Valve clearances

[mike1414]

Hey all, so as recommended on a different post in the carb section, my motorcycle has been idling/throttling poorly. I though it was carbs, but was advised to check the valves. This was my first time every breaking an engine open (albeit just the top end), and it was pretty exciting I must say.

I went out today and purchased a Napa feeler gauge with the thinnest feeler at 0.038mm/0.0015". Now, I used BassCliff (http://members.dslextreme.com/users/bikecliff/images/gs850valve_adjust.pdf) and a different fellow's (http://www.motorcycleclassics.com/mc-how-to/suzuki-gs750-valve-adjustment-zmmz16sozhur) write-ups for checking and changing valves. From what I have read in the forum, the normal clearances are 0.03-0.08mm, correct? Upon checking exhaust clearance with the exhaust #1 lobe facing frontward and parallel to the block for #1/#2 and the lobe for #4 front/parallel for exhaust #3/#4, I was unable to get the 0.038mm feeler between the posterior lobe/shim on any. With regards to the intake clearances, I set #1 intake/#4 intake lobes respectively facing upward, and again was unable to get the 0.038mm feeler on any of the intake clearances with the exception of exhaust #2 which allowed the 0.038mm, but did not allow the next step up which is 0.051mm/0.002".

So, that being said, does it sound like I am doing this wrong, or is everything so worn out that it really is that tight? Now, furthermore, how do I go about purchasing new shims accordingly? If I understand correctly, the more worn the shims = the more tight the clearances; so would I purchase a thinner shim?

Any and all input is appreciated.

Thanks,

Mike

 

[Nessism]

Hi Mike,

Good thing you are doing the valves because they tighten with use and yours are under the minimum limit now. You are going to have to move those valves that are too tight one or maybe two shim sizes thinner now. You best take inventory of the shims you have and then figure out what you need to order. Remember to never turn over the engine with a shim removed. Also, follow BassCliff's method, which matches the factory service manual, on how to position the cams. That's the proper method.

Good luck

 

[mike1414]

Thank you so much for the quick response, sir! I can always count on you all for the appropriate help. So let's say, hypothetically, that my current shims (I do not yet have the MotionPro tool to remove them) are 2.60. Should I get both 1 and 2 sizes down in terms of shims, which would be 2.55 and 2.50?

 

[DohcBikes]

just so you know it's not the shims that are worn but the valve face and seat

always measure the shims you take out and the ones you put in, regardless of the markings

 

[mike1414]

Noted. Even still, is my assumption correct in terms of the sizing I should get? Like I said, hypothetical, but if I currently have 2.60 in, would the inadequate clearances more than likely be fixed through either 2.55 or 2.50? Or would I need to go thinner?

 

[DohcBikes]

use the shim that gets you on the loose side of in spec. if you have your spec correct at .03-.08mm, then there will only be one correct shim. In other words, if your shim will land your clearance at .03mm, use the next thinner shim so you instead end up at .08mm, other wise you'll be doing this again very soon. people have the hardest time with shim math, I don't get it.

 

[Nessism]

Noted. Even still, is my assumption correct in terms of the sizing I should get? Like I said, hypothetical, but if I currently have 2.60 in, would the inadequate clearances more than likely be fixed through either 2.55 or 2.50? Or would I need to go thinner?

That should do it. Since the valves tighten with mileage you will need the 2.50 eventually even if the 2.55 fixes it up for now.

 

[mike1414]

Fantastic. Thanks for the help, fellows. Happy to get this thing figured out

 

[Steve]

A tip before you go wild ordering shims:

First of all, you don't really need the Motion Pro tool. I have one and find it is awkward and dangerous to use, but others have no problems. I prefer to use the zip-tie method to hold the valves open while I check/change the shim.

Next, Inspect EVERY shim and record its size. (by the way, take a look at the offer in my sig, over 1000 people have found it to be a handy tool). Be sure to put each shim back in place before moving the crank to inspect another shim. When you have found your thinnest shim, take it out, put a quarter in its place. Move that thinnest shim around to the spots that have larger shims to see if that size is small enough. You will have a better idea on what size shims you will need, but will likely still have to guess on a few of them.

At least you seem to have grasped the concept of correct positioning of the cams. That is, as long as you checked both valves on that side of the cam without moving anything.

Lastly, there is a GSR Shim Exchange Club. When you figure out what you might need, contact member ghostgs1 and let him know how many of what size shims you want. Be sure to add a few extras in varying sizes to make sure you have what you need. When you are done, I think the process is that you send back what you took out and what you did not use, along with a donation to cover his expense of sending the shims to you. Extra donations are seldom refused, I'm sure. I don't know for sure that this is accurate, as I don't use the Club (I have my own stash), but I think that's how it works.

.

 

[mike1414]

Thank you for the valuable input! I actually have your spreadsheet on hand from my previous motorcycle, just did not end up tackling the job then. I ended up ordering the MotionPro tool, hopefully that will help, but we will see. I think that I certainly will discuss with ghostgs1 this shim-exchange. Hopefully I can make this a speedy process and get back on the road soon.

 

[sacruickshank]

At the risk of highjacking the thread, I have a directly related question. Bike is an '83 GS450L, 22500 miles, and I have no idea if the valves have ever been checked. The left side intake valve is fine, but the other three are all tight, to the point where an .02 mm feeler won't pass. I suspect some "gaps" are non-existent, i.e. have constant contact between the cam and the shim, because some of the cams have a straight line of visible wear, roughly 1mm wide around the profile of the cam.

This begs a few questions ...

1.) If there has been constant contact between cam and valve shim, how likely is engine damage? The PO was riding the bike regularly and I did a 6 mile test run before tear down. The engine ran fine, except for some lean revving likely caused by a visible gap in the airbox boot-to-carb connection.

2.) Assuming constant contact, how do you remove the shim? Will the motion pro tool (on order) depress the bucket further than the cam normally would? Or will I have to loosen the cam shaft brackets to allow some play? Hopefully its the former since i'd rather not loosen the shafts.

I assume that constant contact means I will likely need to go up two shim sizes, but we'll see.

Thanks in advance.

Steve

'83 GS450L
'82 GS850L
and some newer bikes

 

[jsandidge]

If the bike was running well aside from the revving, you're probably ok. And yes, the motion pro tool will depress the bucket far enough to get the shim out. Be sure not to rotate the engine unless all shims are in place.

 

[Steve]

At the risk of highjacking the thread, I have a directly related question.

Yes, you are hijacking. Yes, it's related, but it would have been better to start your own thread. There is no charge or penalty for that.

..., 22500 miles, and I have no idea if the valves have ever been checked.

Assume that they haven't. At most, it might have gotten serviced at the recommended 600 mile check, maybe at 3,000, but certainly not since then.

The left side intake valve is fine, but the other three are all tight, to the point where an .02 mm feeler won't pass. I suspect some "gaps" are non-existent, i.e. have constant contact between the cam and the shim, because some of the cams have a straight line of visible wear, roughly 1mm wide around the profile of the cam.

Can't say anything about your "wear line", but it's possible for the gaps to be too small to accept a feeler, but the actual clearance is still larger than zero.

1.) If there has been constant contact between cam and valve shim, how likely is engine damage? The PO was riding the bike regularly and I did a 6 mile test run before tear down. The engine ran fine, except for some lean revving likely caused by a visible gap in the airbox boot-to-carb connection.

If the bike started easily and ran well, there is likely no damage (yet). As mentioned earlier, just because the clearance was less than your feeler could measure does not mean that there was "constant contact".

2.) Assuming constant contact, how do you remove the shim? Will the motion pro tool (on order) depress the bucket further than the cam normally would? Or will I have to loosen the cam shaft brackets to allow some play? Hopefully its the former since i'd rather not loosen the shafts.

The Motion Pro tool won't necessarily open the valve any farther, it just does it by not pushing on the shim. It pushes on the edge of the bucket, instead. Personally, I will say "good luck" using the tool. I have never been able to use it sucessfully and prefer to use the "zip-tie method", which uses a folded zip-tie that is inserted through the spark plug hole, under the edge of the valve. This holds the valve open enough without damage and will not slip out. There is no need to loosen the cams or the tensioner.

I assume that constant contact means I will likely need to go up two shim sizes, but we'll see.

I'll say again, there is no guarantee that you have actual contact. The fact that the bike starts and runs implies that the valves are closing. It is possible that they are closing with 0.01mm clearance on the cam, but you can't measure that with your feelers. If that is the case, one shim size will increase the clearance to 0.06mm, which is just above the middle of the range. By the way, you need to go DOWN in shim size, not up.

This would also be a good time to introduce you to our library, where you can definitely reach sensory overload with information about your bike.

Also a good time to invite you to take advantage of the offer in my signature.
The spreadsheet will help you figure out what shims you might need and is a handy service reminder tool.

.

 

[sam000lee]

sacruickshank - I'm in your area and have a gone through the GS shimming a few times (GS750 and GS450's). Sending you a PM.