Failing rockers

[Borsiin]

I am currently working on a 690cc (102*84,5) single cylinder motorcycle engine. It has a 4valve SOHC rocker arrangement with roller rockers according to pic. And the rocker rollers fail way to often, the bearing needles eats through the surface of the pin and then seizes wrecking rocker and cam. The pic below is from a worn pin before failing.

rocker.PNG

IMG_20190810_000732.jpg

The OEM part is only available as a complete rocker for +200$ and even the updated parts fail way to fast. So I am searching for a company that either sells rollers as a loose part and some input in how to upgrade the pin and bearing to last. Is a higher spec material in the pin going to make it last?

[mag2555]

I can not tell from the photo , but does the roller get sprayed with oil from the main rocker shaft?

It looks like getting oil into the needles and having just flung out is the root of the failure since the roller itself does not fail.

[Borsiin]

I can not tell from the photo , but does the roller get sprayed with oil from the main rocker shaft?

It looks like getting oil into the needles and having just flung out is the root of the failure since the roller itself does not fail.

There is no organized oil spray of the roller from the factory. I have tried drilling a 1.5mm hole in the central portion of the rocker to get a poor mans spray jet onto the roller. In the end I cant say that it lasted longer.

The roller vs cam surface always look fine unless the roller has seized on the axel so I guess that the problem is insufficient oil film in the needle bearing..

Or is the axel to soft compared to the needles? Or is the diameter too small ? Many questions and unknowns....

[englertracing]

Goodridge makes mountain bike brake lines they are 6mm take apart fittings with ss braided teflon hose.
If you could tap an oil passage and run one up to the valve cover you can aim an oil jet at the roller.
You will need a restrictor./jet
I have used this line for just this when modifications to the cylinder made the original head feeds unuseable.

IMAG0856.jpg

See the little line running to the valve cover.
Could be done with hard lines as well.
You could even run something to a block with two oil jets if needed.

Alternately maybe you could dam up the cylinder head and keep the rocker submerged.

[englertracing]

Is it a ktm 690 duke or enduro?
Looks like damming it up wouldnt be that easy
Jawa dams the head for oil level on purpose for spring cooling.

The other thing i was thinking is maybe you can bush the rollers.

[JoePorting]

Is the Piston hitting the valves? Check Piston for valve marks.

[mag2555]

In that case I would made up a steel tube that connects to the oil feed in the head or somewhere .
Route the tube such that it can spray oil right at either side of the roller opposite the rocker shaft , form a spray noslle at its end by crimping the tube and restrict the tube somewhat if need be by closing off the tube with solder and then drilling it open to a size of maybe ,035" for starters.

The more oil pressure the smaller the restriction hole can be , but the hole may need to go to .045" to get the job done if the motor only runs around 35 psi of average oil pressure.

[BobbyB]

Are you using aftermarket cams & springs? If so, you may be overloading the bearings. You should be able to find just the bearings pretty inexpensively. You might be able to replace the bearing for a few dollars,very often, and find that the shafts last many times longer.
The shaft and bearing must have perfect surfaces to live....Very clean oil too.

[Momus]

I'd be checking the hardness and Ra of the failed pins first up.
They should be from 58 to 64 HRC with 62-64 ideal. Ra under .2.
Are the bearings full complement?

[Borsiin]

Is it a ktm 690 duke or enduro?
Looks like damming it up wouldnt be that easy
Jawa dams the head for oil level on purpose for spring cooling.

The other thing i was thinking is maybe you can bush the rollers.

Yes it is the KTM LC4690 08-19 engine. I am replacing about 25 sets of rockers a year for my customers and a few for my own race engines. A bushing would probably take the loads for longer but i guess a busing will need more lubrication.

[Borsiin]

Is the Piston hitting the valves? Check Piston for valve marks.

Nope no contact. This is happening to both dead stock engines used on the street and my highly prepped race engines. But all engines have sufficient clearance valve-piston.

This wear happens on bone stock street used engines after about 20 000km.I have tried several versions in my race engines. Hotter cam with OEM valvetrain gives crappy longivety. When changing to titanium valves, lighter valve springs and titanium retainers together with a even hotter spec cam the life gets a little better. But it is still the first thing on the engine that needs rebuilding.

[Borsiin]

Are you using aftermarket cams & springs? If so, you may be overloading the bearings. You should be able to find just the bearings pretty inexpensively. You might be able to replace the bearing for a few dollars,very often, and find that the shafts last many times longer.
The shaft and bearing must have perfect surfaces to live....Very clean oil too.

Any leads on who sells bearings or where i could buy pin+bearing+outer roller?