Valve clearance, went from 270 to 260. Engine VERY hard 2 turn over bent valve?

[tussey]

So I'm checking my valves. I think I might have a bent valve. Here's why.

1) I've been running with three exhaust bolts (2 on the left, 1 on the right) for at least 5 months now. Srinath suggests my engine is probably running very hot and I may have bent a valve (http://gstwins.com/gsboard/index.php?topic=29605.msg320776#msg320776)

2) When turning the wheel in 6th gear it's pretty easy then it gets VERY hard. I mean REAL hard, like I have to use two hands and yank the wheel. It seems to do this when the cam lobe is pushing open the exhaust port on the right side (the one with 1 bolt, and the one srinath suggests is hot and may have bent).

3) On this same valve the clearance was VERY tight. I went from a 270 to a 260 (blame the previous owner!  )

Please GSTwins. What are your thoughts? Thank you. 

[gsJack]

When your turning the engine over it should go from very easy to very hard if you haven't removed the plugs.  Compression will resist the turning.  Besides you should take off the small cover at the right side of the crank and turn the engine with a wrench.  19mm box I think, turn clockwise.

If your exhaust valve was tight and you went down 2 shims in size and got clearance, you most likely don't have a bent valve or it would be sticking open.  To check, remove the plugs and hold a finger tightly over the plug hole and crank it over.  If your finger is blown out with a loud pop, you don't have a bent valve.  You have compression.   

It's been my experience that the GS500 exhaust valves tend to recede into the seats and get tight.  Intakes do not.  With 80k miles on my 97 GS the intakes still had proper clearance with the original shims and the exhaust valve shims had been reduced several times till one was down to a min shim thickness. 

It's also been my experience that GS exhaust valves break rather than bend.      You really should fix that exhaust flange bolt though.

[JamesG]

Yeah, remove the plugs and try the test again.  For a more accurate "feel" take the little round timing cover off the right side of the engine and crank the engine around with a ratchet on the end of the crank.

If it is still hard to turn with the plugs out, then yeah you've probably got lots of nice little smiliey faces in that piston face. sorry. 

[D-Day]

When your turning the engine over it should go from very easy to very hard if you haven't removed the plugs.  Compression will resist the turning.  Besides you should take off the small cover at the right side of the crank and turn the engine with a wrench.  19mm box I think, turn clockwise.

If your exhaust valve was tight and you went down 2 shims in size and got clearance, you most likely don't have a bent valve or it would be sticking open.  To check, remove the plugs and hold a finger tightly over the plug hole and crank it over.  If your finger is blown out with a loud pop, you don't have a bent valve.  You have compression.   

It's been my experience that the GS500 exhaust valves tend to recede into the seats and get tight.  Intakes do not.  With 80k miles on my 97 GS the intakes still had proper clearance with the original shims and the exhaust valve shims had been reduced several times till one was down to a min shim thickness. 

It's also been my experience that GS exhaust valves break rather than bend.      You really should fix that exhaust flange bolt though.

Hey Jack!  You are back!

[tussey]

When your turning the engine over it should go from very easy to very hard if you haven't removed the plugs.  Compression will resist the turning.  Besides you should take off the small cover at the right side of the crank and turn the engine with a wrench.  19mm box I think, turn clockwise.

If your exhaust valve was tight and you went down 2 shims in size and got clearance, you most likely don't have a bent valve or it would be sticking open.  To check, remove the plugs and hold a finger tightly over the plug hole and crank it over.  If your finger is blown out with a loud pop, you don't have a bent valve.  You have compression.   

It's been my experience that the GS500 exhaust valves tend to recede into the seats and get tight.  Intakes do not.  With 80k miles on my 97 GS the intakes still had proper clearance with the original shims and the exhaust valve shims had been reduced several times till one was down to a min shim thickness. 
It's also been my experience that GS exhaust valves break rather than bend.      You really should fix that exhaust flange bolt though.

Thank you your post was very helpful. I did take the spark plugs out when I was trying this. I accidentally tried to start it with no spark plugs too and I noticed a puff of air, so I'm sure I have compression, guess it's not a bent valve but rather a really strong spring(?). I will try turning it with a 19mm wrench.

Here is a strange thing though. I reduced the exhaust intake by .01mm and now it won't start. It was much too tight before, yet it ran. Now it has the proper clearance and doesn't start. It sounds like something is getting stuck. What I mean is that the engine will turn over a few times then stop like something is blocking the engine from turning.

I want to put the 270 back in the exhaust but I don't want to put any stress on the engine.

[gsJack]

Here is a strange thing though. I reduced the exhaust intake by .01mm and now it won't start. It was much too tight before, yet it ran. Now it has the proper clearance and doesn't start. It sounds like something is getting stuck. What I mean is that the engine will turn over a few times then stop like something is blocking the engine from turning.

I want to put the 270 back in the exhaust but I don't want to put any stress on the engine.

A 270 shim is 2.70 mm or approx .105" thick.  Reducing the shim from 270 to 260 would be a reduction of .1 mm or .004" approx.  So you reduced it .1 mm rather than .01 mm.  I had to make this amount of change a couple times on my 97 to get proper exhaust valve clearance at about 8k valve check intervals.

If you have proper clearance on all the valves or close to it, it should run.  A tight valve would make starting harder than a loose one would.  If the clearance is proper, leave the 260 shim in and look further for the problem.

Checking all the valve clearances with the nose of the cam away from the shim should be adequate but it's best to set them like shown in the Clymers with the crank on the timing mark and the cam shaft notches as shown in the diagrams.  It's a bit more accurate but not totally necessary.

Double check everything else, gas tank on, gas in tank, all wires tight at the coils and on plugs, choke hooked up properly.  Might have run the carbs out of gas while playing with it, put the fuel selector valve on prime when you try to restart to fill the carb bowls.

[Mandres]

When your turning the engine over it should go from very easy to very hard if you haven't removed the plugs.  Compression will resist the turning.  Besides you should take off the small cover at the right side of the crank and turn the engine with a wrench.  19mm box I think, turn clockwise.

If your exhaust valve was tight and you went down 2 shims in size and got clearance, you most likely don't have a bent valve or it would be sticking open.  To check, remove the plugs and hold a finger tightly over the plug hole and crank it over.  If your finger is blown out with a loud pop, you don't have a bent valve.  You have compression.   

It's been my experience that the GS500 exhaust valves tend to recede into the seats and get tight.  Intakes do not.  With 80k miles on my 97 GS the intakes still had proper clearance with the original shims and the exhaust valve shims had been reduced several times till one was down to a min shim thickness. 
It's also been my experience that GS exhaust valves break rather than bend.      You really should fix that exhaust flange bolt though.

Thank you your post was very helpful. I did take the spark plugs out when I was trying this. I accidentally tried to start it with no spark plugs too and I noticed a puff of air, so I'm sure I have compression, guess it's not a bent valve but rather a really strong spring(?). I will try turning it with a 19mm wrench.

Here is a strange thing though. I reduced the exhaust intake by .01mm and now it won't start. It was much too tight before, yet it ran. Now it has the proper clearance and doesn't start. It sounds like something is getting stuck. What I mean is that the engine will turn over a few times then stop like something is blocking the engine from turning.

I want to put the 270 back in the exhaust but I don't want to put any stress on the engine.

When you changed the shim did you use the tool to depress the bucket or did you remove the cam?  If it's the latter you might have problems.  Is the cam chain tensioner installed properly?  Did you set the timing according the manual procedure?  You said the engine turns over a few times and stops so that might indicate a binding cam chain or improper timing sequence.  If you just used the depressor tool and didn't disturb the cams then disregard that stuff.

[MarkusN]

Also, if you turned the engine backwards in your trials you might have bent/broken one of the cam chain guides. The cam chain gets very high tension when the motor is turned backwards.

[tussey]

Also, if you turned the engine backwards in your trials you might have bent/broken one of the cam chain guides. The cam chain gets very high tension when the motor is turned backwards.

how do I check for that?

[tussey]

When your turning the engine over it should go from very easy to very hard if you haven't removed the plugs.  Compression will resist the turning.  Besides you should take off the small cover at the right side of the crank and turn the engine with a wrench.  19mm box I think, turn clockwise.

If your exhaust valve was tight and you went down 2 shims in size and got clearance, you most likely don't have a bent valve or it would be sticking open.  To check, remove the plugs and hold a finger tightly over the plug hole and crank it over.  If your finger is blown out with a loud pop, you don't have a bent valve.  You have compression.   

It's been my experience that the GS500 exhaust valves tend to recede into the seats and get tight.  Intakes do not.  With 80k miles on my 97 GS the intakes still had proper clearance with the original shims and the exhaust valve shims had been reduced several times till one was down to a min shim thickness. 
It's also been my experience that GS exhaust valves break rather than bend.      You really should fix that exhaust flange bolt though.

Thank you your post was very helpful. I did take the spark plugs out when I was trying this. I accidentally tried to start it with no spark plugs too and I noticed a puff of air, so I'm sure I have compression, guess it's not a bent valve but rather a really strong spring(?). I will try turning it with a 19mm wrench.

Here is a strange thing though. I reduced the exhaust intake by .01mm and now it won't start. It was much too tight before, yet it ran. Now it has the proper clearance and doesn't start. It sounds like something is getting stuck. What I mean is that the engine will turn over a few times then stop like something is blocking the engine from turning.

I want to put the 270 back in the exhaust but I don't want to put any stress on the engine.

When you changed the shim did you use the tool to depress the bucket or did you remove the cam?  If it's the latter you might have problems.  Is the cam chain tensioner installed properly?  Did you set the timing according the manual procedure?  You said the engine turns over a few times and stops so that might indicate a binding cam chain or improper timing sequence.  If you just used the depressor tool and didn't disturb the cams then disregard that stuff.

I used a depressor tool