GS850 valve clearance: Cam lobe position

[uteman]

The manuals for these bikes show that the shim clearance can be measured with the cam lobe pointing upwards or in a position that would put the lobe at a horizontal position.
I quite understand that but if I set number 1 exhaust in vertical position and number 2 in horizontal then place them in the opposite positions I do not have consistent readings.
Has anyone else found this or do I have some bad cams in this old machine?

 

[cowboyup3371]

Follow the procedures outlined on Basscliff's website and you'll do it just fine. Also reach out to Steve (name and username) for his adjustment spreadsheet by sending him an email

http://members.dslextreme.com/users/bikecliff/images/gs850valve_adjust.pdf

 

[Redman]

.... if I set number 1 exhaust in vertical position and number 2 in horizontal then place them in the opposite positions I do not have consistent readings. ....
...

As Steve explained to me; That is because while checking the one that is one vertical the other one has the valve depressed some and that valve spring pressure is pushing the cam around some.

If ignore that sketch that shows the cam vertical, and follow the written procedure, then can check two at a time, and take much less time-effort turning the engine to different positions.

 

[uteman]

Missing the point I think

Missing the point I think

Follow the procedures outlined on Basscliff's website and you'll do it just fine. Also reach out to Steve (name and username) for his adjustment spreadsheet by sending him an email

http://members.dslextreme.com/users/bikecliff/images/gs850valve_adjust.pdf

Firstly: In the valve adjust procedure in the link provided the guy suggests using a pair of tweezers to remove the shims.
Not the easiest method. Use an extendable magnet tool.

I fully understand that two clearances can be checked at once.
However if I have say .0035" clearance on number 1 when lobe is vertical then according to procedure I should also have .0035" clearance if I put that lobe in the position that number 2 was as according to procedure I could set number 2 at the same time as I was doing number 1 so it should not matter which plane either lobe is in they should have constant clearance when in either the vertical or horizontal plane.
This is not proving to be the case so I am setting all with lobes in vertical position.
I strongly suspect that the cam profiles are worn out of shape. I do hope this issue is now clear to the reader.
I just wondered if anyone else had experienced this and do not need "how to" instructions.
Normally I would always set valve clearances on back of cam so that is what I m doing now.

 

[Nessism]

Firstly: In the valve adjust procedure in the link provided the guy suggests using a pair of tweezers to remove the shims.
Not the easiest method. Use an extendable magnet tool.

I fully understand that two clearances can be checked at once.
However if I have say .0035" clearance on number 1 when lobe is vertical then according to procedure I should also have .0035" clearance if I put that lobe in the position that number 2 was as according to procedure I could set number 2 at the same time as I was doing number 1 so it should not matter which plane either lobe is in they should have constant clearance when in either the vertical or horizontal plane.
This is not proving to be the case so I am setting all with lobes in vertical position.
I strongly suspect that the cam profiles are worn out of shape. I do hope this issue is now clear to the reader.
I just wondered if anyone else had experienced this and do not need "how to" instructions.
Normally I would always set valve clearances on back of cam so that is what I m doing now.

The idea is to have two adjacent valves on the base circle at the same time when you check the clearance. If the adjacent valve to the one you are checking is depressed, the adjacent valve will push up on the cam and skew it in the journal clearance which can change your clearance measurement by .04mm or so. Bottom line, if the adjacent valve is depressed the measured clearance will falsely suggest more clearance than actually is the case.

If don't want to follow the factory method I'd be sure to do the following: 1) make sure the valve you are checking is on the base circle, and 2) make sure the adjacent valve IS depressed, and 3) move the clearance range up from .03-.08mm to .07-.13mm. You can safely to go .15mm even. Kawasaki KZ bikes use that much clearance and the GS engine is a copy of the KZ.

 

[Redman]

.....
I just wondered if anyone else had experienced this and do not need "how to" instructions.......

Yes, I had that experience.
I noticed that if had the cam vertical (straight up, inline with the valve stem) would get a different reading than if had the cam pointed one way or the other. And it seemed to me that the sketch in the manaul didnt seem consistent with the instructions.
THe instructions are such that can check two at time. In discussions with Steve he explained to me that in that position, neither cam will be pushing against a valve spring. If one cam is pushing against a valve spring then it is pushing around the cam and effecting the clearance reading of the other cam.

 

[Steve]

Why all the resistance to do it the right way? :-k

Yes, the picture in all the manuals is goofy. It is very confusing. The Suzuki manual is the only one that puts into words what really works. They start the procedure with EX 1 and EX 2.

1. With the lobe on EX 1 pointing FORWARD and EX 2 pointing UP, you will see that neither one is pushing down against a spring. With the cam in that position and without moving anything, measure BOTH clearances.

2. Use the 19mm hex on the right end of the crank to rotate the crank 180?.

3. You will now find that IN 1 is pointing UP and IN 2 is pointing REARWARD. With the cam in that position and without moving anything, measure BOTH clearances.

4. Use the 19mm hex on the right end of the crank to rotate the crank another 180?.

5. You will now find that EX 4 is pointing FORWARD and EX 3 is pointing UP. With the cam in that position and without moving anything, measure BOTH clearances.

6. Use the 19mm hex on the right end of the crank to rotate the crank a final 180?.

7. You will now find that IN 4 is pointing UP and IN 3 is pointing REARWARD. You guessed it, with the cam in that position and without moving anything, measure BOTH clearances.

As Nessism pointed out in post #5, if one of the lobes is pushing against a spring on that side of the cam, it will push the cam off-center, adding some false clearance on the lobe that is not pushing against a spring. If you then reduce the clearance to what you think is correct, when things return back to 'normal', you will have too little clearance. Since clearance is already VERY small, any reduction will get you into dangerous territory rather quickly.

In the end, it's your bike, feel free to do it any way you want, but we will stay tuned for the thread that says:
"Help, I have burned my valves, what's it going to take to rebuild the head?"

.

 

[cowboyup3371]

Firstly: In the valve adjust procedure in the link provided the guy suggests using a pair of tweezers to remove the shims.
Not the easiest method. Use an extendable magnet tool.

Not quite sure what kind of tweezers you use but I have never had a problem.

I read your question very well but I have again never had a problem following the procedures Cliff put together on his site to the letter. My measurements stay pretty close to what they should be.

 

[uteman]

Steve: I am not resisting "doing it the right way"
I think I will bow out of this as I do not seem to be able to get my question across.
However I do appreciate all contributions to my post.
One always learns something as I have from this.
I strongly suspect that this old bike has worn cam lobes making it almost impossible to get consistent valve clearance readings.
If anyone thinks that I do not know what I am doing with a simple job like setting valve clearance then I am sorry I asked the question which was simply to see if anyone else had inconsistent readings from the vertical and horizontal positions which I am putting down to worn lobes although Nessism may have some good points.
I have set this up enough to give the engine a run after building it from scratch and will go back and recheck clearances after an initial engine run. I will take in all advice given.
Thanks for all. Over and Out!

 

[Brendan W]

Why all the resistance to do it the right way? :-k

ROFLMAO. I detect tongue firmly in cheek. This has to the the closest thing to normal status around here

I think Uteman's question is fair.
On the face of it you have two lobes, neither of which is supposed to touching and it matters which way they are not touching.
It's reasonable to pause here and ask why.
The answer lies on the far side and the cam loading going on over there.
Cams move up and down and around and the gaps we are talking about are tiny. To my mind the chances of getting the same clearances at the different lobe positions is remote.
This raises the interesting question of which is the 'right' clearance. I can accept that they are different but they have to be consistent.
The most likely answer to that question is neither. One of them got selected and defined as 'the procedure'. I figure that you could go the other way and most likely have a whole new different set of standard clearances to work with. Then nobody is GS land would have a clue what you were on about.

 

[Nessism]

The main reason for the inconsistent readings when the cam is positioned at different angles is not due to wear of the lobe. It's because the cam moves around inside the cam bearing journal clearance and is being skewed by what the other 3 valves on that same camshaft are doing. This skewing is only .001" or .002" but that's enough to throw off the measured readings. That's why it's best to just follow the Suzuki specified procedure and not waste time questioning.

1E facing gasket surface: check 1E and 2E
4E facing gasket surface: check 4E and 3E

1I pointing up at 90 degrees to gasket surface: check 1I and 2I
4I pointing up at 90 degrees to gasket surface: check 4I and 3I

It's very simple.

Stock clearance is .03-.08mm but shooting higher is a safe bet. .05-.12 is good, but I'd target the higher end of this range because as the valves wear the clearance goes down.

Good luck

 

[Redman]

............. I do not seem to be able to get my question across...........

My apologies if I haven't understood you question-situation.

You do seem experienced and have done a lot with the bike.

To review, if you care to:
Your situation is that you noticed that get different clearance if cam layed over one way verses straight up verses laid over the other way, all still with clearance on the round back side, off the lobe.

You question is/was: has anybody noticed?
Some folks said "yes".
Some folks said how that happens.
Some folks said how to avoid it (or maybe they only said "do it this way" weither or not they knew that avoiding your situation is why do it that way).

.

 

[uteman]

I want to ensure all that at no time have I wanted to appear disrespectful of what contributors have written to me.
I even removed number 2 shim whilst checking clearance on number 1 in different planes so as not to have an altered reading due to "loading" forcing the came upwards.
I do feel that with no loading from an adjacent lobe that the back of the cam is best place to measure and can understand that if doing two at once as per the procedure one would need to adhere to the written procedure or one of the two will be away from optimum measuring points.
However right now I feel like I have been bitten by a big black dog (depression) when I think that I may have offended a fellow GS Resources contributor.
This forum has been very valuable to me and I respect all who contribute.
I started the bike yesterday after working on it (for a friend at no cost) over the last two years.
I cannot describe just what a mess this was at the start and am proud of what it is now.
Before I do carb tuning I will go back and re-check all valve clearances.
My History: I am 77 years old, trained and qualified as a mechanic in my youth but did not always work in that field

 

[Brendan W]

I want to ensure all that at no time have I wanted to appear disrespectful of what contributors have written to me.
I even removed number 2 shim whilst checking clearance on number 1 in different planes so as not to have an altered reading due to "loading" forcing the came upwards.
I do feel that with no loading from an adjacent lobe that the back of the cam is best place to measure and can understand that if doing two at once as per the procedure one would need to adhere to the written procedure or one of the two will be away from optimum measuring points.
However right now I feel like I have been bitten by a big black dog (depression) when I think that I may have offended a fellow GS Resources contributor.
This forum has been very valuable to me and I respect all who contribute.
I started the bike yesterday after working on it (for a friend at no cost) over the last two years.
I cannot describe just what a mess this was at the start and am proud of what it is now.
Before I do carb tuning I will go back and re-check all valve clearances.
My History: I am 77 years old, trained and qualified as a mechanic in my youth but did not always work in that field

No worries. I think I can safely speak for a sizeable fraction of the contributors on here and make the following observations.
We're here to help.
We don't get offended.
Keyboard communication is a minefield of misunderstandings.
Tell the dog to go walkabout

 

[Redman]

.............
I even removed number 2 shim whilst checking clearance on number 1 in different planes so as not to have an altered reading due to "loading" forcing the came upwards.
...........

<<Roseanna Dana voice>> Oh.... Never mind.


Again, you do sound experienced and knowledgeable.

 

[Steve]

This skewing is only .001 or .002 but that's enough to throw off the measured readings.

Stock clearance is .03-.08mm but shooting higher is a safe bet.

Do the math on the stock clearance, you will find that it is .0012 to .0031". That means that the amount of the skewing is over half of the allowable range. Shooting for the larger end of the range is better (in more ways than one).

I even removed number 2 shim whilst checking clearance on number 1 in different planes so as not to have an altered reading due to "loading" forcing the came upwards.

Hopefully you did not rotate the crank while the shim was out. The edges of the cam lobe will be chipped by the edges of the bucket.

I do feel that with no loading from an adjacent lobe that the back of the cam is best place to measure and can understand that if doing two at once as per the procedure one would need to adhere to the written procedure or one of the two will be away from optimum measuring points.

There is no "optimum place" on the cam LOBE for measuring clearance, you have to look at the ENTIRE CAM. You mention removing a shim to remove any loading on an adjacent lobe. That is SO easily accomplished by simply positioning the lobes as described above, with both lobes on that side of the cam pointing away from their respective valves at about a 45? angle, so neither one is pushing against a spring.

Hopefully you see this as an "Ahaa" moment, recognize its simplicity and move on.

.

 

[hannibal]

I'll take a stab at it. If you check as described (just an example) with 1 pointing vertical and 2 pointing horizontal, neither 1 nor 2 is activating the valve. If you try to check with 1 pointing horizontal, 2 is now activating the valve. If you try to check with 2 pointing vertical, 1 is now activating the valve.

If an adjacent lobe is activating its valve, your measurement will be inaccurate. The only way to measure correctly is with 1 and 2 not activating the valve. The only time 1 and 2 are not activating a valve is when 1 is vertical and 2 is horizontal.

 

[Steve]

The only time 1 and 2 are not activating a valve is when 1 is vertical and 2 is horizontal.

That would be true for the INTAKE cam. :-k

For the EXHAUST cam, 1 would be FORWARD (horizontal) and 2 would be vertical. :encouragement:

.

 

[hannibal]

That would be true for the INTAKE cam. :-k

For the EXHAUST cam, 1 would be FORWARD (horizontal) and 2 would be vertical. :encouragement:

.

It was an example.

 

[Grimly]

I will say this; in the first few years of owning GSs I always did it the traditional way, against the heel of the cam. However, I always shot for the wide end of the clearance allowable, so it wasn't a problem. As I've pointed out before, GS engines that are racking up tens of thousands of motorway (freeway) miles at steady speeds have almost zero valve train wear anyway, so it was even less of a problem for me.