Another engine rattle really bad noise

[Chri5]

Hi
So i was on my way to work pulled out for a slow over take reved up to 3400 ish rev and a horrible noise started so i have put the bike off the road

the engine starts great pulls as normal and idles perfect but im not willing to run high rev with this noise

Ive removed the alternator in the vid ill link in my next post i will be stripping the bike to clutch at the weekend but if any one has any ideas what it might be please shout out

[Chri5]

The noise which sounds like the mic cant handle it is what it sounds like the noise comes in at 2500rpm cold and 3200rpm when warm. The noise increases with revs

[Laitch]

Did the moto accelerate abnormally slowly when you revved it while riding it?

[The Mighty Gryphon]

Output shaft rivets???   They have been known to let go on early model K100 engines.  A lot of owners replace the 6 rivet output shaft with a later model 12 rivet shaft.

[Chri5]

No the bike behaves normally revving and acceleration seem normal

[Chri5]

Yeah output shaft is on my list to inspect ive read the many posts that mention it. am i right in saying its engine out to get to the output shaft

[Chri5]

Is there any way to inspect the output shaft rivets with out removing the engine can they be seen throught the crack cover maybe? Weather permitting i should be crack it open sunday but if i can inspect without taking the brick right back i can order the later shaft and have it ready to go as ill be working out side in rainy old britan and the less time i have it in bits the better

[Laitch]

Is there any way to inspect the output shaft rivets with out removing the engine can they be seen throught the crack cover maybe?

It might be possible. Inspect the attached photo supplied in a comment by Spike Cornelius following John Brown's IBMWR essay about output shaft gear repair with the engine in frame. A small portion of the output gear can be seen just to the left of the arrow. Cornelius's comment also explains how to observe the gear for problems. Brown heard a different noise than you are hearing perhaps because all the gear rivets broke at one time. His moto wouldn't move by engine power after that.

[Chri5]

Thanks Laitch thats a useful article

[Chri5]

So after some poking around under the crack cover all 6 rivets are there and appear in tacked although one seems to be protruding out more than the others maybe by 1mm as the othere 5 are flush with the gear on crank the other thing i found which i think is the reason for noise is i found about 0.5mm or more axial play in cylinder 1 conrod i believe some engines allow a little play in that direction but cylinders 2-4 are rock solid

Does any one know if the brick should be solid or if there is a tolerance of play along the crack *crank *for each conrod

[caveman]

I would pull the cap and inspect bearing and measure the crack crank and connecting rod boar.

[daveson]

With a helper turning the rear road wheel, forward and back, in gear, can you see or feel (if lucky) or produce free play between the output shaft gear and damper housing? If so you probably want wd40 on small external bolts for sump and lower crankcase half.  Especially also the larger internal bolts, I think 4 or 6 from memory. I had to let them soak for a few days before they would turn.

How many km on your bike and do you think they're genuine?

[Laitch]

Does any one know if the brick should be solid or if there is a tolerance of play along the crack for each conrod

That isn't a crack; it's a joint or space. A crack in an engine usually refers to a partial fracture/breakage of a component like a block, cylinder head or pump casing.

The limit for end play of a connecting rod big end bearing is 0.40mm, according to the specs in the BMW K75/K100 2V workshop manual available in Repair Guidance at this site. If end play measures 0.50mm—you're just guessing—that rod bearing in your engine is over the limit. You can measure end play right now using a blade-type feeler gauge. A 0.45mm blade shouldn't fit into that joint. Download the manual and view the engine spec charts in the Engine section. 

Visually check for play in the output gear by movement of the crankshaft. Rivets should be tight.

I'm uncertain we've tracked the source of this noise yet. I think you'll need to start disassembly. Does the oil pressure indicator light up?

Don't take seriously advice when it's offered up from somebody's memory; verify it.

[Chri5]

A quick correction i ment crank not crack my phone auto corrected

So with the feeler guage should that be placed between the conrod adjacent "weights" im not really sure where i would put them

The bike has 50k on which i have no reason to beleive they are not genuine

The noise can be heard on the video as noise descriptions are some what subjective i would describle it as a raspy rattle it sound like the mic on the video is blowing out but its not thats the noise

When rotating the rear wheel the shock absorber housing on the output shaft visually looked solid to the gear the riverts all felt solid to when poked

I will make a vid of the conrod on cylinder 1 and post it

[The Mighty Gryphon]

Just curious, but have you pulled the alternator and checked the monkey knutz, clutch cup and the drive dog?  Worn knutz or a bad bearing or splines on the dog can make quite a racket.  An easy check is to run the engine with the alternator removed.

[Chri5]

Yes Gryph that was my first thought the monkey nuts look new and the bearings are good the noise is persistant without the alternator which is removed in the vid

[Laitch]

So with the feeler guage should that be placed between the conrod adjacent "weights" im not really sure where i would put them . . .

The connecting rod and its bearing shells ride on a rod bearing journal. The counterweights are opposite the rod journal. You're measuring the space between the rod bearing cap and one side of the rod bearing journal. See the attached photo. Download the manual. In fact, it's better to have two or more manuals by different publishers so you can get varying explanations.

[Grant]

Sounds like what I had, it was the no return valve for the gas , located at the bottom left of the gas tank, the ball bearing comes loose inside the valve and rattles a lot. Only happens on early bricks. Put you ear up to gas tank when you rev the engine.

[Chri5]

So ive check the endplay in the conrods and they are all within tolerance although cylinder 1 is greater (<0.3mm) than 2-4 (<0.2mm) im glad about that so im back to output shaft visual inspection even though the riviets all look in place and feel solid in situ im going to have to take it out to have a proper look i let u know what i find but im just not convinced its that is there any other possible culprits it could be Or checks i should undertake before i open the engine up??

[Laitch]

. . .  im just not convinced its that is there any other possible culprits it could be Or checks i should undertake before i open the engine up??

Grant made a suggestion in Post #17. Why don't you acknowledge it and check that valve? It's inside one of the two hose attachment pipes on the left underside of the tank—a spigot usually removable with a wrench. Soak it with penetrant first to help with loosening it.

[Chri5]

Yeah the noise is from by the crank towards the alternator area

The disc are old but the noise occurs when stationary the engine is only a baby with 50k on it

[daveson]

If it's that high we can eliminate the sump area. Look for any worn bearing or loosness on the gearbox side of the intermediate housing (bellhousing thingo between gearbox and engine) hopefully like the alternator drive. Then I spose remove gearbox,  hopefully something lose in clutch, or anything on the gearbox side. If still no luck,  looks like the intermediate housing has to come off and hope for a worn bearing on the engine side of the intermediate housing.

[Laitch]

Just curious, but have you pulled the alternator and checked the monkey knutz, clutch cup and the drive dog?  Worn knutz or a bad bearing or splines on the dog can make quite a racket. 

Yes Gryph that was my first thought the monkey nuts look new and the bearings are good the noise is persistant without the alternator which is removed in the vid

I think you've missed some of Gryph's advice, Chri5.

Gryph indicates the driving dog should be inspected but you didn't mention inspecting it. You indicated that the drive cushions and bearing looked good to you. It's possible the screw that holds the driving dog to its shaft loosened, the screw stripped, the splines within the dog might be damaged or a combination those conditions. The noise could be from the shaft riding over the dog's splines. The arrow on the attached diagram indicates the driving dog; the photo is a view from the engine side of the dog showing the splines within it. You had better pull the alternator again so you can reach in and check that dog for looseness.

The photo and diagram are from the MAX BMW parts fiche.

[billday]

Have you checked for trombones?

[daveson]

Good one billday!

Also,  check the voltage across the battery for irregularity while noisy. 

Does the noise change after pulling in the clutch?