Valve issue help (video)

[AntonLargiader]

Looking at the exhaust valve pocket in the piston, is there some damage to the edge?

EDIT I realize it's the intake that's loose... just wanted to see if there was a bigger problem happening. In the photo of the valves, it looks like the intake isn't fully closed. Is that correct? Can you take a side pic of the closed valve?

View attachment 77532

 

[brook.reams]

I did notice that the intake valve sits slightly lower into the cap than the exhaust valve does. I thought maybe this was my issue but I pulled the valve cover on the opposite cylinder and it appears to be the same, and without a gap. Can anyone confirm that this is correct? And again, the valve is seated inside of the cylinder head.


Hi Chris,

From your description, something broke. The question is, What?

Here are some things you can do to try and locate the failure.

1. Drop the oil pan and look for any fragments in the bottom. This is easy to do. Any shrapnel found will help identify the failed component.
2. Remove the valves and springs. Verify the springs are not broken. Verify the valve seats are not loose in the head.
3. The push rods are a composite assembly of two steel ball ends in an aluminum shank. Check that the steel ball ends of the push rods are not loose in the shank of the push rod. It one is it will clank and rattle and you need a new push rod.
4. Verify that a cam lobe is not broken, or chipped. This requires visual inspection of the cam which can be done with the cylinder off the bike. You do NOT need to remove the piston from the cylinder to do this, and in fact it is better if you don't. Just remove the wrist pin and slide the left cylinder off the cylinder rod studs with the piston and rings captive inside the cylinder.
5. Then pull the cam followers out. Check if the side of the follower where the oval hole is has gotten cracked. While you are there, also verify that the face of the follower that rides on the cam lobe shines like a mirror and there are no pits on the face. Pits aren't the cause of the sound you heard, but if the followers are pitted, you need new followers and likely a new cam.

I hope this is helpful to you in identifying what is broken.

Best.
Brook Reams.

 

[69zeff65]

Remove the intake valve and inspect the seat

Before you pull the cylinder or drop the pan I would suggest inspecting the valve seat with the valve removed. That is a quick and fairly easy way to rule out a valve seat getting loose and dropping out a bit. That "snap" you heard may have been the loose valve seat partially resetting back into its pocket with the spring tension. Most auto parts store provide free tool use with a deposit so if you don't have a valve spring compressor you can probably use a loaner. You should also take a look at the throttle butterfly in that carb to make sure both screws are in place.

All the other suggestions are great so long as you thoroughly inspect each suspected component before going deeper into the motor.

 

[pauls1150]

Maybe it's just the lighting in the pictures, but have you been able to verify that the valve collets ("keepers") are all there and whole?

 

[m_stock10506]

Chris, did you do any work on the valves recently?

I had a situation once where a valve adjuster lock nut got loose shortly after I did a valve clearance adjustment. I got about 5 miles from the garage and the motor was making quite a clatter. I had about the same kind of clearance that you showed in the video, but the lock nut was loose when I removed the cover to see what was wrong. Was your lock nut still tight, or was it loose? Of course that still would not explain the snap that you heard.

 

[69zeff65]

Excellent observation

Maybe it's just the lighting in the pictures, but have you been able to verify that the valve collets ("keepers") are all there and whole?

If you compare the visible valve stem above where the keepers are it appears as though the exhaust valve has about an 1/8" more valve stem showing above the keepers than the intake valve. Maybe the "snap" was a keeper (collet) popping out

 

[ebeeby]

If you compare the visible valve stem above where the keepers are it appears as though the exhaust valve has about an 1/8" more valve stem showing above the keepers than the intake valve. Maybe the "snap" was a keeper (collet) popping out

I agree with this. Looks like something happened to that collet compared to the others.

 

[AntonLargiader]

The collet would only affect spring height, not valve stem position. The valve stem height is determined by where the valve closes, and I think this is the problem. Likely a dropped seat, as mentioned before. Again, a good pic of that area would help.

 

[barryg]

The only way to get a good pic is the disassembly of the head and the head and components completely cleaned for examination.

 

[PoorUB]

The collet would only affect spring height, not valve stem position. The valve stem height is determined by where the valve closes, and I think this is the problem. Likely a dropped seat, as mentioned before. Again, a good pic of that area would help.

Correct! The spring and related hardware have nothing to do with valve clearance. At this point with the head off I would pull the valve and check the seat to make sure it is in the counter bore when it belongs.

 

[Na Cl K9]

One last observation: the pushrod is not centered in the pushrod tube as it exits the head under the adjuster on the affected rocker. The other one is centered as it should be. Nothing about the combustion chamber looks off. An earlier post mentioned lifters so I’d go there next.

 

[cycleman2]

Looks like you need to take the intake valve out as it does look like it is sitting a bit proud. Anything come loose from the front of the carb, like one of the throttle butterfly screws. It does appear as if something might have jammed the valve partially open. A piece of carbon could do the same. Shine a light inside the intake of the head and look at the point where the valve contacts the head. If you see some daylight between the two you found your issue.

It is common for carbon to build up on the back of the exhaust valve but not the intake. But anything is possible.