Valve clearance GS550 '78

[11csive]

So, I picked up an old GS550 for cheap (you American guys would laugh at the price, but for someone living in Denmark, it was cheap ) - I've been lurking around on this forum for quite a while, and now it's time for my first post.

Anyway, first thing first, did a compression test. Started at cyl. 4 (don't ask me why) and I started off happy.

#4 155 psi
#3 145 psi
#2 0 psi (bummer)
#1 150 psi

Except from cyl. 2 I find those numbers rather good for a 38 year old woman?

Next step, valve clearance check. I ended up having a lot of troubles with some screws in the engine, which took the daylight away from me faster than I liked. I only had time to check the 4 exhaust valves.

#1 0.17mm
#2 0.48mm
#3 0.11mm
#4 0.19mm

Question is, should I just get some new shims to replace the old ones, or is there something you guys recommend to check further, when one of the valves is off by that much?

The readings were done cold and with the valves in the position mentioned in the original service manual.

I hope you guys can help me out.

 

[Nessism]

The proper spec is .03-.08mm

Only one valve is remotely close (.11mm).

Yes, you need new shims. A bunch of them.

 

[dantodd]

Unless you have an incredibly tiny shim in #2 I'd suspect a bent valve stem at that clearance.

 

[Nessism]

Unless you have an incredibly tiny shim in #2 I'd suspect a bent valve stem at that clearance.

Good eye. Hopefully just a chunk of crud holding the valve open otherwise I think you are correct.

 

[Steve]

I will add another confirmation to the suspicion of a bent valve in #2.

Also, are you SURE you checked the valves with the cams in the correct positions?
Many do not realize (at first) that for the exhaust valves, you set the outer cam lobe (#1 or #4) to the FORWARD position, which places the inner lobe (#2 or #3) to the UP position. Without moving the cam, measure BOTH valves on that side of the engine. Is that the way you did it? :-k

#3 is almost close enough to leave alone. By the time you run it a bit, any small crud on the seat will be compacted a bit, leaving you with less than 0.10mm, which is our practical limit, even though Suzuki said 0.08mm.

.

 

[11csive]

Thank you for the answers.

The proper spec is .03-.08mm

Only one valve is remotely close (.11mm).

Yes, you need new shims. A bunch of them.

Sorry if my question wasn't clear enough, but I'm aware that I need new shims. I had a suspicion that something else than normal wear was causing the big gap on cyl. #2 and that is what I'm hoping to figure out with the help of you guys.

Unless you have an incredibly tiny shim in #2 I'd suspect a bent valve stem at that clearance.

Okay, this is the kind of stuff I was worried about I've got an entire day to work on the bike tomorrow, so I'll try and see if that's the case.

I will add another confirmation to the suspicion of a bent valve in #2.

Also, are you SURE you checked the valves with the cams in the correct positions?
Many do not realize (at first) that for the exhaust valves, you set the outer cam lobe (#1 or #4) to the FORWARD position, which places the inner lobe (#2 or #3) to the UP position. Without moving the cam, measure BOTH valves on that side of the engine. Is that the way you did it? :-k

#3 is almost close enough to leave alone. By the time you run it a bit, any small crud on the seat will be compacted a bit, leaving you with less than 0.10mm, which is our practical limit, even though Suzuki said 0.08mm.

.

Thank you, I'll check if the valve is bent and come back to you guys as soon as possible.

Positive. That is exactly the way I did it. Had the service manual with me, and the guide from BassCliff's website too

By the way, this is my first bike renovation. I know some basics, but I'm not exactly a pro. Learning by reading and doing. Besides from that, English isn't exactly my first language, so bear with me if I mess up some terms or isn't clear as to what I'm trying to say

 

[2BRacing]

.....Next step, valve clearance check. I ended up having a lot of troubles with some screws in the engine, which took the daylight away from me faster than I liked. I only had time to check the 4 exhaust valves.

#1 0.17mm
#2 0.48mm
#3 0.11mm
#4 0.19mm

Question is, should I just get some new shims to replace the old ones, .....

You have used the service manual and followed the correct procedure, but my concern is why the readings are so large? Are you sure you did not confuse inch and mm readings on the feeler gauges? Usually the valve clearances go smaller and are often at zero on neglected engines. That would typically result in a valve not closing completely, and therefore low or no compression. I agree that a bent valve stem could also result in no compression and the high clearance reading. However, it is unusual for only one valve to be bent when timing problems result in pistons hitting valves. Are you sure the bucket itself on that valve is free to move and is not sticking?

Measure the intake valve clearances as well. You can often swap shims around to get the correct readings, saving you the need to get so many shims. NEVER turn the engine over without a shim in each bucket, it damages the cam lobes!

Then I also suggest that you check the valve timing by setting #1 piston at TDC, making sure the arrow on the exhaust cam aligns with the cylinder head surface, and counting the number of pins between the other arrows, as described in the service manual. For a valve to be bent, it means that the valve timing must have been incorrect.

Hope you sort this problem out!

 

[11csive]

You have used the service manual and followed the correct procedure, but my concern is why the readings are so large? Are you sure you did not confuse inch and mm readings on the feeler gauges? Usually the valve clearances go smaller and are often at zero on neglected engines. That would typically result in a valve not closing completely, and therefore low or no compression. I agree that a bent valve stem could also result in no compression and the high clearance reading. However, it is unusual for only one valve to be bent when timing problems result in pistons hitting valves. Are you sure the bucket itself on that valve is free to move and is not sticking?

Measure the intake valve clearances as well. You can often swap shims around to get the correct readings, saving you the need to get so many shims. NEVER turn the engine over without a shim in each bucket, it damages the cam lobes!

Then I also suggest that you check the valve timing by setting #1 piston at TDC, making sure the arrow on the exhaust cam aligns with the cylinder head surface, and counting the number of pins between the other arrows, as described in the service manual. For a valve to be bent, it means that the valve timing must have been incorrect.

Hope you sort this problem out!

My feeler gauges are in mm, so I'm pretty sure I didn't mix up inch and mm.

I haven't done anything but to measure the clearances, as I ran out of daylight, but I'll do a recheck on every single valve + get a reading on the intake valves as well first thing tomorrow.
Was wondering about the high readings myself, as I've read everywhere on here that they tend to tighten up over the years, not the other way around, but I'm 99% sure I did everything as I should. I will however do a re-check of course, I might have done something stupid Or else the PO might have done something stupid, who knows.

I'll check the bucket too, as well as the valve timing.

Thanks a lot for the answer and for the shim swap trick, hadn't even thought about that :stupid:

 

[Steve]

..., English isn't exactly my first language, so bear with me if I mess up some terms or isn't clear as to what I'm trying to say

There is nothing wrong with your English (so far). In fact, I wish more of the 'locals' here were as eloquent and accurate as you are. :encouragement:

Thanks a lot for the answer and for the shim swap trick, hadn't even thought about that :stupid:

Keep in mind that to swap shims, you need to remove one first, so you can move it to another location. Making that 'other location' available will involve moving the crank/cam. Place a coin on the bucket in place of the shim to avoid damaging the cam lobe. I have no idea what coins you have available, but anything over 1.5mm thick and about 25-29mm diameter will work just fine. You will probably damage the surface of the coin a bit, so don't make it a valuable coin.

Feel free to take advantage of the offer in my signature for the valve adjust spreadsheet. It will help you inventory your shims and calculate your next shim size, based on current clearance and shim size.

.

 

[11csive]

There is nothing wrong with your English (so far). In fact, I wish more of the 'locals' here were as eloquent and accurate as you are. :encouragement:




Keep in mind that to swap shims, you need to remove one first, so you can move it to another location. Making that 'other location' available will involve moving the crank/cam. Place a coin on the bucket in place of the shim to avoid damaging the cam lobe. I have no idea what coins you have available, but anything over 1.5mm thick and about 25-29mm diameter will work just fine. You will probably damage the surface of the coin a bit, so don't make it a valuable coin.

Feel free to take advantage of the offer in my signature for the valve adjust spreadsheet. It will help you inventory your shims and calculate your next shim size, based on current clearance and shim size.

.

Amazing support on here. I've sent you an email

Does anyone on here know of a good guide to remove (replace) valves on a GS? Or is the service manual adequate, even for someone who haven't removed valves before?

The link on Basscliff's website doesn't work for me.

/ Simon

 

[Steve]

Why do you feel that you need to remove valves? To adjust the clearance, there is no need to remove valves, which is a job that requires several hundred dollars worth of gaskets. A mere valve adjustment might require a valve cover gasket. If prepped properly and installed correctly, they can be re-used a few times, but since you have no idea how this one was installed, it's best to have a new gasket ready.

.

 

[11csive]

Why do you feel that you need to remove valves? To adjust the clearance, there is no need to remove valves, which is a job that requires several hundred dollars worth of gaskets. A mere valve adjustment might require a valve cover gasket. If prepped properly and installed correctly, they can be re-used a few times, but since you have no idea how this one was installed, it's best to have a new gasket ready.

.

I am of course gonna check all the other things mentioned first, but since you guys suspected a bent valve stem, I assumed that, at some point, I would be forced to take out the valves to see if it's actually the case. So I was merely trying to prepare myself for the task.

Is there any easier way to check for a bent valve, besides pulling it out?

Just let me know if I'm not approaching this correctly. My lack of deep knowledge on this subject is surely making me assume wrong things from time to time

 

[Nessism]

Since it's the exhaust side valve that's in question I'd remove the exhaust system and look inside the port at the valve to see if some sort of foreign material is holding the valve open. WARNING: if the exhaust system head bolts have not been removed in a long time you must be very cautious when removing them since they tend to seize in the head and turning them out will break them off. Use heat and some penetrating oil, and a short handled wrench. Do not force these screws or you will be sorry.

Once you have the head off you can turn over the engine and inspect the valve sealing surface by looking in the port. Hopefully it's just a chunk or carbon that's stuck. Of course, check the cam timing after removing the valve cover at the same time. If the cam chain jumped the timing will be off and you will know your answer right away then.

 

[11csive]

So, had some time to spend on the bike today - lovely weather too

I started off by getting a reading on all 8 valves. Also did a re-check on the 4 exhaust valves I already checked, to see if I messed something up. Besides from going from 0.48mm to 0.49mm on cyl. 2, nothing changed.
The results are as follows:

Exhaust:
Valve clearance:
#1 0.17mm
#2 0.49mm
#3 0.12mm
#4 0.11mm

Shims:
#1 2.95mm
#2 2.90mm
#3 2.75mm
#4 2.85mm

Intake:
Valve clearance:

#1 0.08mm
#2 0.11mm
#3 0.07mm
#4 0.08mm

Shims:
#1 2.85mm
#2 2.85mm
#3 2.80mm
#4 2.85mm

We are getting close to maximum sizes on the exhaust size, am I right? (3.10mm according to the service manual) Any idea why this is happening when you guys say they tend to tighten up?

Time to add some pictures to this thread - I took some pictures of the position that I put the camshafts in before I made the valve clearance check. Just to be 100% sure I did everything as I should.

I turned the engine over to put them in the following position - cyl. 1 exhaust pointing straight forward, parallel with the engine, then checked exhaust 1 + 2.

Then I turned the engine over to put cyl. 4 in the same position as cyl. 1 in the previous picture then measuring exhaust 3 + 4.

Next thing, intake side. Turning the engine over into this position, measuring intake 1 + 2.

Aaaaaand, turning it over to place cyl 4. into the same position as cyl. 1 in the previous picture.

You guys see anything wrong here?

Next thing, I checked the valve timing. The timing is as it should be.
I lined up the 1 4 T mark with the timing mark. The 1 mark on the exhaust sprocket was parallel with the engine and I counted 20 chain pins between the #2 arrow on the exhaust sprocket and #3 arrow on the intake sprocket. This is the correct way of checking the valve timing, right?

Since it's the exhaust side valve that's in question I'd remove the exhaust system and look inside the port at the valve to see if some sort of foreign material is holding the valve open. WARNING: if the exhaust system head bolts have not been removed in a long time you must be very cautious when removing them since they tend to seize in the head and turning them out will break them off. Use heat and some penetrating oil, and a short handled wrench. Do not force these screws or you will be sorry.

Once you have the head off you can turn over the engine and inspect the valve sealing surface by looking in the port. Hopefully it's just a chunk or carbon that's stuck. Of course, check the cam timing after removing the valve cover at the same time. If the cam chain jumped the timing will be off and you will know your answer right away then.

As the last thing, I was on my way to remove the exhaust. The bolts came off pretty easily (Not stuck exhaust, so they have been removed at some point) but the tubes seems to be stuck. I didn't put a lot of time or effort into this yet, I'll give it another try when I get some time to look at it again.

Again, thanks a lot for the answers, it's really awesome to have the help from you guys as I proceed to work on the bike.

Thank you!

/Simon

 

[11csive]

Now that I'm here, where do you guys buy valve cover gaskets? Only NOS or some specific brand to go for?

/ Simon

 

[Nessism]

OEM Suzuki gaskets are best.

Regarding the shims, only 1E & 2E need to be touched. Either that engine is low mileage or someone cut the valves and shortened the stems.

If you can't see anything under #2E when you pull off the exhaust the next step is to pull the cams and remove the 2E bucket to see what's going on there. Key thing to look for is to make sure the valve stem sticks up above the keepers. If someone cut the valve stems too much the keepers may be sticking up too far.

 

[Big T]

Your readings are a bit odd. Bikes typically come with 2.75-2.85 shims new, and proper clearances. To have such thick shims and large clearances makes no sense.

You seem to have one aspect backwards. The valve clearances get smaller with miles, and thinner (not thicker) shims are needed.

As for the exhaust, just yank the tubes out of the cylinder head. There's a crush gasket in there, and it can stick everything together.

 

[11csive]

OEM Suzuki is the best.

Regarding the shims, only 1E & 2E need to be touched. Either that engine is low mileage or someone cut the valves and shortened the stems.

If you can't see anything under #2E when you pull off the exhaust the next step is to pull the cams and remove the 2E bucket to see what's going on there. Key thing to look for is to make sure the valve stem sticks up above the keepers. If someone cut the valve stems too much the keepers may be sticking up too far.

I wouldn't place my money on the low mileage guess Shortened valve stems seems more likely, especially the high readings + big shims. So you'd only touch e1 + e2 and let the other tighten up by themselves?

I'l get back to working on the bike this weekend (lot of work the next couple of days) and when I do, I'll check what's going on with the valves!

Thank you!

 

[11csive]

Your readings are a bit odd. Bikes typically come with 2.75-2.85 shims new, and proper clearances. To have such thick shims and large clearances makes no sense.

You seem to have one aspect backwards. The valve clearances get smaller with miles, and thinner (not thicker) shims are needed.

As for the exhaust, just yank the tubes out of the cylinder head. There's a crush gasket in there, and it can stick everything together.

Well I'm quite confused myself. But as Nessism pointed out, some PO might have shortened the valve stems? I don't know, seems like a good guess.

I'm not quite sure what you mean with "I got one aspect backwards"?

I'll try to put some force on the tubes and get them out.

 

[Nessism]

With mileage the valves sink into the head. When this happens the required shims get thinner and thinner.

If the engine requires cutting the valve faces and seats this exacerbates the situation even more. To correct this it's necessary to trim some material off the end of the valve. That's what I think happened to your head. The only other option I can think of is if someone replaced the head with one that was literally new, which is unlikely.