R90s rapping sound

[Bamboo812]

It's possible for the rockers to be mounted too low causing the push rods to contact the push rod tubes lower edge. Watch the push rod as you rotate the engine, you'll notice that it moves up and down in the tube as well as in and out. I had this happen after using a c-clamp to hold the rocker block end play while torquing the heads.

[Duane Ausherman]

bamboo is right. Once the end blocks are pinched together (by any method) it is important that the pushrod is properly positioned in the pushrod tube.

One can see evidence on a pushrod if it has been hitting. They hit just where the head meets the cylinder, or at least that is what we found.

[KNS]

Does anybody know where I can buy replacement needle bearings? They are Dorkopp 310-3640 but seem to be very difficult to find, the local BMW dealer says he can order them in but they are $40.00 CDN each making $160.00 plus tax per side ouch! I was hoping to see if I could get them from SKF or the likes. Any ideas? My bike was built 1/75 according to the number plate on the steering column. I gather there might be different bearings depending on what month of 75 the bikes were built.

[tsa]

. . . I have noticed is that the push rods are scored fairly heavily around the push rods which indicates to me that they are rotating in the tubes and not aligned in the center of the cam follower. Could that be my noise?

When getting to know my R80, under the rocker covers, I noticed that someone had put on one cylinder head gasket the wrong way (they are not symmetrical), so that the pushrods on that side rubbed against them. Result: clear localised scoring all around them at the gasket level. No unusual sound from that, though.

[Duane Ausherman]

We saw that wear from the incorrect installation of the head gasket from time to time. That metal in the gasket can do a lot of wearing on the push rod.

[moosehead]

Does anybody know where I can buy replacement needle bearings? They are Dorkopp 310-3640 but seem to be very difficult to find, the local BMW dealer says he can order them in but they are $40.00 CDN each making $160.00 plus tax per side ouch! I was hoping to see if I could get them from SKF or the likes. Any ideas? My bike was built 1/75 according to the number plate on the steering column. I gather there might be different bearings depending on what month of 75 the bikes were built.

Got mine from Motobins...complete needle bearing was 9£ (About $16 CDN) per bearing...

http://www.motobins.co.uk

Motobins part # 08760

Find them under "engine parts / rocker arms / miscellaneous rocker arm parts " or just do search of Motobins part #.

[KNS]

Well I finally got enough time from work and installed the needle bearings yesterday and that seems to have been the problem and I guess also why I thought it was feeling underpowered. Unfortunately it is raining here today so I have not had a chance to go for a spin. Thanks to all I never would have thought of the rocker arms.