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Discussion Starter · #1 ·
Today I dug out my old cam chain from my 2009 K13S. I laid it up along a new chain, setting up one leg of the loop against the chain and one leg. Careful alignment with straight edge and on a smooth steel plate, both at the same temperature. Comparing 28 links along the two legs next to each other I found the old chain was 1.4mm longer measuring at link pins. So this makes the old chain over all, total length of the loop a little over 2.8mm longer than a new chain. I can see this will make some difference in timing. The old chain has 75,000 miles on it. I have these new parts on hand as I'm going to do a valve clearance check and install a new chain at 130,000 miles on my 09 K bike. Might be a little early but I'm having some idle problems and want to get everything to base line. It wants to idle at about 1050 rpm and hunts a bit there. I can also hear and feel what seems to be chain snatch while idling. I did not think there was much stretch when I removed this chain a few years back but have now changed my mind.
 

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2012 BMW K1300S (also 1993 BMW R1100RS and 1974 BMW R60/6)
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I did not think there was much stretch when I removed this chain a few years back but have now changed my mind.
Over time I've noticed a lot more noise on my 2012 K13S 77k miles at cold startup when the cam chain tensioner isn't pressurized. I replaced the tensioner piston assembly hoping that would cure it but it didn't. Your post makes me suspect the longer chain rattles a lot more until the tensioner has oil pressure.

How much of a chore is it to replace the cam chain?
 

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Discussion Starter · #3 ·
You also need to change the driven sprocket on the exhaust cam. It is a lot of work, but not as much as doing a valve check. Need to lock the bike at TDC, remove side case cover, loosen up the tensioner, remove driven sprocket making records of the TDC mesh markings as you need to rotate the cam some to get both bolts out of the sprocket. Remove chain, replace chain snug up new sprocket, etc. You get the drift.
 
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I'm curious, have you thrown a degree wheel on one to see how much retarded that amount of stretch makes the cam?
 

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Hey Beech, did you inspect the gears and confirm the wear they display is equivalent to the chain? Just curious if the gears might wear considerably slower than the chain stretch due to them being harder material?
 

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I agree Fastdaddy. Chains and sprockets should last a lot longer than130k km. I tend to think that the chains are the weak point and that initially just a new chain would suffice. Not 100% positive though
 

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The problem with the silent link chains (one problem anyway) is that the nature of the individual link plate contact with the sprocket teeth creates a wear pattern unique to that particular chain. The new chain, while close, will never quite match that wear pattern and wear will be accelerated. True in automotive applications as well as motorcycle.
It's also a very heavy chain design and that weight being slung out away from the sprockets is part of what contributes to the stretch problem.
That's why most performance applications will either use gears (not applicable on OHC applications) or double roller designs.
 

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‘That's why most performance applications will either use gears (not applicable on OHC applications)….’
Really 😁

Bicycle part Motor vehicle Rim Automotive design Automotive tire

Desmodici RR

Who could afford that!
 

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How about "not normally" applicable for OHC applications or unless you "have really deep pockets".
I had a 1997 Honda VFR750 with a V4 engine with gear drive cams. Cost me $9200 out the door. And that engine was an evolution from when it was introduced in 1990.
 

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$15,500 in today's dollars.
Which is $3400 less than the $18,900 I paid for my K1300S in December of 2014. So still a bargain, especially when compared to the price of the Ducati with the same engine configuration. And that VFR750 engine was an anvil for reliability. I put about 114,000 miles on it and only ever changed oil, filter and plugs. Check the valve clearances, but never had to adjust any.
 

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Discussion Starter · #14 ·
Cool stuff above. No, I did not do the degree wheel. I suspect some math and using the driven gear diameter it could be calculated. I agree that a new gear is needed even if wear is not visible to the eye. I decided that yesterday and ordered one last night. Unfortunately my model K13S does not have a removable drive gear, nor is one sold.
 

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So it’s a lifetime gear. When it’s worn out the lifetime is over. I bet it’s just an interference press fit and could be removed with some heat and a puller. Unfortunately I don’t have the equipment to cut a new gear and heat treat it.
 

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Discussion Starter · #16 ·
So I had my friend a mechanical engineer with a PE do the math for me and the one side of the chain 1.4mm longer changes the cam shaft angle 2.6 degrees. Which is significant.
 

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Significant? Sorta/kinda... Not uncommon in the hot rodding world to move the cam timing back and forth much as 4 degrees or so. But if it doesn't NEED to be moved well then. Long as within limits it just moves the torque curve up or down a little.
The table below (credit Summit Racing) gives a good overview.
How does it affect performance?
Advancing or retarding the cam will move the Torque curve higher or lower in the rpm range.
AdvanceRetard
General EffectImproves low-end power and throttle responseImproves power at higher rpm's
Intake Valve Opening EventHappens soonerHappens later
Piston to Valve ClearanceDecreases intake valve clearanceIncreases intake valve clearance
Moving 4° Causes...Peak torque about 200 rpm soonerPeak torque about 200 rpm later
 

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The real problem would seem to be the link chain stretching enough to ride up on the crank sprocket and grenade things.
For the life of me I can't understand why BMW did away with a replaceable crank sprocket on that engine. Seems like every other engine they produce auto or motorcycle has a replaceable crank sprocket/gear. Odd.
Did forget 1 thing in the whole gear, chain etc. discussion. My ST1100 had a belt! 90k mile service interval or some crazy thing like that.
 

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Discussion Starter · #20 ·
I believe with a longer chain it will be retarded.
 
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