone to wear as the bearing and pin, and you don't replace that until a total lower end rebuild. If the pin and top end bearing are obviously worn for whatever reason, it seems like you would be kidding yourself to ignore the rod.

Do you replace a hooked countershaft sprocket and keep the trashed chain?

[Ud_luz]

Originally Posted by widebear

Since I only run @100-1.

What bike do you have? That's even leaner than I run my trials bike.

[noobi]

Originally Posted by Ud_luz

What bike do you have? That's even leaner than I run my trials bike.

i think you mean that 100:1 is richer. rich and lean is refering to the volume of fuel not oil. so 32:1 or 40:1 i leaner than 100:1

at least i think thats what its refering too...


i get what GMP is trying to say, in that why replace the wrist pin bearing if you dont do the rest of the bearings, in the same way that you dont replace one wheel bearing if its worn out.

but i also get the hassle that you have to go to in order to get to the bottom end bearings.
i think most people just see that its there and its easy to change so they just do. i did

[GMP]

What I'm saying is the wrist pin, bearing, and rod surfaces should all wear together. Its not a big deal either way. Who has had a failure? No one I know, and its cheap even if it makes no difference.

[widebear]

Originally Posted by Ud_luz

What bike do you have? That's even leaner than I run my trials bike.

97,99.01 kx 250's and all four of my gasgas two strokes 01x2, 02 200, 03 mc 250. No problems ever and they are all jetted very, very krisp!