Main Bearing Replacement

[JERSEYMAN]

Hello All,

I am in the process of replacing the main bearings in an SD as the top bearing has excessive play.

I have no problem in machining a new set of bearings from what I have been told should be PS2 phosphor bronze,

The question I have is on the final reaming of the bearings to get the correct clearance,

What is the reamer size?
Does the reamer have to be long enough to ream both bearings together?
I have an adjustable reamer of roughly the correct size, would this work?
Does anyone have a photo of the correct factory reamer?

Any tips or advise would really be appreciated, Thank You

[Oyster 49]

Rene, I think john at SOS has the correct reamer, Charles will also know. They do have to be line reamed for a decent fit.

[JERSEYMAN]

Here is the type of reamer I intend to use, has anyone any tips on the best way to ream Seagull main bearings?

Also is it worth doweling the crank cases so that it all goes back correctly and not just rely on the crank to centralise the cases, I have no doubt that when tightening the casing bolts the main bearings would be loaded unevenly,

Or am I just complicating things, I spent many years building race motors where balance and alignment are paramount.

I guess after all, A Seagull motor is just a Seagull motor.

[Charles uk]

Sorry about the delay Rene.
Here's a picture of 2 main bearing reamers, the top one is a Seagull original custom made for them & the other is a extra long series one, I had ground to perform the same task as the Seagull one was a bit tired.

If you zoom in on them you can see that the Seagull one is adjustable, & that mine mimics the original in that the first 85mm has been ground down so it slides without cutting, through both bearings before the correct sized cutting portion starts it's job, ensuring that both bearings are perfectly in line.

[JERSEYMAN]

Thanks Charles for the photo, I was curious on how the factory did it.
It looks like my reamer will do as the cone end slides up the reamer to keep it true but I will have to do one end then the other.
I will post some photos when I get round to it.

Thanks

[Stelios_Rjk]

Hi guys,

Why should be PS2 phosphor bronze used? I have found some alloys (phosphor bronze) that seems to be recommended for bearings. PS2 is the only appropriate type or other types can be used?

I have found these phosphor bronze alloys locally. HB is the hardness. The last alloy has the same hardness as PS2 and the previous one has far more bigger hardness than PS2. It is recommended to form bearings in extreme machines/applications (according to the supplier).

[JERSEYMAN]

Sorry, I made a big mistake, the bearing material needed is Phosphor Bronze PB2 not PS2

http://www.tatasteelnz.com/downloads/Br ... Bronze.pdf

My Apology,

Rene