PK Rebuild After Top End Failure

[210061741]

Iv'e been rebuilding a PK-80 that someone sent me.
It was siezed up and wouldn't turn over.

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11211.jpg
http://i887.photobucket.com/albums/ac72/RidingRich/SDC11210.jpg
http://i887.photobucket.com/albums/ac72/RidingRich/SDC11189.jpg


Here's what i found.

A large amount of metal dust behind the clutch and around the countershaft bearing housing.

Take a look.
http://i887.photobucket.com/albums/ac72/RidingRich/SDC11177.jpg

Initially you would expect that the bearing spun in the housing.
In fact it didn't.

All that metal was from the clutch cover.
http://i887.photobucket.com/albums/ac72/RidingRich/CAUSEOFDUST.jpg

The 3 guide pins on the clutch assembly and the star nut were wearing through the clutch cover.

I have noticide this on a few of the PK engines.

After further dissassembly of the engine i could easily determine the real cause of the failure.

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11198.jpg

The wristpin needle bearing was severly damaged.
Several needles were broken to pcs.

You can see the needle fragments and severe damage to the wristpin as well.
Deep gouges around the pin where it broke in half.


http://i887.photobucket.com/albums/ac72/RidingRich/SDC11197.jpg

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11199.jpg

After the needle bearing failed it caused extreme loads on the wristpin and got very hot.

The wristpin was snapped into 2 pcs after the bosses inside the piston fragmented due to the extreme heat.

You can see the fragments from the piston and it is also cracked on both sides from the skirt to the piston dome.

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11200.jpg

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11202.jpg

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11203.jpg

You can see the top of the boss is gone.

http://i887.photobucket.com/albums/ac72/RidingRich/SDC11209.jpg
http://i887.photobucket.com/albums/ac72/RidingRich/SDC11208.jpg

The good thing here is this is all easy to fix.

I have a new piston, Wristpin, And Needle Bearing for this engine.
I will be replacing all the gaskets and seals and also have a set of the Quality 6202 mainbearings. The engine Cases and Crank are in good shape as well as the rest of the engine. The cylinder has 1 minor scratch in it and is still usable.

However i will be replacing the cylinder with a ported cylinder.
I cut the transfer tunnels much larger to help with flow and produce higher power.

The exhaust port it cut a bit larger and the intake is substancially dropped.
http://i887.photobucket.com/albums/ac72/RidingRich/SDC11183.jpg

This engine will soon be going back to it's owner who will be using it with a shift kit and a nexus hub.

Cant wait to see what he gets out of it.


BBBBRRRRRRRRR BBBBRRRRRRRR VVVrrrroooommmmmm

 

[GearNut]

That all is right on par with the common failures I have learned of with most any HT engine.
These things would last sooo much longer if there were initially made with good quality bearings.
I have 2 engines, one used, one brand new, that I plan on cleaning up the ports on before I run them.
Can you or would you sell the quality bearings you use to the common tinkerer so we can upgrade these engines before they fail like that?

 

[210061741]

Yup there all commonly available.

I get them from erie Bearing.

For the bearings in the case...

Mainbearings

F.A.G. 6202.2RSR.C3.J22R Pull the bearing seal on one side for the mainbearings.
The bearing should be open sided inside the crankcase to get oil.

Countershaft.
F.A.G. 6202.2RSR.C3.J22R
Leave both sides sealed.

And for the wristpin bearing
INA Needle roller and cage assemblies K10X14X13-TV

It's pretty common too and cost $5.00. Rated to 29000 rpm

Erie Bearings has them or can get them.
http://www.eriebearings.com/

The 6202 bearings are $10.00 ea.

You cant change the crankshaft big end easily.
It's an odd size

 

[210061741]

Heres a link to the needle bearing data

http://medias.schaeffler.de/medias/hp.ec.br.pr/K*K10X14X13-TV;a2uM-RUEoWU-?clrsb=1

 

[give me vtec]

you're the man rich.

You are pioneering work that people will reference for years. I think this thread should be made into a rebuild sticky others can use in the future.

 

[GearNut]

Thank you VERY much, rich!
This is definitely an upgrade that everyone should do if they can.

 

[210061741]

I have never run an engine out of the box.
I take them all apart.

But yup...Them are good bearings.

I run my little engine to death and haven't had a critical failure yet.

The good thing about putting a sealed bearing on the crankshaft is it keep the spring on the crankcase seals from getting into the bearing.

I have experienced that 1 time.
Destroyed the bearing cage real quick.

 

[Fabian]

Hi Rich,

It's refreshing to see that you've taken good quality, high resolution and in-focus photos.

Nothing is more frustrating than lousy, out of focus photos in this day and age of digital automatic, point and shoot cameras.
It's just not possible to get a bad photo these days with digital cameras, but some people manage to do the impossible.

Regards Fabian

 

[Fabian]

What you can do with the conneting rod big end bearing is to modify the connecting rod by reaming it out to 22mm and driving a high carbon sleeve back in the hole and machining the I.D back to 20mm.

You can then use a high specification caged needle roller bearing of the size: K16 x 20 x10, instead of the standard K16 x 21 x10

or

You can just use a new style crowded roller bearing replacement crankshaft which solves all the previous big end bearing problems.

I've written about my surprisingly simple solution to prevent big end connecting rod failures (the only thing that has ever failed) in all my 5 engines, by a simply jetting the carburettor correctly and using 98 octane fuel and 20:1 fuel/oil ratio.

Fabian

 

[210061741]

Yes you are correct about the bearing Fabian.
But that is beyond the means of the average tinkerer.

If i was going to rebuild the bearing i would use the full complement of rollers. "Cageless"

But it seems that buying a cheap Moped Crank Solves them issues.
Plut then you have something that is properly balanced up to 12000 rpm reliably.

I know you have some pics of what you did with the bearings.
Can you post them for us.

Options are allways good.