BMW K bikes (Bricks)

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MEMcKay

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Hello, first time posting in the forum. I recently purchased a 1987 K100 RT with 29,000 miles on it. I went through the fluids on the bike because it had sat for a couple of years before I got it. Once back together, I've been using it to commute to work each day - mainly highway riding. The bike makes a pretty good rattling sound at 2000 to 2300 rpm as i accelerate through the gears. I have tried to eliminate usual rattling sources (bike stand, fairing, and the like). It sounds like a timing chain rattle in a car. Is this a possibility with the K bikes. Thanks for the help!

    

blaKey

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Have a look at this post...http://k100rt.aforumfree.com/engine-and-transmission-f10/new-sound-coming-from-timing-chain-area-t708.htm?highlight=timing+chain. It may help.

You mentioned a "pretty good rattling sound". Have you checked the exhaust sheild nuts for tightness?
The "engine knocking sound" might be something to do with the octane rating of the fuel you use?

Just a couple of suggestions.


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K-BIKE

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Excellent suggestions by Ned tracing down a noise can be challenging. 29,000 if genuine is early for wear of the cam chain, I say if genuine because a lot of K's had their instrument clusters replaced due to water ingress. So possibly worth a look at the timing chain after eliminating the other simple ones suggested above. What does the bike look like wear wise does it look almost new which wear wise at 29,000 it would.
Regards,
K-BIKE

    

Ned

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hmmm, 2000-2300 is narrow band which makes me think that it may be related to a resonance frequency. Now that is a bit low for the classic 3500-4000 buzz we usually get due to tuning issues.

If I may use the "H" word example... the Goldwing rattles like crazy at idle due to primary chain slap, but the thing goes smooth and quite above 1200 rpm. Your example is not that. The 2000-2300 is narrow and frequency specific. I don't think that the chain is a problem here.

Can you reproduce the noise in neutral? If so, can you use a large screwdriver or a doweling stick as a stethoscope and go around the motor to see if you can isolate the location. That may help pinpoint the cause.


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Ned

05/1986 (K55) K100RS Motorsport (Europe), Production Code: 0503, 110k km, VIN:0140519 (SOLD)
1976 Honda Goldwing GL1000 (naked)
1997 BMW K1200RS red, VIN: WB10544A1VZA22667
    

Crazy Frog

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Does your engine rattle/knock when in neutral?
Another possibility is a noise or vibration coming from the alternator.
The alternator is attached directly to the engine (alternator bolted to the aluminum of the engine case without any rubber mounts). If the bearings are bad or the rubber bumpers on the coupling are broken , the noise can travel on the engine case. It can be very difficult to locate the origin. This also fit the description of a resonance frequency that Ned is talking about.
I may repeat myself, but I saw this problem of more than 1 K bike. Just remove the alternator and run the bike for 5 or 10 min to see if that solve your problem.

CF


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 Engine knocking sounds between 2000 - 2300 rpm, any help would be great!  Frog15 Engine knocking sounds between 2000 - 2300 rpm, any help would be great!  Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

MEMcKay

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Thanks for the info. I'll get a chance to do some investigative work this weekend. As for the actual mileage on this k-bike, I purchased from the original owners widow. The poor guy passed away this past December. She claimed the mileage to be genuine, wear and tear on the brake pedal, rotors, and loss of finish on lower engine parts look comparable to the miles. The bike has some sun damage on the upper painted surfaces which I think came from where the bike was stored (covered patio). I can't say the mileage is spot on, but I'd guess it was close. Thanks!

    

K-BIKE

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That's good to know and the provenance is excellent, so that said I tend not to think the chain is rattling unless the hydraulic tensioner is not working. Bert's idea is really worth checking and relatively easy.
Regards,
K-BIKE

    

177in70s

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126,000 mi on my 85 K100RS and it had noisy knocking, esp in first 5 minutes and under 3000 RPM. Did many things then measured and found that 7 of 8 valves were tight, exhausts were .003 to .007 " when spec is .010 to .012". Yes, I'm not proud of this but getting them adjusted has made a huge improvement in many areas, a big one is that bad engine sounds in first 5 minutes of ride, below 3000 RPM are gone.

    

Ajays

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To find where exactly the knocking is we used to use a long screwdriver with your ear on the handle, then go to different areas. Chain slap should be easy to define.
Looking on the dark side, having been standing for a long period can damage the cylinder thin coating. The top of the horizontal cylinder being dry. I hope not but it has been known.
Ajays


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 Engine knocking sounds between 2000 - 2300 rpm, any help would be great!  Th_Kengine_gif

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