Valve clearance

[SamR1200rt]

.

[Boxflyer]

I would say that if it's outside the specification, it should be adjusted...if it's at the limit of the spec, and you are already replacing some of the shims to replace the one that's at 0.23mm as well.
If money was not a factor, I'd put all of the clearances at 1/3 of the range of tolerances.
So for the INT, I'd shoot for 0.16mm and for the EXH I'd want 0.33mm.

Once the BMW Boxer engines started controlling the pounding on the valve components by having dual overhead cams and followers directly on the lobes of the cams, the wear patterns have pretty much always been to slightly increase clearances over the miles. In other words, the valve face and seats don't pound out and cause the valve clearance to get tighter, and what little wear that there is, happens on the oiled components of the valve tip, valve shim, 2 faces of the follower, and the cam lobe.

If the cost of new semisphirical shims is a factor, or they are too hard to find, then if it's in the range of acceptable tolerance, leave it alone.

Brad

[David.]

The shims are available in increments of 0.05mm. Using the next size up shim will put those out of spec. or on the limit clearances in the midrange.

In 47,500 miles, I've only changed one shim on my 2012 Camhead. This was at 10,000 miles when an exhaust clearance was at 0.40mm. Changing this shim put it in the midrange at 0.35mm.

[Boxflyer]

I would change 5 of the 8 shims.
Both of the 0.41mm clearance EXH. valves would be set to a good value of 0.36mm.
The other EXH now at 0.38mm would be at 0.33mm, making it nearer to the tighter end of the range.
Of course the 0.23mm INT would be at 0.18mm, a reasonable number closer to the middle and the 0.20mm set to 0.15mm would probably mean that the valve shims would never need to be adjusted for the life of the bike, plus it might be a little quieter running.

It’s been my experience that the biggest improvement in performance is to check and reset Cam Timing. This CAN make a noticeable difference on the CamHead, as well as the WetHead/ShiftHead bikes.

[Randyjaco]

Ooh, I like that tool Boxflyer. I bought the factory tool, but I sure would have made one like that, if the dimensions had been available last year.

[MarkW]

It’s been my experience that the biggest improvement in performance is to check and reset Cam Timing. This CAN make a noticeable difference on the CamHead, as well as the WetHead/ShiftHead bikes.

Would love to know more about this process - wasn't aware that such a thing was even possible.

[Boxflyer]

The procedure for doing the Cam Timing on the 1200 CamHead engine is very similar to what I do frequently on the 1200/1250 WetHead/ShiftHead.
You need to set and lock the flywheel/crankshaft at TDC with a specific pin that fits in an open hole on the RH side of the rear of the engine block.
The side you are going to be working on will have the arrows on the ends of the Cams pointing towards each other.
Then you remove the existing Cam Chain Tensioner and install the Cam Chain Tensioner Tool with the proper 15mm Sleeve.
Tighten the CCT Tool until it clicks 3 times as determined by it's internal spring.
Now that the engine and valve train are positioned properly, you attempt to fit the Cam Alignment Jig on the ends of the cams. If the fixture does not slip onto the cams, you loosen the bolts that are binding the cam chain gears to the cams themselves and rotate the cams until the Cam Alignment Jig slips onto the cam flats. Leave the Cam Alignment Jig installed to tighten the Cam Bolts.
Lastly, you retorque the bolts holding the cam chain gears to the camshaft, and you can remove the Cam Alignment Jig and replace the Cam Chain Tensioner.

While the engine is at TDC for that cylinder, it is an appropriate time to check valve clearances and adjust if needed.

Remove the TDC pin, rotate the crankshaft 1 revolution, reinstall the TDC pin and the engine is now at TDC on the other cylinder and repeat the steps from the first side.

[MarkW]

Thanks Boxflyer, that is absolutely fascinating (and a really excellent rundown of the process) - won't be a job ill be doing anytime soon though given the special tools needed. When I did my valve clearances recently I used a steel rule against the flats of the camshaft where the index marks are to ascertain TDC. They didn't quite line up perfectly but were damn closen - maybe a degree or so off. How far out do they have to be before I need to worry about getting them reset?

[Boxflyer]

With the range being 0.10mm for both the Intake and Exhaust, and the hemispherical shims only available in 0.05mm spacing...that means that only 1 size shim will put in the range...a second incremental step in shims will put you outside the acceptable area the other way.
Hope that makes sense and answers your question.

[Stu]

@Boxflyer I think he means the cams being out of alignment before causing an issue

[Randyjaco]

The procedure for doing the Cam Timing on the 1200 CamHead engine is very similar to what I do frequently on the 1200/1250 WetHead/ShiftHead.
You need to set and lock the flywheel/crankshaft at TDC with a specific pin that fits in an open hole on the RH side of the rear of the engine block.
The side you are going to be working on will have the arrows on the ends of the Cams pointing towards each other.
Then you remove the existing Cam Chain Tensioner and install the Cam Chain Tensioner Tool with the proper 15mm Sleeve.
Tighten the CCT Tool until it clicks 3 times as determined by it's internal spring.
Now that the engine and valve train are positioned properly, you attempt to fit the Cam Alignment Jig on the ends of the cams. If the fixture does not slip onto the cams, you loosen the bolts that are binding the cam chain gears to the cams themselves and rotate the cams until the Cam Alignment Jig slips onto the cam flats. Leave the Cam Alignment Jig installed to tighten the Cam Bolts.
Lastly, you retorque the bolts holding the cam chain gears to the camshaft, and you can remove the Cam Alignment Jig and replace the Cam Chain Tensioner.

While the engine is at TDC for that cylinder, it is an appropriate time to check valve clearances and adjust if needed.

Remove the TDC pin, rotate the crankshaft 1 revolution, reinstall the TDC pin and the engine is now at TDC on the other cylinder and repeat the steps from the first side.

I was surprised to find that the valve timing on my 17RT was 10-20 degrees out. It evidently came that way from the factory, because it had less than 4K miles on it at the time. Cam alignment is definitely worth checking.