GS650L - Intake valve not seating

[DaveP]

I have had this 1981 GS650L for a couple of years now tinkering with the engine and bringing things up to spec. I am now having an issue with the #3 intake valve.

When I got the bike, valve clearance on this valve was 0.05mm which I adjusted to 0.10 mm. The bike was running well until it suddenly wasn't. I have rechecked all of the valve clearances and they have stayed as previously measured except for the #3 intake valve. This valve is now 0.24mm which is in agreement with the loss of compression in this cylinder. I tries to send a camera through the spark plug hole, but could not get a good look at the valve.

Hand cranking the engine to move the valves, it it is very difficult to rotate the engine as the #3 intake cam starts to engage the valve.

Is it time to tear down the engine?

 

[JTGS850GL]

So, if you adjust the valve to back in spec, does the compression go up? If you add oil to that cylinder, does the compression go up? What tool did you use to do the valve adjustment originally? Did you use the zip tie method? If so, you may have had some carbon debris left over from the adjustment that threw the measurement off.

 

[Big T]

Dave,

I believe you are saying the valve does not come all of the way back up now


If it's stuck like that, it's time to take the head off

I take it you did not see any other items that shouldn't be there when you looked in the cylinder?

 

[DaveP]

Yes, the valve does not appear to be coming back up all the way. Top of the piston looked fine and nothing inside the cylinder.

 

[tom203]

Maybe the bucket is stuck somehow (debris?)- rotate cam lobe away from it and see if you can fiddle bucket up and down.
Seems odd that it was running ok and then......

 

[DaveP]

The bucket spins freely and can push it down easily with the bucket depressor tool, but does not help restore the proper valve clearance.