Pitted Tappet Cam Follower

[oldbiker80]

While changing the push rod seals on my recently acquired 1972 R75/5, I found one of the cam followers was badly pitted. I will replace it. Does anyone know if the pitting is caused by defective metal or just damage from wear? The other three followers were fine.

[schrader7032]

Just curious...what oil are you using? It could be that that one follower was not fully treated on that end, but that's hard to tell. Hopefully your filter has sucked up all those bits to keep the engine clean.

[srankin]

What does your cam surfaces look like?

Damage like this can be from running with no oil, wrong oil, extreme wear, improperly tempered parts, or rust from high moisture and sitting.

If it is only one side, I would lean toward an improperly tempered lifter.

How much history do you know about the bike's past? Good luck the damage is just one lifter. St.

[oldbiker80]

Based on the limited history available to me, this was a one owner motorcycle that was stored in a semi-heated garage from 1989 until 2024 when it was purchased by the individual who sold it to me. The second owner did some cosmetic work, changed all the fluids, cleaned and coated the gas tank, cleaned the carbs and rode the bike for about 100 miles before he sold it to me. There was an obvious oil leak determined to be from the push rod seals. While replacing the seals is when I found the pitted cam follower. It was reported that the original owner did maintain the bike well so I have to assume he changed the oil regularly. Not sure if sitting for 35 years would cause pitting in just one cam follower. I suspect the follower was defective when manufactured and just went unnoticed by the two previous owners. I don’t know enough to determine if a pitted cam follower would be noticed while riding. Maybe someone on this forum can better address the cause and effect.

[srankin]

Given the information you have, I also suspect a bad lifter from the factory. As far as knowing about it LOL, really you wouldn't until it did some real damage. The clue to damage would be that particular valve NOT staying in adjustment for the normal adjustment interval. I would think it would start getting noisy as it went out of adjustment due to wear.

Valve adjustment should stay in adjustment for at least 15,000 miles. Adjusting sooner than that could mean a problem.

I guess now, that you have found it, it would be a good idea to look at the cam to see if it did any damage. Most likely due to regular oil changes and good oil, it may be fine. The previous owner did himself a favor by regular oil changes.

The weeping from the push rod seals shouldn't cause enough loss of oil to be a problem, unless you were finding a puddle under the bike after riding.

An interesting find, good luck on the fix, let us know how it worked out. St.

[schrader7032]

I don't have specific information, but I rather doubt that BMW let bad parts go out the door. Just my opinion.

In my mind, ZDDP provides a cushioning effect during the rotation of engine parts. Clearly oil's job is to keep metal parts from touching other metal parts. Oil works great due to viscosity characteristics so that parts moving relative to each other don't touch...oil being incompressible. But there are two points in an engine rotation where the moving parts come to a standstill. This happens when the piston reverses direction at the top and bottom. So with no relative movement, the oil can migrate away from the surfaces, resulting in metal contact. ZDDP was used to actually coat the surfaces and stay in place long enough to keep the metal pieces part until movement returned and oil was flowing back to the various parts.

ZDDP was found to potentially clog up catalytic converters so it was eventually phased out. No older motorcycles run on 0w20 oil which is more common to late model vehicles. But there is still 10w40 and 20w50 running around and since that is not used in vehicles with catalytic converters, they still use levels of ZDDP for older vehicles.

Over 10 years ago, I sent off around 20 oils to be tested for various chemical features...one was for ZDDP. I published that in the March 2013 BMW MOA Owners News. There were petroleum based and synthetic oils as well as some blended products. The general consensus is that about 2000 parts per million combined in ZDDP is the target. More is not necessarily better and lower amounts also is not good. Attached is that plot. At the time BMW's oil was being provided by Spectro but has since changed. A commonly available oil is Valvoline VR1 which has a decent blend of ZDDP.

[srankin]

I agree using proper oil with the additive is the only way to go, that along with regular oil changes.

I find it curious that only one tappet is bad out of four. Now if all four were bad I would say the oil was wrong or something.

I still would like to know what shape the cam lobe is in?

Very curious and interesting. St.

[oldbiker80]

While waiting (six days now) on the USPS for delivery of the new cam follower, I did a visual on the involved cam lobe. There was what appeared to be a single small but shallow scratch on the lobe surface. No other anomalies were observed. I suspect oil protected the cam lobe from the pitted follower. And the pitting was due to a defect in the metal at the time of manufacture.

[srankin]

I guess a person could say that is the sign of a good lubricating oil. The cam was not destroyed. St.