HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
thumper_calgary

piston pin wear and Conn rod oil ports

8 posts in this topic

when I disassembled by 03 WR engine to do the valves everything was well in spec. However I noticed some pitting on the piston pin and I was thinking it could be starved for oil. has anyone ever tried expanding the oil ports in the top of the connecting rod? I was thinking this would give more lubrication. Now, I'm not about to take a grinder to it, I was just wondering if this is a known issue with other bikes as the rest of the engine was well in spec so I was suprised to find an issue at all. especially there.... I mic'd it and it's in spec. No play in the conn rod so I'm hoping to just repalce the pin and I thought I would just check to see if there was a known soloution. It's sort of hard to see on the phoots but the wear is happening only in the area under the left conn rod oil port. weird

 

IMG_20150218_213308_zpszvaet0aa.jpg

 

IMG_20150218_213132_zpsoytqdxq7.jpg

Edited by thumper_calgary

Share this post


Link to post
Share on other sites

That doesn't look good.  If it were mine, I'd seriously consider replacing it.  If I felt like chancing it, I'd try to see if polishing the connecting rod cleaned it up. 

Share this post


Link to post
Share on other sites

You cannot change the oil passage design, as it will change the oil PRESSURE as well, which you surely do not want to reduce.

 

Clean oil, good oil, and OEM parts last a long, long time.

 

If you let oil deteriorate, it stops lubricating.

 

 

 

Your top and bottom end are shot.

Share this post


Link to post
Share on other sites

I don't think the oil is under pressure at that point in the circuit. Is it not "splashed" up from below to lubricate the piston pin? Yes I will replace the piston pin but the top end looks fine. Ring gap, cross hatching etc looks fine. There's one mushroomed valve. How do you figure the bottom end is shot if only only side of the piston pin is worn like that? It looks like poor lubrication in one specific area to me, possibly resulting from a design issue. Can you elaborate?

Thanks for the responses!

Share this post


Link to post
Share on other sites

I can't see reaming out that hole causing any PSI change either, but the picture of where the wrist pin goes looks like half machined surface vs half worn surface.  My concern would be that additional wear could lead to catastrophic failure.  If that were mine, I would change the rod or crank out.  Since you should change out main bearings when taking apart a bottom end, his comment that the bottom is shot makes sense.  You may just slap another wrist pin and piston in there and you may get another 200+ hours out of it, but who really knows?

Share this post


Link to post
Share on other sites

the oil being in shear at that point will create it's own oil pressure, which can be a tremendous amount actually, if the speeds are high and flow is adequate. google hydrodynamic journal bearing.

Share this post


Link to post
Share on other sites

the oil being in shear at that point will create it's own oil pressure, which can be a tremendous amount actually, if the speeds are high and flow is adequate. google hydrodynamic journal bearing.

Awesome. Thanks I will. Would it be correct to say then that the oil would not reach shear point under the port on the connecting rod? From what I can tell and what I learned from the previous owner this is the first time the engine has been torn down.

Share this post


Link to post
Share on other sites

I'm not sure what you mean by shear point, but the dynamics of the oil flow and pressure are very complicated.  There is basically no force being provided by the open port, but there are boundary effect, momentum, flow direction, etc that will have an effect on what the oil is doing in and around the port.  And with splash feed, it's probably not a very consistent feed of oil, most of which is probably coming from the oil control ring feeding oil onto the pin.  With that theory, I would guess the port is actually the oil return, not the oil feed and that enlarging it would have a deleterious effect on oil pressure.  

 

I wish Grayracer would chime in here...

 

But I agree with Krannie, your rod and wrist pin at very least are trash.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0