Cam Positioning - Weird Clearance Measurements

[jswhite]

Hey All,

Doing a valve clearance check on my 81' GS650G for the first time, I'm using the FSM, Clymers, and BassCliff's tutorial and came across something weird.
I am getting difference clearance readings with the two positions. Looks like the cam is either supposed to be parallel with the head pointing away from the shim, or perpendicular to the head to be measured...OK.

My EX # 4 valve is measuring .004"-.005" in the perpendicular position, and .0015"-.002" in the parallel position.
Even weirder, my EX # 2 is not measurable AKA smaller than .0015" in the perpendicular position, and .002"-.0025" in the parallel position.

1. the measurements are not the same between the two positions
2. one is looser in the perpendicular position, and the other is tighter in the perpendicular position.:upset:

This is not supposed to happen right?
Sounds like some weird cam wear?
According to BassCliffs tutorial, all my valves except one are below .0015", and only one is .0015", so one is barley in spec the rest are tight. Started swapping out shims and noticed this.

I'm just hoping I dont need a new cam

Thanks for all the help!!

 

[Nessism]

You just learned why Suzuki specified the method they do. This is all well documented in older threads here (dozens of them).

 

[Steve]

You don't get to choose one of two positions to check the clearance.

On the other hand, when you follow the factory manual, you will see that you choose the correct position and check two valves.

I am going to assume that you have the factory manual downloaded from BassCliff's site, since you mentioned it. Look on manual page 2-5, which is PDF page 24. The first thing to do is to IGNORE that goofy drawing at the top of the right column. Start with instruction #1 just below that, then continue through instruction #4 on page 2-6.

An easy way to remember how to position the cam lobes is to realize that in those positions, neither lobe on that side of the cam is pushing on a valve. If either one is pushing on a valve, it will push the cam away from it, into the bearing cap. The clearance for the oil film is only about a thousandth of an inch, but one thousandth of an inch is half of the allowable range on the valve clearance. You can easily add that amount to your clearance reading, which will give you a false reading and false sense of security.

The clearance check procedure is so easy to do, I don't know why the instructions are so hard.
1. Set EX1 cam lobe FORWARD, check EX1 and EX2.
2. Rotate the crank 1/2 turn, check IN1 and IN2.
3. Rotate the crank 1/2 turn, check EX3 and EX4.
4. Rotate the crank 1/2 turn, check IN3 and IN4.

After you have them all measured, they you can go through the process of removing shims ONE AT AT TIME to inventory them and enter the sizes in the spreadsheet. Then you can see if you have some that can be moved around to minimize how many you need to acquire from the GSR Shim Club.

By the way, the Suzuki manual is the only one that specifically says to position the cams, then measure BOTH valves on that side. The others (Clymer and Haynes) only show that goofy drawing and say "position the cams like this ...".

.

 

[jswhite]

You don't get to choose one of two positions to check the clearance.

On the other hand, when you follow the factory manual, you will see that you choose the correct position and check two valves.

I am going to assume that you have the factory manual downloaded from BassCliff's site, since you mentioned it. Look on manual page 2-5, which is PDF page 24. The first thing to do is to IGNORE that goofy drawing at the top of the right column. Start with instruction #1 just below that, then continue through instruction #4 on page 2-6.

An easy way to remember how to position the cam lobes is to realize that in those positions, neither lobe on that side of the cam is pushing on a valve. If either one is pushing on a valve, it will push the cam away from it, into the bearing cap. The clearance for the oil film is only about a thousandth of an inch, but one thousandth of an inch is half of the allowable range on the valve clearance. You can easily add that amount to your clearance reading, which will give you a false reading and false sense of security.

The clearance check procedure is so easy to do, I don't know why the instructions are so hard.
1. Set EX1 cam lobe FORWARD, check EX1 and EX2.
2. Rotate the crank 1/2 turn, check IN1 and IN2.
3. Rotate the crank 1/2 turn, check EX3 and EX4.
4. Rotate the crank 1/2 turn, check IN3 and IN4.

After you have them all measured, they you can go through the process of removing shims ONE AT AT TIME to inventory them and enter the sizes in the spreadsheet. Then you can see if you have some that can be moved around to minimize how many you need to acquire from the GSR Shim Club.

By the way, the Suzuki manual is the only one that specifically says to position the cams, then measure BOTH valves on that side. The others (Clymer and Haynes) only show that goofy drawing and say "position the cams like this ...".

.

This is good news, I was all worried about my cam wearing in a weird way and having to replace it.
I did that exact process for my first check, but the I was double checking my work and went outside the process to start measuring.
Any suggestions on how to join the shim club, cause I have some really tight valves...

 

[cowboyup3371]

Take a read of this thread in the GS Parts and Services forum

https://www.thegsresources.com/_forum/showthread.php?122394-GS-Valve-Shim-Club

Ray's screenname is GhostGS1

 

[jswhite]

Take a read of this thread in the GS Parts and Services forum

https://www.thegsresources.com/_forum/showthread.php?122394-GS-Valve-Shim-Club

Ray's screenname is GhostGS1

Got it, thanks everyone, valves measured and shims on their way!