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Discussion Starter #1
I'm still working on the valve adjustment on my 05 LT. It all sounds so simple when you read the instructions, but then things never seem to go as easy when you get working on it. To start with, I'm having trouble moving the chain tensioner down so I can lock it out of the way. I though I had it down when I took the cams off the first time, but soon found out I didn't after I got the cam gears off. It doesn't seem to want to move very freely, even though I've rotated the rear wheel to maybe pump oil out of it. I did get it to move a couple times, and was able to get the gears back on and everything back together, but I might have to take it all apart again, as I'm not sure if I have the right clearances on the buckets. That brings me to the other issue I'm having with this procedure. I'm rotating the rear wheel until the cam lobes for the valves I want to check are pointing away from the valves as the procedure I'm following states I need to do. However, it does not say exactly where these lobes need to be to get the right measurement. The procedure I'm using http://www.gunsmoke.com/motorcycling/k1200rs/valves/index.html says it is not that critical exactly where they are, but I've found that I'm getting a good reading in one spot and insufficient clearance in another on the same valve bucket. Both readings are on the rounded part of the cam opposite the lobe. What's going on here. Is that part of the cam not completely round opposite the lobe, and if so, where is the exact point I need to align to make an accurate measurement?
 

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the cam lobe should be 180 degrees away from the bucket

one member was having trouble with tensioner last year and it was because of corrosion in the barrel of the tensioner so if tensioner piston does not move freely might need to be removed and checked - this problem would be more common on a low mileage bike that has sat a lot
 

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gary45 said:
the cam lobe should be 180 degrees away from the bucket
This is an important point, take care that the lobe is pointing away from the bucket/valve and not just pointing straight out (horizontal) from the engine. Note that the valves are at an angle and not horizontal.
 

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Discussion Starter #4
johnbaker15 said:
This is an important point, take care that the lobe is pointing away from the bucket/valve and not just pointing straight out (horizontal) from the engine. Note that the valves are at an angle and not horizontal.
I made sure to do that, but I noticed that at what appears to be exactly 180, one set of valves was checking too tight, yet when I moved the cam a little bit more, they were within specs. Apparently, the portion of the cam on the opposite side from the lobe is not completely round. It seems there should be some mark somewhere to line up so you have the precise point where it should be measured if that is the case. Eyeballing the location does not seem good enough.
 

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gary45 said:
the cam lobe should be 180 degrees away from the bucket
I have/had the same question as tonyn1. I understand the lobe should be 180 deg away from the bucket, but my question (and I think tonyn1's as well) is: does it have to be exactly 180 deg away from the bucket? What about 175? 185? etc? When I lined up the lobes I could only eyeball it and so I know that I was likely never exactly 180 deg, but I got as close as I could. I assume that the entire bottom end of the lobe is a circle with the same radius. If that assumption is correct then being off a few degrees shouldn't matter, but if the lobe is not a circle on the bottom then it could make a difference.

After having taken the time to do two more readings on my valves last night, I was able to get my measurements to agree within .01mm so I'm satisfied with acting on those readings, but I still have that question in the back of my mind.

What sayeth thou?


EDIT: I posted the same time as tonyn1 responded above.

tonyn1 said:
Apparently, the portion of the cam on the opposite side from the lobe is not completely round. It seems there should be some mark somewhere to line up so you have the precise point where it should be measured if that is the case. Eyeballing the location does not seem good enough.
Can anyone confirm this assertion?
 

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it is not easy to tell when it is precisely at 180, so if I get proper clearance I am happy, the 1/2 the cam surface away from the lobe is not necessarily a 1/2 circle depends on where the lift starts/stops
 

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Discussion Starter #7
gary45 said:
it is not easy to tell when it is precisely at 180, so if I get proper clearance I am happy, the 1/2 the cam surface away from the lobe is not necessarily a 1/2 circle depends on where the lift starts/stops
Yes, but the problem is I get proper clearance at one point and then it measures too tight a few degrees away, so it is a big question mark where the correct point is to measure. I don't know why the cam would have a different radius on the side away from the lobe. It seems that the valve should be either open or closed, depending on where in the cycle it needs to be, and should be closed all the way when it is not in contact with the lobe. Can BMW possibly be that sloppy in grinding their cams?
 

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Generally you want the lobe point to be perpendicular to the bucket face. Should be easy to eye ball and +/-5 degrees should not give a change in reading.

Use the feeler gages as a single blade, not in a set. That way you use the correct force to insert it. A heavy fist with a blade in the set can easily depress the valve sping and give a false reading. You should consider the clearance as passing if, with and oily hand, you can insert the single blade easily. Make sure the blade is in good condition as well ith no bends or scratches.
 

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Discussion Starter #9
jzeiler said:
Generally you want the lobe point to be perpendicular to the bucket face. Should be easy to eye ball and +/-5 degrees should not give a change in reading.

Use the feeler gages as a single blade, not in a set. That way you use the correct force to insert it. A heavy fist with a blade in the set can easily depress the valve sping and give a false reading. You should consider the clearance as passing if, with and oily hand, you can insert the single blade easily. Make sure the blade is in good condition as well ith no bends or scratches.
That's my trouble. A few degrees IS making a difference.
 

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tonyn1 said:
Yes, but the problem is I get proper clearance at one point and then it measures too tight a few degrees away, so it is a big question mark where the correct point is to measure. I don't know why the cam would have a different radius on the side away from the lobe. It seems that the valve should be either open or closed, depending on where in the cycle it needs to be, and should be closed all the way when it is not in contact with the lobe. Can BMW possibly be that sloppy in grinding their cams?
valves are not either open or closed they are gradually lifted and gradually closed - at very high speeds - no square edges, the lift is started depending on valve timing just after the center opposite the lobe so as long as you can measure clearance just as John mentioned you will be OK - the valves are only closed for a tiny period of time - and it is difficult to tell precisely the degrees - if you are only finding a problem with only one valve it is possible that one could be machined a tiny bit different - sounds interesting - tiny difference in the timing of that one cylinder - not likely you can tell when it is running
 

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The part of the lobe opposite the nose is called the base, and without looking at the specific cam profile I'd expect the base circle to be an arc with a constant radius for at least 45deg either way from the center of the lobe. The valves are closed for at least 120deg of camshaft rotation in a typical racing camshaft, and even longer in a typical street cam. That means it is not critical to have the nose pointing exactly 180deg away from the follower. If rotating the lobe ±5deg like you say gives you varying clearance over the base part of the profile, you either have a mechanical problem or your measuring technique needs a little attention. I doubt you'll have a mechanical problem though, the base part of the cam typically sees no wear. Perhaps you are using excessive force inserting the feeler gauge? Or the feeler gauge blade is damaged or of suspect quality? Or you are stacking the feeler gauge blades?
 

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just to confuse things further - pulled from an online article

Duration

Ideally, you could slam a valve open, hold it open, and then slam it closed, and many drag race camshafts attempt to perform this feat, but this harsh action is incredibly abusive on valvetrain parts, especially valves and springs. To make these parts live over hundreds of thousands of miles, the cam lobe lift curve must be gentler. The easiest way to measure the amount of time the lobe is creating lift is with degrees of duration. A long time ago, our cam-building forefathers decided to use crankshaft degrees to measure cam lobe duration. So a typical performance camshaft may have a duration of 280 crankshaft degrees. Keep in mind that a camshaft actually spins at half engine speed.

But this created confusion because all the different cam companies measured the beginning of the lift curve at different points a few thousandths of an inch above the cam's base circle. This is called advertised duration and it can get complicated because, for example, Comp Cams begins measuring its advertised duration for hydraulic lifter cams when the lifter rises 0.006 inch off the base circle. Crane uses 0.004 inch, which would make the same lobe "appear" a few degrees longer in duration because the duration would be measured over a 0.004-inch-longer distance (0.002 inch on the opening and closing sides added together). This difference between companies eventually led to the selection of 0.050 inch as the standard checking point where all the different companies' lobes can be compared. So now we have both advertised duration and duration at the 0.050-inch checking figure. Now that you have the basics, we can dive into a few more items that make camshafts complex, but also fun.






The best way to install a cam is to degree it into the engine so you know exactly "where"

For each lobe there is an opening and closing point. Let's say you are measuring an intake lobe on a camshaft in the engine using a dial indicator and a degree wheel. Once the lifter rises off the base circle 0.006 inch, let's say that the degree wheel reads 20 degrees before top dead center (BTDC) and closes 90 degrees after bottom dead center (ABDC), then you can add those two numbers together along with 180 degrees and come up with the advertised duration: 20 + 180 + 90 = 290 degrees. This same formula can also be used to determine duration at 0.050 inch tappet lift.

Duration is a major contributor to the torque curve and where it occurs in the engine's rpm band. Generally speaking, as you increase the amount of intake lobe duration, this makes for an earlier-opening and later-closing intake valve. This additional duration also extends the rpm point where peak torque occurs. This tends to increase peak hp (depending upon the other components used on the engine) while sacrificing low- and mid-range torque. Conversely, a very short duration camshaft opens the intake valve later and closes it sooner, reducing the potential for high-rpm horsepower but increasing torque at a lower engine speed.
 

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I agree with this completely. If you get a difference anywhere within 30 degrees of the lobe being straight out from the follower, there is something wrong. Cams are ground with opening/closing "ramps" to take up the clearance without "slamming", but these are only a few degrees. The valves are completely closed for over 100 degrees, so plus or minus 30 degrees should always read the same with the feeler gauge. If not, something is certainly not right.

andres said:
The part of the lobe opposite the nose is called the base, and without looking at the specific cam profile I'd expect the base circle to be an arc with a constant radius for at least 45deg either way from the center of the lobe. The valves are closed for at least 120deg of camshaft rotation in a typical racing camshaft, and even longer in a typical street cam. That means it is not critical to have the nose pointing exactly 180deg away from the follower. If rotating the lobe ±5deg like you say gives you varying clearance over the base part of the profile, you either have a mechanical problem or your measuring technique needs a little attention. I doubt you'll have a mechanical problem though, the base part of the cam typically sees no wear. Perhaps you are using excessive force inserting the feeler gauge? Or the feeler gauge blade is damaged or of suspect quality? Or you are stacking the feeler gauge blades?
 

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Discussion Starter #14
andres said:
The part of the lobe opposite the nose is called the base, and without looking at the specific cam profile I'd expect the base circle to be an arc with a constant radius for at least 45deg either way from the center of the lobe. The valves are closed for at least 120deg of camshaft rotation in a typical racing camshaft, and even longer in a typical street cam. That means it is not critical to have the nose pointing exactly 180deg away from the follower. If rotating the lobe ±5deg like you say gives you varying clearance over the base part of the profile, you either have a mechanical problem or your measuring technique needs a little attention. I doubt you'll have a mechanical problem though, the base part of the cam typically sees no wear. Perhaps you are using excessive force inserting the feeler gauge? Or the feeler gauge blade is damaged or of suspect quality? Or you are stacking the feeler gauge blades?
No, I'm not using excessive force. It is too tight at one point, so I can't even get the .015 in there. I can at a few degrees away and that's the problem. I'm not stacking either, as I have separate gauges with plastic handles.
 

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Without going into a detailed inspection and analysis it is virtually impossible to determine the cause of your problem, if it really is a problem. If the 0.15mm feeler is a fairly tight fit, even a few microns will prevent it from sliding in at another position. It may be a miniscule irregularity in the surface or the base profile of the cam, but because it is on the base profile a few microns doesn't really matter because of the clearance. You may want to try and insert a thinner feeler gauge, say 0.14mm. If the 0.15mm doesn't fit but the 0.14mm does, the difference is only 10 microns or less than 0.0005 of an inch. We may be splitting hairs here! Keep in mind the bucket thickness jump in .05mm (50 micron) increments.

The question however is how to set your valves. My advice would be to set the cam lobe to where you feel comfortable it points 180deg away from the follower, and use the clearance obtained in this position to determine what adjustment needs to be made. We are talking about a 0.15mm feeler gauge which means you are at the bottom of the range for the inlet valves, and if any adjustment is needed you will increase the clearance which will then be closer to the upper limit of 0.20mm because of the bucket incremental step size. A few microns either way will make no difference.
 

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Discussion Starter #16
I'm assuming that the valve position should be checked when the cylinder is at TDC, so since I've got the plugs out already, I'll be able to check that and check the gap there.
 

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tonyn1 said:
I'm assuming that the valve position should be checked when the cylinder is at TDC, so since I've got the plugs out already, I'll be able to check that and check the gap there.
Be very careful that nothing falls in the combustion chamber since you removed the plugs. A small piece or carbon deposit could find its way between a valve and its seat and would give you a false reading.
 

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tonyn1 said:
I'm assuming that the valve position should be checked when the cylinder is at TDC, so since I've got the plugs out already, I'll be able to check that and check the gap there.


You should never remove the plugs before taking the clearance readings on the LT engine. That is one very glaring mistake in the Gunsmoke site directions.

TDC is good enough, as long as the cam lobes are pointing away from the cam lobes approximately the same angle. At compression stroke TDC, you can check both intake and exhaust valves on that cylinder.
 

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Discussion Starter #19
dshealey said:
You should never remove the plugs before taking the clearance readings on the LT engine. That is one very glaring mistake in the Gunsmoke site directions.

TDC is good enough, as long as the cam lobes are pointing away from the cam lobes approximately the same angle. At compression stroke TDC, you can check both intake and exhaust valves on that cylinder.
Yea, I forgot about that, but the engine is pretty hard to turn over with them in.
 

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Discussion Starter #20 (Edited)
I just found out that trying to measure at TDC does not work as neither intake or exhaust lobe for that cylinder is directly 180 degrees away from the buckets at that position. They are both closed however as they should be. I measured there and got a good reading on one valve and tight on the other. I know you're not supposed to read it there but why not? Why do they measure it where they do? If the radius was consistent on the backside, you should be able to measure it anywhere, but apparently it's not. You would think you would want to find the tightest spot on the back radius. If you check it at the point they say and it's OK there but is tight in another spot, it seems to me that you would have the valve opening slightly when the engine was hot at the tightest spot. But since everything I've read says to check it at 180 degrees away, that's what I'll do, but I would still like to understand what's going on with this and why they check it at the place they do. Anyhow, I was wondering when a valve is considered too tight? I can get my gauge under one valve with a little work, but not pushing enough to bend the gauge. Is that too tight? If I replace the bucket, I may end up being too loose, which may be a better thing with exhaust valves as I've heard they tend to tighten and intakes tend to loosen. So which way do I go here? Do I err on the side of going too loose on the exhaust and a little too tight on the intakes or loose on both. It's hard to get exact as the buckets only come in .05 increments. I would think if anything it's better to err on the side of too loose due to what seems to be inconsistency in the cam radius. Sorry if I sound anal about this, but I plan on putting a lot of miles on the bike this summer, and want to make sure I don't have any problems.
 
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