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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Ar1100s on November 03, 2022, 12:46:48 AM
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New issue with my 1985 K100.
When I push the starter button then engine cranks, almost starts, but is stopped by a loud clank as if the engine and gears have engaged. I don’t know where to start on this issue?
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Verify the cable connections at the battery are clean and tight; verify that the battery ground connection at the transmission is clean and tight. Verify that your starter cable connections are clean and tight. Verify that the two bolts at the rear of the starter are fastened securely.
How's that for a start? :laughing4-giggles:
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It's hard to identify the problem from what you tell us. The clank makes me think there is a mechanical problem in the engine or transmission. It's possible that there is a problem in the valves or the output shaft. It's also possible that ignition timing, the sprag or the alternator drive could be causing the problem.
Some questions:
Was the bike running properly and then suddenly this problem started?
Were you using the bike regularly or has it been idle for a long time?
Were you doing any work on the bike prior to this problem occurring?
Is the battery fully charged?
What happens when you try to start the engine with the clutch pulled in?
With the bike on the center stand and the transmission in neutral is it easy to spin the rear tire?
Still on the center stand, with the transmission in 5th and all the spark plugs out, can you turn the rear wheel and the engine through several rotations of the crankshaft?
With the spark plugs still out and the transmission in neutral, does the starter spin the engine freely?
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Hard to tell what you mean by 'clank' -- if it's anything like this it was my starter relay.
https://www.youtube.com/watch?v=HmQQ7NBBKlc
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Thank you all for your help. I have trouble shooted with your suggestions and questions in mind! I have come to the conclusion that I need to pull the tranny to see if there is a loose bolt or broken part lurking around.
I’ll let you know what I find!
Thanks
Andy
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Is it in gear when this happens? (with the clutch pulled in obviously)
Does it behave differently if in neutral with the clutch released?
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It is in neutral and happens with or without the clutch pushed in, with both stands up. It sounds as if something metal stops the engine when starting. That is the clanking I’m hearing. I actually road the bike home when this first started with no problem. I put the bike in 3rd then rocked back and forth and the engine and shifting ran smoothly. Once I wanted to restart the bike once I got home, the problem began again. So I need open up the case to see what’s going. Can you link me to a video or instructions on removing and disassembly, and assembly of the transmission within this forum please.
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If the transmission worked fine when you rode it home then my GUESS would be something in the starter circuitry, starter motor or starter sprag. If the rear wheel spins easily with the clutch pulled in or in N then the transmission shouldn't stop stop the engine from starting.
Wouldn't hurt to try this before pulling the bike apart:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/startkillrehab/startkillrehab.htm
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So I need open up the case to see what’s going. Can you link me to a video or instructions on removing and disassembly, and assembly of the transmission within this forum please.
Complete instructions for removal, disassembly, reassembly and installation of the transmission are available in the BMW K75/K100 2 valve Repair Manual downloadable from the Service Manual section of this site (https://www.motobrick.com/index.php?topic=11014.0). Ignore Occam's Razor; simplicity is over-rated. :laughing4-giggles:
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Gee, I would have really liked to see the answers to my questions. I still have no idea of what the actual nature of the problem is.
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Gee, I would have really liked to see the answers to my questions. I still have no idea of what the actual nature of the problem is.
Acute idiopathic starter clanking, aka startus interruptus.
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Got this PM this morning with answers to questions above.
Was the bike running properly and then suddenly this problem started?
Yes. Ran an errand, came back out the engine began to start then stopped abruptly with a clank.
So you were using the bike recently before the problem surfaced.
Were you using the bike regularly or has it been idle for a long time?
I have been bringing it back to life after an accident in 2017.
So the bike has been sitting idle for 5 years. Were you using it much since it started working again?
Were you doing any work on the bike prior to this problem occurring?
Just completed installing a new fuel regulator as well as refurbished injectors and checking all fluids.
Shouldn't have any bearing on the problem.
Is the battery fully charged?
Battery is fully charged.
What happens when you try to start the engine with the clutch pulled in?
Same thing happens.
This is interesting. It tells me that the problem shouldn't be downstream of the clutch if the clutch is working properly, but the following answer contradicts this.
With the bike on the center stand and the transmission in neutral is it easy to spin the rear tire?
No, rear wheel seems to be locked but in neutral. I put it in 3rd gear then roll backwards . It will unlock but do the same thing when trying to start again.
If the clutch is working properly, this tells me that the problem is in the transmission. Along with the previous answer it says the clutch may be malfunctioning along with the transmission
Still on the center stand, with the transmission in 5th and all the spark plugs out, can you turn the rear wheel and the engine through several rotations of the crankshaft?
Haven’t tried yet.
This should identify whether or not the problem is in the engine. Unfortunately, the clutch confuses whatever result comes of it.
With the spark plugs still out and the transmission in neutral, does the starter spin the engine freely?
Haven’t tried yet
This should confirm if the problem is or isn't in the engine, but again, with the clutch suspect the results will be inconclusive.
Bottom line is that it appears to me that the clutch isn't working properly. I'm still unsure how it can be causing the clank. Could be that it is coming apart, but the transmission will need to be pulled to know for sure. I'm also curious about the details of the accident mentioned above. Was it a collision or a drop? Was the bike moving at speed and suddenly stopped? How fast was it moving? Did it stop suddenly? Some accidents can put huge strains on the drive train. Was this one of them?
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Just me but if it's a transmission issue then I'd just swap in a used transmission vs trying to tear the old transmission apart and repair it. I took that approach when I stripped the splines on one of my first K75s.
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Have you replaced the clutch previously?
Not sure if I understand this right. In neutral it moves freely then comes to a stop, then moves freely in the opposite direction until it comes to a stop again. Is that about it?
When turned anticlockwise until stopped, and with the tyre marked at the 12 o'clock position, how far will it turn before it stops, maybe the 3 o'clock position? that might be about one turn of the clutch (with the clutch cover plate or bolt hitting the gear box) Then I thinks you're on the right track and need to look at the clutch.
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Ar1100s, when you are asked questions in a thread like this, please answer them in the thread and not by personal message. That will help everybody know what's going on if your personal message receiver doesn't choose to act as your receptionist or media spokesperson.
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A simple course of action somewhat more effective than rumination would be to remove the rear drive and swing arm to determine if the driveshaft u-joint or assembly is faulty. That should only take an hour or two.
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A simple course of action somewhat more effective than rumination would be to remove the rear drive and swing arm to determine if the driveshaft u-joint or assembly is faulty. That should only take an hour or two.
And if you've never done this before it's a good idea to use a zip-tie to keep the clutch arm from deflecting too much. Otherwise the $48 rubber clutch boot can tear because it has a pretty strong spring behind it.
(https://i.imgur.com/Usk1KSZ.jpg)
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I'm assuming that with the clutch pulled in, the rear wheel turns without locking.
This is unlikely but a quick thing to check, you might have a hydraulic lock problem at cylinder four (or one of the others) Remove the vacuum hose from throttle body four, to look for signs of fuel seeping from the hose into the cylinder.
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And if you've never done this before it's a good idea to use a zip-tie to keep the clutch arm from deflecting too much. Otherwise the $48 rubber clutch boot can tear because if has a pretty strong spring behind it.
Just experienced that the hard way. :( :nono2: Next time I remove the transmission (hopefully never) I was planning on removing the clamp that holds the boot onto the transmission but possibly this is a better plan -- keep the clutch actuator arm in position the whole time. That's why I come to this forum -- to learn better way of doing things!
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I have tried to replicate the problem and have been unable to when starting. I also had fuel spilling all over the place which I think was being caused by by contacts on the fuel relay . I cleaned all that up and the fuel pump no longer runs continuously.
I took the bike on the street and the bike acted as if the clutch was very lightly engaged and not able to move the bike.
I’m guessing my next move is to remove the rear and check the clutch?
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I’m guessing my next move is to remove the rear and check the clutch?
That has been recommended already but on your way in, you need to verify that the driveshaft has been attached to the transmission output shaft correctly and its universal joint is ok. It's unclear to me if you've disassembled down to the clutch previously. For those who haven't, a lift like in the video is unnecessary but being able to do a seated meditation pose while working is helpful. :laughing4-giggles: Regardless, anchoring the rear part of the frame on a sawhorse will make the whole procedure possible. There are posts on the Web showing this method, like the posts in this thread (https://www.k100-forum.com/t15360-clutch-spline-engine-support#179141).
Here's the video.
https://www.youtube.com/watch?v=YCnQE4vQTcs (https://www.youtube.com/watch?v=YCnQE4vQTcs)
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(https://i.imgur.com/eY6UdvZ.jpg)