Could this be a reason for wrist pin bearing failure?

[45u]

look back on the boards about 4 or 5 years - you'll see much more of this discussion back then before the shorter small end bearings started to go away - some folks even tried nylon spacers, but they melted - bearings in most kits got much longer after those days

In my opinion they are still WAY to short. Now my RC engines are only up to 32cc but they turn well over 12k plus RPM and I have never had a wrist pin bearing go bad.

 

[Deleted member 12676]

with the assembly in hand just move the rod so that it is centered and then you will see that no matter how much you move the bearing that there will always be bearing rollers betwwen the full width of the rod and the wrist pin.

 

[skyash]

45u has your Bearings ever gone bad be for. I have never had it happen plenty of crank one gone bad and if you like what's wrong with steel washers thay stop the shaft movein in my 4 stroke transfer box haven't worn out in 1000km just an idea what about 2 skateboard bearings put next to each other or one fat one abec 7 should fly

 

[45u]

45u has your Bearings ever gone bad be for. I have never had it happen plenty of crank one gone bad and if you like what's wrong with steel washers thay stop the shaft movein in my 4 stroke transfer box haven't worn out in 1000km just an idea what about 2 skateboard bearings put next to each other or one fat one abec 7 should fly

Thanks for the reply you are the first I have read about the big end bearing going bad I am sure others have as well but not like the wrist pin bearings that many talk about. What brand and type of oil are you using?

 

[skyash]

castrol active 2t for motorbikes .i only get chepo motors and most of them have bad scratching noise in the bottom end and it wears in or away but like 3 got worse then loss of power open it up and burn marks on the crank Wait normally left side i wood say the load side out of 10 motors i have never had a wrist pin go bad some bikes go through 2 stets of rings till it just works with out bracken them eny more. but more bottom end problems then eny thing vibrates on some revs pretty bad lot of kids hav stuff come loose and bad noise on certain parts of the cranks rotation like its not balanced or the bearings worn or loose
scratching noise
scratching noise

 

[aceofspades]

Makes sense.
I wouldn't particularly want to add extra mass of steel to the piston since I already need to find someone with a drill press to lighten the wrist pin for me (or let me use his drill press).
If someone were to produce a set of washers to fit and they were fairly light would certainly be interested in acquiring a set.

So how about green loctite?

 

[FurryOnTheInside]

So how about green loctite?

To prevent the bearing wandering around? Im not certain which one is green now. But my main worry would be that it would be permanent and stop the wrist pin ever being removed.. Unless heat plus a lot of vibrations would be enough to break it up. But then it wouldn't do any good.

For myself, I think I will have to try to not worry, and just rely on the bottom end bearing to keep the con rod upright all on its own. Hopefully moderate compression and good ignition timing will be enough to protect the bearings.

 

[Rob H]

I would think a little more weight would be better than a wrist pin bearing going bad as when they do it really messes up the inside of the motor. I am going to drill my pistons and wrist pin. I just wonder how hard the wrist pin is and good chance will need a cobalt or harder bit.
If will be a while but I am making plains and try to make some wrist pin washers. My lath with are at my friend’s house taken apart and need to get them here at the house and set up.

 

[Rob H]

Wrist pins are chrome moly and case hardened the will drill easily but they are brittle they are more likely to crack than get tore up

 

[Steve Best]

Wow, excellent find, I didn't notice that much "walk" on the rod bearing.
Jag is right, the crank should center the rod, but you are right Jeff, the rod bearing will walk out of the rod.

Steve