Rod Top Bearing Oil Modification

[dps650rider]

650 Central has a service where they drill holes in the pistons from the oil ring groove to the rod top bearing to improve oiling. I have been running JE 700cc pistons in my bike for years and as far as I knew this modification was already present in the pistons from the factory. Am getting ready to put my top end back together and took a close look at this oil passage. This is of considerable interest because the right top rod bearing in the crank that came out of the bike showed evidence of lack of oil. I did a thorough job of flushing out and blowing out the oil galleys in both directions. When I started the right squirter MAY have been partially plugged, don't know for sure so possibly this was the problem.

Attached are a couple pictures of where this oil passage comes out in the piston. It comes out in the middle of the piston bearing where the rod fits and has a semi circle groove. Seems to me that this doesn't do much to increase oil at the rod top bearing where it is really needed.

Anybody have any thoughts on this?

 

[YamadudeXS650C]

the right top rod bearing in the crank that came out of the bike showed evidence of lack of oil

I am interested in the evidence you have of oil starvation. Got a photo of the small end rod bearings?

 

[dps650rider]

Here you go. This is an aftermarket rod so there is no copper plating. The other rod on the left side is perfect.

 

[YamadudeXS650C]

Here you go. This is an aftermarket rod so there is no copper plating. The other rod on the left side is perfect.

Ah, I see what you're talking about. Thanks.
I was actually hoping that your rod was OEM with the plating, so I could compare it to the small ends in my spare motor that show evidence of oil starvation.

As to your question, there have been threads here about this modification. I'll see if I can find them.....
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[dps650rider]

Pic from a stock engine I had in my bike many years ago. Again the right side had problems and left side is OK. Before I tore it down there was no indication of a problem.

 

[Bewarethemoon]

Ah, I see what you're talking about. Thanks.
I was actually hoping that your rod was OEM with the plating, so I could compare it to the small ends in my spare motor that show evidence of oil starvation.

As to your question, there have been threads here about this modification. I'll see if I can find them.....
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I’d be very interested to read these, I had a brief search the other day but no luck.

Daniel.

 

[YamadudeXS650C]

I’d be very interested to read these, I had a brief search the other day but no luck.

Daniel.

I can't find them either.

 

[dps650rider]

I tried too, no luck.

Thanks for looking.

 

[TwoManyXS1Bs]

A forum search on "piston oiling" gets several threads where we discuss this.
Gotta follow the imbedded links, too.

Studying MMM's piston mod, you can see where his oiling ports exit to the sides of the small-end, allowing oil to enter the conrod's small-end, not the piston's wristpin boss as in dps650rider's pistons...

 

[Bewarethemoon]

A forum search on "piston oiling" gets several threads where we discuss this.
Gotta follow the imbedded links, too...

Brilliant, thanks TwoMany!

That’ll be tonight’s reading.

Daniel

 

[TwoManyXS1Bs]

Daniel, I just updated that post with a pic...