GS550 Valve Clearances

[bill_face]

Hello all,

I'm trying to chase down what is causing my GS to have hard starting issues. I have a bit of a head gasket leak and slightly low compression, but in the interest of looking for the easiest thing to fix first, I'm investigating valve clearances.

The manual says to have between 0.03 & 0.08mm clearance in one of two positions (egg up or on its side). I would assume that these postions would give the same reading but mine seems to vary quite a lot between the two positions. i.e 0.07mm differnce between the two positions in several cases, and none that give the same reading.

Assuming this to be a problem, what could be causing it? Wonky cams?

There are a couple of underspec valves which I believe will cause hard starting

 

[Nessism]

This is the correct way to position the cams. Use .05mm as your minimum. It's perfectly safe to use .12mm as the upper limit. Loose protects the engine. I'd target .08mm or so.

1) Rotate engine until #1 exhaust cam lobe is pointing forward, parallel to the gasket surface, then measure #1 & #2 exhaust valves.
2) Rotate engine until #4 exhaust cam lobe is pointing forward........................................... ..............................#4 & #3 exhaust valves.
3) Rotate engine until #1 intake cam lobe is pointing straight up, perpendicular to the gasket surface, then measure #1 & #2 intake valves.
4) Rotate engine until #4 exhaust cam lobe is pointing straight up................................................ ................................#4 $ #3 intake valves.​

 

[unfocused]

I measure with the lobe in the up position and I look for something above .06mm. My feelings are that anything under .06mm is too tight. I look for between .08 and .10. I do live in Florida USA and I factor this into my adjustments as it can get hot here.

Although Nessim is absolutely correct with the procedure, I do mine one at a time just for safe keeping. I've done this on several 8V engines with no issues.

If you still have points ignition, please check these as well. Check your spark plug caps - you can disassemble and clean. If you have a DVOM, check for resistance.

 

[Nessism]

I measure with the lobe in the up position and I look for something above .06mm. My feelings are that anything under .06mm is too tight. I look for between .08 and .10. I do live in Florida USA and I factor this into my adjustments as it can get hot here.

Although Nessim is absolutely correct with the procedure, I do mine one at a time just for safe keeping. I've done this on several 8V engines with no issues.

If you still have points ignition, please check these as well. Check your spark plug caps - you can disassemble and clean. If you have a DVOM, check for resistance.

The factory specified cam positions are best, because they assure that the adjacent valve to the one you are measuring is not depressed. If the adjacent valve is depressed, the spring will push up on the cam, skewing it in the journal clearance. This results in your measured valve reading more than it should by .03mm or so.

 

[unfocused]

The factory specified cam positions are best, because they assure that the adjacent valve to the one you are measuring is not depressed. If the adjacent valve is depressed, the spring will push up on the cam, skewing it in the journal clearance. This results in your measured valve reading more than it should by .03mm or so.

With all due respect - I was just adding how my adjust my valves.
Sorry if you feel I've added something wrong but it works for me.

I'll show myself the door and stop coming here

 

[Nessism]

With all due respect - I was just adding how my adjust my valves.
Sorry if you feel I've added something wrong but it works for me.

I'll show myself the door and stop coming here

I did not insult you, I simply pointed out why positioning the cams such as you do will lead to incorrect measurements. Do as you wish. Just realize that many newbies come here to learn how to maintain their bikes, so our posts can, and often will, influence how others go about these tasks.

 

[Cipher]

With all due respect - I was just adding how my adjust my valves.
Sorry if you feel I've added something wrong but it works for me.

I'll show myself the door and stop coming here

Grow up ffs. The fsm procedure was pointed out as being preferable.

 

[Datsa Noydb]

As usual, Nessism is absolutely correct. Unfortunate that someone who has been here almost five years did not recognize that.

 

[Grimly]

The factory specified cam positions are best, because they assure that the adjacent valve to the one you are measuring is not depressed. If the adjacent valve is depressed, the spring will push up on the cam, skewing it in the journal clearance. This results in your measured valve reading more than it should by .03mm or so.

For the first 20 years of GS ownership I was using the simple method and it worked fine, however I was always aiming for the max clearance to get more time between checks. Turned out the type of use I was giving the bikes (long continuous runs at steady revs) was conducive to long intervals between necessary changes. So that worked out fine for me.*
However, when the bikes retired from that life and became more used in a general capacity and got more rev-happy, I found the gaps closing up more rapidly. Not by an alarming amount, just more like Suzuki expected them to.
For the past decade I've used the workshop method as espoused by Nessism and been happy enough with it.

* Oh, and the longest I ever chanced between checks using the first method (and long-distance useage pattern) was around 20K. I'd previously checked them at 10K, found no change, checked another 15K later and nothing... so the valves settled down under that regime and finally started to show some changes around 20K.

 

[LMARJ2434]

Hmm, I just did this on my 81 650GS and thought I was good to go, followed the book, which looks something like what Nessism posted above. Should I be concerned that I am too tight?
Intake 1 - 4: 0.03, 0.06, 0.07, 0.05 and exhaust 0.07, 0.05, 0.04, 0.06
I figured being in the book range of 0.03mm-0.008mm was the golden ticket but it was mentioned above 0.06mm to 0.12mm is better. Engine has a rattle at 5000rpm that I thought was the cam chain but could it be because of the tight clearances?

 

[Rich82GS750TZ]

From what I’ve always read, you have more to worry about with valve clearance being too small and less noisy.

 

[Burque73]

From what I’ve always read, you have more to worry about with valve clearance being too small and less noisy.

Slappy valves are happy valves :dancing: