?? Valve Shim Question ??

[Jebus23]

Hello GS Community,

Today I removed my valve cover to take a few measurements on the clearances between shim and lobe before I ordered replacement shims. Just wanted to see where I stood. Anyways, my very old feeler gauge would not even fit on the smallest available blade. I have no clue what that smallest was since the rust covered the numbers. Before you all holler....I'm buying a new feeler gauge along with the tappet depressor and other necessary accessories for this job. The bike has 27,000 miles on it. The previous owner says he has never checked or adjusted these clearances. This worries me. It seems there is NO clearance whatsoever between the shim and lobe.

My questions are not really on the process. I understand how to check and replace. (It seems pretty straight forward)

1. Can somebody explain why the clearances get tighter with wear? I don't understand that.

2. I plan on shooting for a .07 clearance for all. Is this OK?

3. Since this has never been done before on this bike is it likely other parts are damaged? Ways to tell? If so what other things should I be checking and replacing?

4. Will this solve the problem I have been having with my bike described below?

Problem: The bike seems to be limited to 5,000 RPM's. It will not go over that. After about 45 minutes of riding the bike seems to "overheat" and become very hesitant, intermediately at first, and then totally bogs. This symptom is worse under a bigger load such as going up a hill. The only things that allows the bike to recover is to letting the engine cool. The valve cover also seems to be leaking a bit, spraying all over the underside of the gas tank over time (most likely an old gasket issue). In this moment of "overheating" The engine also smokes and it appears I have smoke that come out of the airbox (gas recycling hose from the top of the head?)

Overheating seems to happen when I'm stop and go a lot as opposed to open road.

This bike is parked for the winter so I have plenty of time to tackle this issue.

Thanks for reading the novel, I just needed to run this by all of you GS experts.

 

[tkent02]

Hello GS Community,

Today I removed my valve cover to take a few measurements on the clearances between shim and lobe before I ordered replacement shims. Just wanted to see where I stood. Anyways, my very old feeler gauge would not even fit on the smallest available blade. I have no clue what that smallest was since the rust covered the numbers. Before you all holler....I'm buying a new feeler gauge along with the tappet depressor and other necessary accessories for this job. The bike has 27,000 miles on it. The previous owner says he has never checked or adjusted these clearances. This worries me. It seems there is NO clearance whatsoever between the shim and lobe.

My questions are not really on the process. I understand how to check and replace. (It seems pretty straight forward)

1. Can somebody explain why the clearances get tighter with wear? I don't understand that.

2. I plan on shooting for a .07 clearance for all. Is this OK?

3. Since this has never been done before on this bike is it likely other parts are damaged? Ways to tell? If so what other things should I be checking and replacing?

4. Will this solve the problem I have been having with my bike described below?

Problem: The bike seems to be limited to 5,000 RPM's. It will not go over that. After about 45 minutes of riding the bike seems to "overheat" and become very hesitant, intermediately at first, and then totally bogs. This symptom is worse under a bigger load such as going up a hill. The only things that allows the bike to recover is to letting the engine cool. The valve cover also seems to be leaking a bit, spraying all over the underside of the gas tank over time (most likely an old gasket issue). In this moment of "overheating" The engine also smokes and it appears I have smoke that come out of the airbox (gas recycling hose from the top of the head?)

Overheating seems to happen when I'm stop and go a lot as opposed to open road.

This bike is parked for the winter so I have plenty of time to tackle this issue.

Thanks for reading the novel, I just needed to run this by all of you GS experts.

What wears is the seat, and the area where the valve contacts the seat. The valve recedes into the head so the valve stem appears to get longer, the clearance gets smaller.
Hopefully you have not done any damage, check the compression to find out.
The other issues are probably carburetion, possibly ignition too.
Which bike are we talking about?

 

[Jebus23]

Bike is a 1980 GS550E. (sorry I planned on putting that in the original post)

Carbs were dipped and sprayed. They are CLEAN.

I have a brand new Dyna S in for ignition.

Coils and wires are original however. No visible arching but I plan to replace.

Thanks for your post!

More comments Please!

 

[Nessism]

A good many GS's have died a horrible death because the valves were neglected and the valves/seats burned. The valve recedes into the head until all the clearance is gone and the valve never seats which burns the valves when hot gasses pass over them during combustion. For a neglected bike you need at least one thin checking shim; install the thin shim and then check the clearance so you can get a proper gauge on the shim that's needed. Hopefully there is not too much damage and the proper shim allows the valve to seat as it should.

The first two photos show burned valves and the last photo shows valves the way they should be.

 

[tkent02]

I have a brand new Dyna S in for ignition.

Is the ignition timing and the advance correct?

 

[almarconi]

The overheating may be due to an overly lean condition. Have you checked for air leaks around the carb intakes? Also you want to verify your timing and check your cam chain tensioner. Make sure the advance mechanism is working properly.

I had a similar problem on my KZ750. The valves had almost no clearance and the cam chain tensioner was not working properly, the engine would not rev past about 4k rpms. The engine will now pull cleanly to redline since I adjusted the valves, installed a manual cam chain tensioner and removed all the gunk from the carbs.

Carbs were dipped and sprayed. They are CLEAN.

That statement tells me that you need to remove the carbs and clean them again. Usually 3 times is the magic number for truly clean carbs. Unless you've got a ton of experience cleaning carbs, your not going to get them clean the first time. This is not an attack on you, I include myself in that group. I will usually have to pull the carbs a couple of time to get them completely clean. I have soaked them in berrymans for 24 hours, sprayd with carb cleaner, used compressed air..yada yada yada..they still need to be cleaned again.

 

[Steve]

Bike is a 1980 GS550E. (sorry I planned on putting that in the original post)

Instead of trying to remember to put it in each post, put it in a signature line, so it shows with every post that you make.

.

 

[Don-lo]

Your symptoms sound like gas is in the oil. Your carbs do not have an overflow, so a leaky petcock allows overflow that goes into the pistons and then into the crankcase. The gas vaporizes off quicker the warmer it gets, carrying oil with it, going into the airbox.

 

[Jebus23]

The advance seems to be working fine and the timing light came on at all the right points. Thats an interesting theory with the gas in the oil, however my fuel petcock is brand new. I am thinking about pulling the valves out and inspecting the springs and soaking the valves in gas. What is everyone's thoughts on this. Is there a good right up for getting to the valves? I plan on buying a manual in the next few days. Keep the feedback coming, it is very helpful.

The carbs have been off and cleaned 3 times now....the only error that could come from them is a bad part inside....and they all seemed fine, HOWEVER the retaining clip that holds in the needle valves are all off. Is this an issue? I have heard people on here that have no clips and its fine.

 

[tkent02]

I am thinking about pulling the valves out and inspecting the springs and soaking the valves in gas. What is everyone's thoughts on this. Is there a good right up for getting to the valves?

You didn't mention having low compression.
How low was it?

 

[DangerWillRobinson]

The first course of action would be a compression check.

If it's not good, shim the valves and check it again.

If it's still not good after shimming than you will probably have to pull the head and do the valves.

If valves are tight they will not close all the way or seat. That will cause them to burn because they have to seat in order to dissipate their heat to the head.

Leaky valves will also cause a lean fuel/air mixture condition as the exhaust gases contaminate the incoming charge.

The paper valve cover gasket is a single use item. Avoid scratching the head or valve cover when you clean the old one off.

 

[doctorgonzo]

Before you pull the valves out.

Are you checking them correctly, following the method in the manual? What is your smallest feel gauge, .04? A handy thing to have as Nessism said is a really thin shim (like a 2.10). Almost no matter how tight they are it lets you get a feeler in there to see where they are exactly.

You took the carbs off, pulled the rack apart and dipped the carbs overnight, then verified every passage was clean? You replaced all the little rubber o-rings in the carbs?