Mechanical hypercondria and Engine clatter

[Bengt_Phorqs]

Aussie Pete started a thread in the technical articles section and I can't respond there.  Perhaps Rob or Justin could move it to this board.

His concern is about mechanical noise and he can't pinpoint the source.  My first suggestion is to pull out your mechanics stethoscope and see if you can isolate the noise to a particular part of the engine.  Valve recession doesn't seem to be the culprit.  It is backfiring and rattling.  I'm going to make a SWAG here and ask if he has ever de-coked the heads.  Anyone else have any ideas?

[ambrose78]

Hi Bent,

I only realised after posting the post was going into the FAQ section after posting and then it was too late to move/delete the post  .

I set the exhausts to .15mm (6 thou) and left the inlets as they were at 0.1mm (4thou). My bike is running a lot nicer this morning, very smooth idle and easier starting as well  - didn't notice any pops or crackles this morning on the way to work and the clatter seems quieter.

I personally have never decoked the head but will look into it.

[Bob_Roller]

Have you checked the torque of the 6 nuts that hold down the cylinder head/cylinder recently ?

This is a severely wild guess, but I had the needle bearings in the rocker arms start to come out through the gap in the blocks that are at each end of the rocker arms .

The edge of the needle bearing shell cracked out, allowing the needles to escape, but they get cut up if the get in that gap and usually end up in the oil sump .

I had 6 needles missing on one rocker arm .

Like I said, just a wild guess here .

If it happens again, it's a quick check while you're performing a valve clearance check/adjustment .

[Justin B.]

I have moved thread...

[montmil]

I believe the revised and most often quoted valve lash settings are 0.004-intake and 0.008-exhaust. The slightly larger gap on the exhaust valve provides a miniscule amount of additional cooling/heat transfer for the sometimes abused exhaust valve and seat.

Clatter? Just a bit more BMW Music to enjoy.

Monte

[montmil]

... de-coked the heads...

Yo, Bengt. Is this anything like switching to Mountain Dew?
Did y'all have BBQ for Thanksgiving? We included some homemade tamales next to our big bird.

Monte

[Barry]

Do you think I have to worry about the clatter? or should I just tighten up the exhaust clearances a bit (perhaps 6 thou) and keep on riding?

I guess they would clatter at 10 and 12 thou and it sounds like you fixed it but why did they open up?  I can't think of a mechanism.

I'd just ride and check them again pretty soon.

[ambrose78]

Thanks for the replies

certainly is a lot quieter riding with the exhaust gap set smaller.

I'll take a look at the roller bearing next check - which won't be too far away just to see what's happening after a bit more riding.

[nhmaf]

+1 on running the exhaust at .008 = it is possibly slightly noisier but it is really the recommended setting and may give you longer life of your exhaust valves  Changing the valve clearances also mean that one should recheck/balance the carbs, too.

I suspect that the valve lash didn't open up or increase..  it is common for things to turn ever so slightly while people are trying to hold the screwdriver steady while tightening the locknut.   IF you didn't recheck your valve lash clearance after rotating the engine through a cycle the last time you adjusted the valves, try it  - you'll likely find that the .008"  may have ended up as .009" or similar....

[montmil]

...I suspect that the valve lash didn't open up or increase..  it is common for things to turn ever so slightly while people are trying to hold the screwdriver steady while tightening the locknut.   IF you didn't recheck your valve lash clearance after rotating the engine through a cycle the last time you adjusted the valves, try it  - you'll likely find that the .008"  may have ended up as .009" or similar...

Ran the valves on the '81 R65 last Monday. Took me several attempts to do the final "pull" on the lock nut and end up with the correct 0.004 and 0.008. No biggie. Coarse threads, it seems, on the adjuster screw. Had music on the box, warm shop, good job.

Monte