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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: hoodun on September 30, 2013, 09:33:44 PM
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M K75 is making a whining noise. Maybe its normal? Its pretty loud. Check out the vid and let me know if yours sounds this way. You can notice it most towards the end. Its a higher pitched noise.
...I've only owned pre 1980s bikes, and its a sound I've never heard before...
BMW K75 (http://www.youtube.com/watch?v=xx4JPMCw7_s#)
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Is the starter still turning?
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Yeah that doesn't sound 'quite' normal, or at least it's much louder than the normal fuel pump whine.
What happens if you hit the indicators, do they work ok? Horn etc?
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Everything works. horn, lights, etc. The starter works fine. The sound seems to be loudest on the right side by the air box. It doesn't sound like it is coming from the starter. Its louder than the engine. Could it be a bearing? A pump? The engine was covered in oil when I got it. Oil was caked on pretty thick.
I do have the monkey nutz thing going on with the alternator. Could it be an alternator bearing? Though it doesnt sound like it is coming from that area.
I may have to borrow my friends stethoscope.
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Further inspection points to the noise coming from the alternator, on top of the rattle noise. Im guessing the alternator bearing is bad.
Or maybe its normal. These bikes appears to make the same noise?? -a little less obnoxious than mine (though mines recorded on my cell phone...):
BMW K75S 1993 (http://www.youtube.com/watch?v=2btMmDPOFLA#)
1994 BMW K75RT Video Over-View (http://www.youtube.com/watch?v=ppNnMjuxaGU#)
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Is the starter still turning?
The starter is turning with the engine running. Is this normal or should it be completely stopped?
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Is the starter still turning?
The starter is turning with the engine running. Is this normal or should it be completely stopped?
No, the starter shouldn't be turning.....
Sounds like the starter sprague clutch assy is sticking with dirt and not free-wheeling like it's supposed to. I'd try some seafoam or other type of some engine detergent additive to clean it. It is lubricated with the engine oil in the intermediate housing.
More often than not, when the starter sprague has problems it's just the opposite and the starter turns but the engine doesn't.....
Here's a couple of links for you to read futher.
1: http://www.motobrick.com/index.php?topic=2547.msg14344#msg14344 (http://www.motobrick.com/index.php?topic=2547.msg14344#msg14344)
Near the bottom of the 1st post is this link for further help.
Starter Sprag Clutch Problems ~ author robert fleischer (http://bmwmotorcycletech.info/kstartersprag.htm)
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I removed the alternator and the monkey nutz are in bad shape. Any chance that this would cause it? Maybe its wishful thinking?
I checked around with a screwdriver at my ear and the sound is definitely coming from around the area where the alternator dog ears are. At least on that corner of the engine area. It sounds like the starter is turning with a screwdriver up to it and my ear. Though, that could be the gears inside that Im hearing. Its hard to tell.
I'm running some sea foam in the engine and will see if that helps. Ordered some new monkey nutz. Fingers crossed.
(http://s19.postimg.org/lgmv841ar/2013_10_02_18_41_30.jpg)
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I don't know why you would go after the monkey nuts when it's already been determined that your starter is turning when your engine is running, poster Scott just above here and I agree that's where you should be looking. Once your engine is started, your starter should be sitting there like dead weight. There's no other option with that.
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I don't know why you would go after the monkey nuts when it's already been determined that your starter is turning when your engine is running, poster Scott just above here and I agree that's where you should be looking. Once your engine is started, your starter should be sitting there like dead weight. There's no other option with that.
Im with you here.
I put in some sea foam as suggested and will see if that fixes the sprag, if the sprag is actually the issue, as Im not entirely certain the starter is actually turning (as described above). Im going to ride it for a few hundred miles with the oil additive and see what happens. I may also try to spray it with carb cleaner while I have the starter hole open. I'm definitely not ripping the bike apart just yet! If I do, the clutch etc. will get done. Something for rainy season.
In the meantime, the monkey nuts, syncing the carbs, and adjusting the valves, etc. are all other things that still need to be done to this newly purchased neglected bike. Its also one less sound (rattling) that I have to listen to. Baby steps.
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Perhaps a garage stethoscope will help you find the source of the sound. Take a 12-24" long piece of copper pipe and hold one end to your ear, touch the other end to different locations on your idling motorcycle. If you have never tried this before you will be surprised at what you hear.
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I have come to accept the whine. The bike starts fine. Runs fine. There is however a rattling noise at around 1400-1800 rpm. I replaced the monkey nutz and it did not go away. I'm not entirely certain I put them in correctly though. I have the connecting rubber piece facing towards the engine. Or maybe I ordered the wrong ones. The sound really seems to be coming from that area.
How should the monkey nuts go in? What else could be the source of the rattling. Possibly the sprag? Which brings us back to the whine... Though the bike starts great and the starter does not seem to be turning. I used a copper pipe and hit the start button while listening then I can REALLY hear it turn. So I do not think the sprag is sticking. Though maybe Im wrong.
I'm hoping that I do not have to rip her apart again, though I will if it comes to that. I just re-lubed the transmission splines and they looked brand new along with the drive gear splines so I know that is not the issue.
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I'm having the same issue with rattling that seems to be coming from the alternator. I suspect one of the sets of monkey nutz aren't seated properly, causing one of the fins on the drive dog and one of the fins in the alternator cup to whack up against each other. I read on another post to use grease to keep the monkey nutz in place while installing.
http://www.k100-forum.com/t5428-after-replacing-starter-motor-brushes-starter-only-spins (http://www.k100-forum.com/t5428-after-replacing-starter-motor-brushes-starter-only-spins)
I didn't do that and was aware that one of the sets of nutz was flopping around and might not sit still during install. I'll try again with a dab of grease in the cup and let you know if the rattle goes away.
Van
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One set of rubbers displaced won't cause a rattle. You only need one set in place to stop the fins contacting each other.
There's really nowhere else for them to go - if they're not in place they'll be sat in the recess under the alternator. If they're slightly displaced then the alternator won't slip into place like it should, you'd have to fight it on.
On mine, the rubbers had completely disintegrated leaving the fins to smash each other to pieces and there was still no discernible rattle.
A rattle from here is more likely to be either a dead/dying bearing or the dog bolt/cup nut loose.
Of course, you could have installed the alternator with the cup misaligned, meaning the fins are all up against each other and the rubbers are doing nothing - imo it still wouldn't rattle though.........
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Very good points, thanks.
I will check the cup bolts. This noise wasn't occurring before I pulled the transmission and clutch pack off and reinstalled. I'll try to do more diagnostics and if I can't localize better where it's coming from with a stethoscope, I'll start a new thread.
Van
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one other little thing - I'm not sure what type of rubber is used, but be a bit thoughtful about the type of grease you use to locate them if you do....
Most rubbers don't like a lot of greases.
I used silicon based 'O'ring lube when I installed mine - was the only way to get them in because they were so tight.
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I think he was referring to using the grease to keep the rubbers from falling out of the cup when trying to put the alt back into place. I've used a small dab of black form-a-gasket to keep them in the cup.
M-hobo, you say you removed the trans and clutch pack, and now have a rattle. I hate to ask, but are you sure you got all the pressure plate bolts tight? They say never to assume, so I thought I better ask......... :dunno
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I think he was referring to using the grease to keep the rubbers from falling out of the cup when trying to put the alt back into place. I've used a small dab of black form-a-gasket to keep them in the cup.
That's what I thought he meant, but my reasoning was better to use 'safe' grease than have some perishing... Plus, the silicone lube is properly sticky. I got mine from an aquatic type shop..
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I think he was referring to using the grease to keep the rubbers from falling out of the cup when trying to put the alt back into place. I've used a small dab of black form-a-gasket to keep them in the cup.
M-hobo, you say you removed the trans and clutch pack, and now have a rattle. I hate to ask, but are you sure you got all the pressure plate bolts tight? They say never to assume, so I thought I better ask......... :dunno
Scott -- I bought all new bolts and torqued them to spec, and got the clutch alignment tool from Ken Lively. I marked up the clutch pack before removing and am pretty sure I got it in the same way it came out...plus the alternator seems to be vibrating in concert with th rattle and the stethoscope tells me the rattle is located there...but I won't know until I pull the alternator...again. Ugh.
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Pulled the alternator, seated the monkey nutz with a dab of black RTV as recommended in the Lieberry post, lined up the marks on the cup with the drive dogs and it slid right in.
No more clackety-clack...
Thanks, folks!
Van