R75/6 Tappet - Lifter Noise

[sblaylock]

I'm working on an R75/6 and have significant noise coming from, what seems to be, the tappet on the LH side. I checked the valve clearances and they are good. I did need to make a small adjustment, but the noise was there before and after.

I took a long screwdriver and placed it on the case near the tappet and placed the other end in my ear - yes, handle end to ear, and it's definitely coming from near the push rod seals. Placing the screwdriver on the head or valve cover and listening there seems to be quiet. I can't tell 100% if it's the intake or exhaust side as it's pretty loud fore and aft. I've also had a couple of other people listen and they agree it's from the lower end.

Could this be and issue where the tappet has cracked i.e. the old style angled window type? Were they in the R75/6 or had BMW changed them to the straight window type in the /6. If not a cracked tappet any ideas on what it could be?

Cam seal is not leaking - surprisingly, but if there was something going on with the cam I would think it would be both sides.

The bike has ~45,000 miles on it and is ridden fairly regularly in the summer. I've done a full fluid change and there was nothing out of the ordinary in the engine oil. The bike came into my shop after a 1000+ mile trip around Alberta and BC with both fork seals blown out. The woman that owns the bike said they had been on some rough dirt roads on the trip, but I can't see washboard and potholes causing this type of issue.

Anyways, any help would be appreciated,
Scott.

[schrader7032]

My /7 had the straight windows when I did the top end. My '69 R69S had the angled lifters. So somewhere in between, they changed. I can't imagine what could be loose to make that kind of noise. If the lifter had collapsed, you'd seen an issue with valve clearances. But a crack in the lifter could make the noise. I don't know how else to diagnose it but to pull the cylinder and then extract the lifters.

[sblaylock]

Hi Kurt,

That was what I was thinking too - pull the jug and see what's going on, but I was hoping someone may have an idea before I started to pull it apart.

I'll give it a couple of days to see if anyone else chimes in. If not, I'll head down that path.

Thanks,
Scott.

[schrader7032]

You seem to isolated the noise to the lower end. I just remembered that sometimes there can be some noises if the head gasket it put on wrong. This results in the pushrod rubbing on the side of the gasket as it sticks out into the tube the pushrod runs in. But you're nearer the base, so likely can't be that. Maybe before pulling everything off, just pull the pushrods on one side and roll them on a flat surface to make sure they're straight...and look for any markings along the length.

[sblaylock]

Hi Kurt,

Good idea on checking the pushrods to see if one, or both, are bent.

I'm assuming if the gasket was up against the pushrod I'd be able to see it protruding in with the pushrods removed. I'll have a check for that as well.

Thanks again for the help,
Scott.

[sblaylock]

Hi Kurt,

I checked the pushrods in a set of "V" blocks and a dial indicator and they were straight. Looking down the pushrod tubes everything looks good, insofar as there is nothing protruding into the tubes that would rub on the pushrods. I was able to apply a slight lateral pressure on the pushrod after seating it in the tappet and was able to confirm both tappets slide smoothly with no noticeable catching. So mystery not solved... yet.

Before pulling the rockers I checked the valve clearances and they were perfect.

I buttoned it all up and will take it out for a spin tomorrow once the rain stops.

Scott.