rattle at idle (1995 K75 low-seat model)

[64AxeMan]

Yesterday (6/30/2018), on the way back from 20 mile ride in the June NC heat, I noticed a new noise when I stopped at a traffic light.  It was a knock or rattle I'd never heard before.  I've had this bike a little over a year and it has 49,267 miles on the clock.  I started the bike this morning to see if the noise occurs when the engine is cold.  The noise began as soon as I started the engine and let it idle.  The noise occurs at a regular interval...with clutch in or out and whether or not in gear. 

Here is a link to a short youtube video: 

Any ideas?

Thanks,
Mike in NC

Info from VIN search:
Chassis number   0135550
Vehicle code   0571
Series   K569
Model   K 75 85 (0562 ( 0571) )
Body type   0571)
Catalog model   USA
Production date   1994 / 10
Engine   K 75 85 (0562
Transmission   
Steering   
Catalyzer   NONE

[wally.fisher]

What's the idle speed?

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[64AxeMan]

Approx 400 rpm on tach.  When I rev to 1000 rpm, the noise is still there and increases with idle speed but is less noticeable.

[64AxeMan]

So johnny.....not to flog a dead mule....but.....yours makes the same intermittent jack-hammer noise at idle?

[wally.fisher]

It should idle at 950-1050 rpm. Set it up to that and then let's hear it.

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[Laitch]

So johnny.....not to flog a dead mule....but.....yours makes the same intermittent jack-hammer noise at idle?

Mine doesn't make that noise because the idle is set correctly. The idle is too low. Raise the idle, as wally has indicated.  If you don't know how, ask here.

[rbm]

Raise the idle as others have pointed out.  Also, perform a throttle body synchronisation.  Your low idle could be because of maladjustment in the TBs.

[64AxeMan]

Thanks to all.  The bike has idled low since I bought it.  I have never adjusted the idle on a K bike, so I could definitely use some how-to guidance.

[The Mighty Gryphon]

The rattle is in the drive for the balancer shaft.  There is a slot and dog arrangement where the designers left about .030" of slop.  On my K75's the rattle starts just above 1100 rpm and continues until about 2000 rpm. 

I have had some success with cleaning the face of the clutch hub and torquing the clutch nut to the maximum end of the torque spec.  Ultimately though, it will loosen and the clank will return.

There is a thread here someplace(calling Laitch) where I describe what I found and includes a couple photos of the slot and dog arrangement.

When I inspected mine, there were no signs of wear or damage to the parts, so I'm inclined to believe the noise is strictly aesthetic and poses no danger to the engine.

Unless you really want to go into the clutch and the engine output connection I would suggest you get the valves adjusted so the gaps are as even as possible and balance the throttle bodies at least once a year.  Even with that done you might want to get earplugs and learn to ignore the clanking.

[rbm]

Thanks to all.  The bike has idled low since I bought it.  I have never adjusted the idle on a K bike, so I could definitely use some how-to guidance.

See the attachment.  It's a collection of a bunch of articles on the subject which I've collected over the years.  BTW, check your valve clearances first before diving into syncing the TBs.  It's a waste of time to just do the sync procedure and hope for the best.  Isn't this fun; it just gets deeper and deeper. :)

[Laitch]

There is a thread here someplace(calling Laitch) where I describe what I found and includes a couple photos of the slot and dog arrangement.

Here's the thread to which Gryph refers. 

You could raise the idle right now using one partial turn of a screw, but it would be better for you to stop and do a proper tune up—verify a clean air filter, verify correct spark plug gaps, verify correct valve clearances then balance the throttle bodies and set the idle. You've been taxing the engine by running it in its present state of tune.

 Gather the necessary tools and set aside an afternoon. As they say in the ads for term life insurance, you'll be glad you did—although I guess in that case, it's the beneficiaries who are more glad. :giggles

You can sort out the balancer shaft's relationship with the rest of creation after that, if you still think it's important.

[64AxeMan]

Thanks for the input, guys. 

[64AxeMan]

Mystery solved.  Could use a tip on where to find a new scrotator drive cup.....keyword being "economical".  :)

[Laitch]

Mystery solved.  Could use a tip on where to find a new scrotator drive cup.....keyword being "economical".  :)

It isn't usually a part that is separated for sale on the used market. You just need to diligently hunt eBay and used part dealers like TD, Highland Motorsports and others. A new one at MaxBMW is around $55 plus shipping.  It is the same part number for K100, K75 and the late model K100RS so don't limit your search just to K1100 parts.

Thanks for the photo. That explains what happened and helps inform. Was the cup loose?

[64AxeMan]

No, the cup isn't loose.  Looks like the nutz deteriorated.  What's the trick to getting the cup off?  It looks like the only way to safely stop the shaft from spinning is to insert something into the end of the shaft (where it's splined)....but then I can't get a socket on it.  Is there a simple method/solution that I'm missing?

[Laitch]

No, the cup isn't loose.  Looks like the nutz deteriorated.  What's the trick to getting the cup off?  s there a simple method/solution that I'm missing?

I haven't done this procedure, but looking at the workshop manual instructions, the cup is held in position on the shaft by a woodruff key. Keeping the cup stationary—using a strap wrench maybe—then unscrewing the nut would be what i'd try. How's that seem? Somebody will come along to straighten us out if we're going astray. :giggles

[64AxeMan]

Strap wrench is an interesting idea.  Wish I had one on-hand.  I'm not as worried about getting the old cup off since it's damaged.  I'm more concerned with getting the new one torqued tight enough without fubar'n the works.   :dunno2:

[Martin]

+1 Good quality strap wrench, the strap can break on the cheap ones.

Regards Martin.

[Laitch]

I'm more concerned with getting the new one torqued tight enough without fubar'n the works. 

You don't get around to removing the damaged one, you can eliminate wishing and worrying in one go.  :giggles  Keep the fan from moving then if the strap wrench is too exotic. 

[rbm]

I remember having to buy a 12mm triple-square internal wrench to hold the shaft stationary.  But I think a strap wrench will do to hold the cup.  In that case, I'd suggest using an air-driven impact gun to quickly spin off the nut.

[64AxeMan]

UPDATE:  The strap wrench was not able to do the trick (possibly operator error or working by myself).  It took a 14" pipe wrench to hold the cup in conjunction with a 5' pole (from swimming pool) to torque my socket handle.  Once the cup was loose, I had to stick something in the innards to keep the shaft from spinning (risky).  I was expecting a Woodruff key between shaft and cup, but there wasn't one. 

The new cup and monkey nutz arrive tomorrow.  That will be another adventure getting enough torque on the nut to secure the cup sufficiently.  Will probably make a tool shopping trip to get that 12mm internal wrench!

[Martin]

It sounds like it was tightened by a gorilla. If you find anything else overtightened you might want to invest in an impact rattle gun. You can get a 110V 1/2" from $50.00 US a battery 1/2" from $100.00 US or an air 1/2" $90.00 US. They can be a very handy addition when used correctly to loosen stubborn fittings. They can also be a pain in the bum when used to overtighten fittings. Which is normally done by the previous owner and you're the one who wears it. :hehehe
Regards Martin.

[wally.fisher]

There are two almost square cut outs 180 deg opposite around the circumference of the cup.


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[BryanD]

I have a set of through-hole ratchets that work well by inserting a longer extension through the hole with the torx socket inside.

Here is a picture..

[rbm]

But what about the 3/8" or 1/2" drive square.  It's solid.  Do these through-hole ratchets also have special through-hole sockets and extensions?  If so, are they strong?