2000 K1200RS - Valve Shim Adjustment and Cam Chain Guides

[1wheeldrive]

Hey All,

My (new to me) Y2k K1200RS is getting a thorough going over. I have very limited service records, really just a few documented oil changes in the owners manuals and such, and it has 47k miles on the clock. There is no doubt that some things have been done but undocumented. For instance, the brakeb and clutch fluids aren’t gross. But, since I don’t know what has or hasn’t been done, I’m assuming everything is needed.

Today’s project was the valve clearance check, and unfortunately two of my exhaust valves are tight. Been reading up on the valve adjustment process, which doesn’t seem horrible. I’ve adjusted valves on many other shimmed valve bikes before. The key caviat has always been to assure the chain doesn’t slip a tooth (or more) on the crank sprocket. How does one assure that doesn’t happen if they don’t remove the timing cover?

Which may be somewhat moot, since at 47k miles the timing chain guides should have been replaced, but I have no evidence that they have. So, I’m probably looking at popping the crank and timing covers off, but I’m a bit intimidated by all the crank seal shenanigans. I have both the FSM in pdf and a copy of the Haynes. My questions in this area are: how realistic are the 30k mile requirements for chain guides, and what is all the hoopla about the timing cover seals?

Appreciate any insight you can provide.

Edit - I need to get the new steed out of the garage and into daylight for a photo op, and to update my profile phote!

 

[lee]

The key caviat has always been to assure the chain doesn’t slip a tooth (or more) on the crank sprocket. How does one assure that doesn’t happen if they don’t remove the timing cover?

Zip ties.

K1200RS Valve Adjustment

The BMW K1200RS: Motor Über Alles

 

[1wheeldrive]

Thanks, lee,

I’m well aware of zip tying the cam wheels to maintain timing, but how do you not lose time at the crankshaft (unless you pull off the timing cover)

 

[lee]

how realistic are the 30k mile requirements for chain guides

My wife put 85,000 miles on her K1200RS and I put 89,000 miles on mine.
Never changed the chain guides.

If I remember right the guides are plastic??
Maybe with the age of your bike they may need changing. I don't know.

 

[lee]

Thanks, lee,

I’m well aware of zip tying the cam wheels to maintain timing, but how do you not lose time at the crankshaft (unless you pull off the timing cover)

I don't know.
The one time our bikes needed a shim changed I had the shop do it.
You should get a answer soon. There's a lot of Brick knowledge on this site. @PGlave and @98lee

 

[1wheeldrive]

Good point. You’re saying the plastic guide demise may be more age related than mileage. That is well worth considering.

 

[lee]

Good point. You’re saying the plastic guide demise may be more age related than mileage. That is well worth considering.

Paul or 98Lee can answer that.

 

[98lee]

There's a lot of Brick knowledge on this site. @PGlave and @98lee

Sorry, I try to concentrate on the 2v bricks. I try to keep it simple. Simple bikes for simple minds.

 

[lee]

Sorry, I try to concentrate on the 2v bricks. I try to keep it simple. Simple bikes for simple minds.

Oops, I forgot about the difference between the 2 valve and 4 valve Brick.
Paul may be in the same boat.

 

[GTRider]

Yeah, 2V are shim over bucket design and can change shims without removing the cam(s). 4V are bucket shims and require removing the cam to change a bucket, further complicated by the fact that you can’t determine the new bucket size until the old is removed. But, still not a terribly involved process. As for the guides, I put 100k miles on the OEM guides on my K1200GT and know of others that have gone almost 200k without issue. But, of course, as soon as one mentions that a guide will shatter so there’s that.

The FSM has an illustration that shows the few small points where RTV should be applied- it’s only in the corner or crevice areas and no need to widely slather it on the re-usable valve cover gasket.

Best,
DeVern

 

[1wheeldrive]

My wife put 85,000 miles on her K1200RS and I put 89,000 miles on mine.
Never changed the chain guides.

If I remember right the guides are plastic??
Maybe with the age of your bike they may need changing. I don't know

I actually once owned a 2V. A K100RT, which I did shimming on way back when. No need to pull the camshaft, as I recall, and they did not call for chain guides to be replaced. Hopefully someone with 4 valve brick experience will chime in about the guides and whether replacing them is really required at such short intervals.

 

[1wheeldrive]

Yeah, 2V are shim over bucket design and can change shims without removing the cam(s). 4V are bucket shims and require removing the cam to change a bucket, further complicated by the fact that you can’t determine the new bucket size until the old is removed. But, still not a terribly involved process. As for the guides, I put 100k miles on the OEM guides on my K1200GT and know of others that have gone almost 200k without issue. But, of course, as soon as one mentions that a guide will shatter so there’s that.

The FSM has an illustration that shows the few small points where RTV should be applied- it’s only in the corner or crevice areas and no need to widely slather it on the re-usable valve cover gasket.

Best,
DeVern

By “guides”, I assume that you mean the timing chain guides, right? I already ordered the service set from Max, and they appear to be made of a solid plastic of some type. But if I don’t really need to go into the timing cover, that would be a much easier shimming.

I’ve run a few other (non-BMW) bikes well past 100k miles, and never even considered replacing the chain guides. On the other hand, I’m currently in process of doing a top end job on my son’s old ‘94 XR650L Honda (piston melt down) with only 5k miles, and those chain guides are all cracked. There is a metal backing to the plastic guide on those, but I wouldn’t want to see what loose chunks of the old brittle plastic could do inside the crankcase, so I’m changing $100 of chain guides on that one.

 

[lee]

I actually once owned a 2V. A K100RT, which I did shimming on way back when. No need to pull the camshaft, as I recall

That's correct. On the K75 bikes we had it was easy to change a shim.
On the K1200RS I removed the body work before riding to the shop. Without bothering with the body work, they only charged 1 hour labor for the shim change.
Still more of a hassle compared to the K75 because I had to ride 350 miles.

 

[PGlaves]

I'm a bit late to the table here. I never had a 4 valve brick. But as for the chain guides on Old Smokey they were fine at 380,000 miles when I wrecked the bike.

 

[1wheeldrive]

For whatever reason, BMW specified replacement of certain parts of the timing chain guides at 30k mile intervals.

I already decided to adjust the valve shims that needed it (just two exhausts were tight by .05mm) without removing the timing cover. Mostly because I don’t have the seal tool to reinstall the timing cover yet. Will have to look into how people are doing that.

FWIW - 7 of my exhaust valve buckets were marked 2.70mm, and one was a 2.65mm. I was able to swap the 2.65mm with one of the two tight valves and get that into spec. On the other tight one, I used my drill press and a piece of aluminum rod to sand down the attached shim nub on the underside of the bucket. The top face of the bucket is clearly hardened steel, so it doesn’t wear rubbing against the cam lobes, but the little shim nub on the underside is not.

I cut little patches of 270 grit finishing sandpaper and double-sided taped them on the end of the rod to get down inside the bucket. It took a lot of little pieces of sandpaper but I got the bucket down to 2.64 mm, (using digital inside micrometer to measure) which brought the clearance right in to the lower end of spec (0.25 - 0.30mm). I wouldn’t want to do that for a lot of valves, but for one or two valves it beats waiting for shim buckets from BMW, not to mention the cost of them.

 

[98lee]

For whatever reason, BMW specified replacement of certain parts of the timing chain guides at 30k mile intervals.

I already decided to adjust the valve shims that needed it (just two exhausts were tight by .05mm) without removing the timing cover. Mostly because I don’t have the seal tool to reinstall the timing cover yet. Will have to look into how people are doing that.

FWIW - 7 of my exhaust valve buckets were marked 2.70mm, and one was a 2.65mm. I was able to swap the 2.65mm with one of the two tight valves and get that into spec. On the other tight one, I used my drill press and a piece of aluminum rod to sand down the attached shim nub on the underside of the bucket. The top face of the bucket is clearly hardened steel, so it doesn’t wear rubbing against the cam lobes, but the little shim nub on the underside is not.

I cut little patches of 270 grit finishing sandpaper and double-sided taped them on the end of the rod to get down inside the bucket. It took a lot of little pieces of sandpaper but I got the bucket down to 2.64 mm, (using digital inside micrometer to measure) which brought the clearance right in to the lower end of spec (0.25 - 0.30mm). I wouldn’t want to do that for a lot of valves, but for one or two valves it beats waiting for shim buckets from BMW, not to mention the cost of them.

Whenever adjusting valve lash on exhaust valves on early Kbikes, you should always attempt to aim for the loose limit of spec. But since you are already done, it just means that you will have to readjust that valve sooner.

 

[1wheeldrive]

Whenever adjusting valve lash on exhaust valves on early Kbikes, you should always attempt to aim for the loose limit of spec. But since you are already done, it just means that you will have to readjust that valve sooner.

Understood. However, the clearance spec is only .05mm wide, and shims only come in .05 increments. If you have a valve at the minimum spec limit and put a .05 smaller shim in, that will push it out of spec on the high clearance side. That’s where I prefer to live, since it’s the safer condition. Generally valves get tighter with wear, since the wear occurs on the valve faces and seats, where they are hammering each other at 1/2 whatever rpm you are running at.

That said, I also have to believe that the clearance spec range is selected with that knowledge in mind. Clearly the minimum spec is not the true minimum that the engine will run at. I had two exhausts that were a full .05 BELOW the minimum, and the engine ran fine. The engineers understand the amount of wear that is probable between valve checks. The minimum end if the spec range definitely has some cushion built in.

 

[98lee]

However, the clearance spec is only .05mm wide, and shims only come in .05 increments. If you have a valve at the minimum spec limit and put a .05 smaller shim in, that will push it out of spec on the high clearance side.

You might want to recheck your math. The new shim will put it exactly on the high limit, precisely where it should be set.


1wheeldrive:
That said, I also have to believe that the clearance spec range is selected with that knowledge in mind. Clearly the minimum spec is not the true minimum that the engine will run at. I had two exhausts that were a full .05 BELOW the minimum, and the engine ran fine. The engineers understand the amount of wear that is probable between valve checks. The minimum end if the spec range definitely has some cushion built in.



The spec. is not the minimum that will allow the bike to run. It is the minimum that will allow the bike to run well with minimum negative effects.

Heat is the enemy of valves and seats. Intake valves are cooled by the incoming air fuel mixture while they are open. They generally don’t move much due to this cooling.

Exhaust valves, on the other hand have superheated exhaust gases rushing by while they are open which heats the valve tremendously. The only way the exhaust valves get any cooling is during the time they spend in contact with the seat thereby transferring the heat to the cylinder head and then to the coolant in the head. The shorter the time in contact with the seat, the hotter the exhaust valves run. The lash increases or decreases the duration of the seat time while the bucket is on the heel of the cam lobe. Less lash = less seat time = less exhaust valve cooling = more valve heat = more valve recession = tighter lash = less seat time = less exhaust valve cooling = more valve heat, etc., etc. etc.

That’s why the engineers say when it gets to the low limit of lash, change it to the high limit. They don’t say when it gets to the low limit, keep riding for an indeterminate mileage until you think it is doing sufficient harm to the engine to bring it back into spec.

Think kind of like your engine oil. Your engine will run fine (sort of) two quarts down, but you would be negligent doings so intentionally. It could very well decrease the longevity of your engine.

Letting your exhaust valves tighten below spec. could decrease the longevity of your engine. If your valve is currently at the low limit of spec., how many more miles before it is below the spec. limit? 10,000mi? 5,000mi? 1,000mi? When were you planning to check it next? You know it is at the limit now. You know the correct shim will make it perfect. But, you do you

 

[1wheeldrive]

Ha ha. I like your train of thought.

But there is one minor niggle I have with your theories. The truth is that the engine actually runs the best when the valves have the least possible clearance. This gives you the largest valve lift and longest duration.

The problem, or rather the potential consequence, is that if the clearance is small enough, when the engine heats up, it may not be able to close a valve at all. This should result in loss of compression, but also potentially burnt exhaust valves. I’ve never heard of a piston contacting a valve due to valve adjustment. That’s more of an urban myth than reality.

All of these minor valve clearance issues are now moot on my project bike, as at the end of an otherwise wonderful 200 mile ride yesterday, I was getting clutch slipping if I whacked the throttle too hard. I realize this probably means dropping the entire rear of the bike out and replacing some faulty oil seals. A daunting task at first consideration, but not something I’m incapable of.

I’m getting the full exposure to the K bike’s quirks, rather rapidly now. I’m OK with that. When I bought such an old bike, and for such short money, I knew there would be problems. With 5 other bikes in the garage, it’s not urgent that this one be repaired immediately. It does give a retired guy some things to work on…

 

[98lee]

Ha ha. I like your train of thought.

But there is one minor niggle I have with your theories. The truth is that the engine actually runs the best when the valves have the least possible clearance. This gives you the largest valve lift and longest duration.

The problem, or rather the potential consequence, is that if the clearance is small enough, when the engine heats up, it may not be able to close a valve at all. This should result in loss of compression, but also potentially burnt exhaust valves.

From a short term horsepower view point, you are correct.

From the standpoint of engine longevity, you are incorrect. The extra heat accelerates valve recession. I have seen bikes with only 100,000 miles on the thinnest shim available due to failure to keep the valve lash within the ideal limits. Next stop for them is rebuilding the head. With more and more parts becoming NLA, that could be an expensive proposition. With appropriate maintenance, these bikes would easily double that mileage.

And what causes the burnt valve? Heat! But prior to burning valves, you start getting symptoms like stalling at stop signs from exhaust valves that are as little as .2mm too tight. It’s already doing harm at that point.

But, with todays disposable mind set, who cares? When it fails just toss it and get another one.