Wrist pin width

[Bowtie316]

I am working on an ESR 330 with wiseco piston, hotrods crank. This is my first big bore motor so bare with me, I searched around but didn't find any help.

The width of the small end of the rod and the wrist pin bearing seem to match up, but the space in the piston seems to leave a large gap. Now I know the rod itself will center up in the piston, but it seems like the bearing could ride to one side or the other and only be about half in the rod. Is this normal or is there a different bearing for big bore pistons?

Didn't take a picture last night and I'm not sure on the gap size, but here is a sketch of what I am trying to describe. [/URL][/IMG]

[Pumashine]

89mm wiseco piston


Width is .945" inside piston


Bearing should be .855" which should leave .050" clearance on each side.

[Bowtie316]

Uh oh. That is nowhere near what mine looks like. I will get a picture tonight as well as measure the rod and bearing width and the piston gap. From what I remember, my rod and bearing look the same but my piston has a much wider spacing.

Thanks again Pumashine.

[Pumashine]

These are wiseco pistons from ESR. The .940"-.945" should be what they measure. I have a stock 68mm piston here and the gap measures 1.065"

[Bowtie316]

These are wiseco pistons from ESR. The .940"-.945" should be what they measure. I have a stock 68mm piston here and the gap measures 1.065"

Well I measured my piston with it still on the rod and close as I can get it measures .950" so it's probably correct. My bearing however measures .775" so that's quite a bit less than what yours measured.  Where should I source the correct bearing for this thing?
[/URL][/IMG]

[udontknowme]

Well I measured my piston with it still on the rod and close as I can get it measures .950" so it's probably correct. My bearing however measures .775" so that's quite a bit less than what yours measured.  Where should I source the correct bearing for this thing?
[/URL][/IMG]

if thats wiseco rod i wish you good luck. they been known to snap in half.

[Bowtie316]

if thats wiseco rod i wish you good luck. they been known to snap in half.

No it's a hotrods crank and rod.

I found a stock Honda bearing I had laying around for another build and it was the correct width.  I stuck it in there, much better now.  Thanks for the help.  

[udontknowme]

not many people know it but theres a similar situation with the cr500 bearings. prox/honda is wider. if i recall the wiseco/hotrods bearing are the same and narrower but have 1 more roller.  personally i only use prox

[Pumashine]

When Nate McCoy built his first Puma they exploded the wrist pin bearing on the Dyno because they had used the standard bearing. There was more clearance machined in for the rod on the piston as the pistons were built for the Polaris. My builder Dave Moore at the time had made 2 small spacers that sat on the wrist pin to keep the rod centered. I used these spacers on my first Puma piston until the correct pistons were made or the new wider wrist pin bearings were available.

You made a good choice by going with the wider bearing. Could have been an accident waiting to happen.

[Bowtie316]

You made a good choice by going with the wider bearing. Could have been an accident waiting to happen.

I agree, I'm a nervous wreck on this motor. I'm glad I popped it open to check it out.  

Thanks for the help and parts Tony, they showed up yesterday and everything looks great.