Potential Valve Tapping When Warm?

1982 Yamaha XJ650L Seca Turbo

Greetings all. I acquired this bike a year ago and have had to do a handful of things to get it back up to snuff again. As follows:

- Rebuilt turbocharger from XJ4ever
- New BP8ES NON-resistive spark plugs
- New fuel pump (Carter)
- Wix inline fuel filter
- Valve shim clearance check, and replacement of following shims as if facing the engine from top-down (underlined and bold indicates shim that was replaced due to being too tight):

EXHAUST

1 2 3 4

INTAKE

1 2 3 4
​

Exhaust valve 2 was .15mm. 2.70mm shim brought it to .20mm. A little wide but exhaust 1 and 4 also measured .20mm. Intake 1 was .10mm, 280 shim brought clearance to .15mm Intake 3 was .9mm, 280 shim brought clearance to .14mm. All fine and well, except ONE thing, which I will elaborate on in just a moment.

- Carburetor cleaning; complete removal and disassembly of carb rack and all carb parts, MINUS the throttle shaft seals (I know. I couldn't bring myself to attempt removal for fear of gouging the venturi of my carbs trying to grind away the stamped back-side of the throttle plate screws, then stripping the screw heads, and damaging new seals trying to install them.) Carb parts replaced:

• All pilot jets
• All float bowl gaskets
• One enrichment circuit plunger
• All hat screws
• All top and bottom rack screws
• All enrichment plunger SHAFT screws
• All between-carb vent tub o rings
• All fuel supply tube o-rings

Every hole, orifice, and jet in those carbs was sprayed with carb cleaner until there was fluid coming out another side of the carb. (There was 1 air jet-looking orifice on inlet side of each carb that actually just proved to be a dead end.)

- All carburetors bench synced, then vacuum synced while on the bike, while using YICS eliminator tool from XJ4ever. (No colortune, pilot screws set 3 turns out)
- New foam air filter core from XJ4ever
- New alternator brushes, cleaned inside alternator cover and rotor surface
- All fuses replaced with inline fuses.

I think that's it that I can recall. Now, what I said I would elaborate on earlier. I had a bit of a situation with the exhaust 2 valve shim trying to install the new one. Got the old shim out successfully, and when I installed the new one, there was a gap between the shim and the bucket, as if the new shim were slightly smaller in diameter than the old one. This was from a viewing angle that didn't reveal the whole "picture", if you will.

I thought that was odd, but decided to go ahead and try to rotate the cam away so I could remove the shim tool. Upon removal of the tool I then went to turn the engine again so I could try and do a full rotation. The lobe began to press into the shim, then the my wrench came to a DEAD STOP. I backed off, and gently tried again. Same thing. I then went to glance at the shim, and it was no longer in the bucket. It was never fully seated, and the lobe pushed it out. The angle the shim ended up at basically became a "brick wall" for the cam lobe which stopped me from turning the motor. Once I figured this out I managed to get the shim removed, although nearly loosing my sanity.

Looking at the shim now, at certain angles a mark was visible on the shim where the lobe pushed against the shim. The shim did not appear bent, and running my fingernail over the mark still felt smooth. I ended up reinstalling the shim, asked Len about it and it was hard for him to tell through an image and not being there but he seemed to think it'd be fine. The bike is completely put back together and running EXTREMELY well, minus my battery being weak. EXCEPT, when fully warmed up, one valve seems to be noticeably louder than the rest. The ticking sound seems to be coming from the left side of the motor...the side where the pesty exhaust valve is whose shim, with my help of course, nearly sent my cylinder head to its grave.

With all this in mind. How certain can I be this shim is the cause of the noise? Maybe it's gouged enough to make noise? Maybe it's bent? The shim seemed fine even after the incident, minus being able to visually see that mark. I cannot recall this sound being there before doing shims. Maybe I accidentally tightened the cam chain when turning the engine backwards and forwards while doing the shims? There was 0 slack in it I remember, seemed quite tight. Any input is appreciated. Like I said, the bike runs and performs quite well, that noise when warm just concerns me. I've read some other threads where folks have mentioned tapping on an air cooled head is good, which is comforting, but this sound seems to stand out from the rest of the valve train. At least to my untrained ears. Sorry for the long post.

 

Check that your exhaust pipe is tight. You can get ticking sounds from that but it seems you would also hear it when not fully warmed up.

 

Is the ticking noise a loose exhaust header pipe?

 

I totally neglected to mention that I did examine that as a possibility as I read it on another thread. I did go ahead and ensure all my headers were good and tight. Of course, I could do it again, but doing it the first time didn’t seem to change anything

 

The exhaust gaskets may be too thin to be effective now. See if you can detect any leakage. Hang a small feather near the junction to see if it moves around, or try puffing something like fine baby powder/talc in the area to detect a leak.

 

I do have a lighter I can hold up to the exhaust header junctions with the head…?

 

What @Huntchuks is saying is the feather or talc would puff or flutter away from a header leak in the breeze of the leaking exhaust. When messing with the exhaust studs be gentle. If too heavy handed they break easily and are REALLY miserable to repair.

 

Gotcha. Well, I didn’t have a feather around at the time but I did use the lighter…when everything was warm and the noise showed itself I checked around the headers. Seems that the flame would flutter a bit between joints 1-2. I thought I was onto something, as that is the side the sound is most noticeable on. But it did the pretty much the same between 3-4. Maybe they’re all leaking. I might have to try again when it’s cold.

 

Any welding gloves, you can push the headers against the exhaust ports to see if it is quieter, or use a shop towel or something similar. If you need to replace the gaskets spray something on the threads of the exhaust studs (overnight preferably) as Fuller stated they break easily especially if as usual the are corroded with all the dirt and water that side of the motor gets.

 

This is how NOT to extract a broken exhaust stud

 

No welding gloves…I found a 2x4 however, used it to push against my exhaust headers with it warm and idling and it didn’t seem to change much, if anything at all.

 

That is…a little scary

 

Ahhhh, now I understand what you were doing with the lighter. Yep, that should work too. Did it flutter toward the head or away from the head?

 

I would say more away. Maybe to one side a little, like away from the center of the motor.

I did also use a 2ft long hollow steel rod to try and listen and see where the sound may be loudest. Still seems most intense from the left side of the motor but holding it near the header joints and then up towards the spark plugs didn’t really seem conclusive.

 

As an update, I swapped the two exhaust headers on the side of the motor where the sound is coming from. I thought that maybe when I reinstalled them after having them off a few weeks ago (long story), that I installed those 2 incorrectly. Swapping them seems to have made no difference. I thought maybe it took longer for the noise to show itself, but I don’t really know.

 

Not sure if this would be possible but...
Loose valve shim? maybe excessive clearance involved? Really thin oil from being hot?

One of my bikes used to do this on a really hot day, but it kinda went away so I never got to the bottom of it. Above was what I was thinking after all the header investigation.

 

I was wandering about excessive clearance myself. Running a fresh change of Valvoline conventional 20w-50 4 stroke motorcycle oil. The exhaust valve shim I had trouble with ended up measuring at .20mm after I got it in. Wide, but still within clearance. What is getting to me is that I don’t recall hearing this “tapping” noise before checking and replacing those valve shims. Aside from bringing tolerances back within spec, I can’t for the life of me think what else has changed to potentially cause this noise.

From the reading I’ve done on here, it seems that these heads should have more audible valvetrain due to being air cooled, which I do normally hear. But this sound really seems to stand out from the rest of the sewing machine noise, on the left side of the motor and only at FULL operating temperature, like after riding for a few minutes.

 

Ahh. What you said in your original post!
I know those shims are like a suction cup on glass when in the bucket... But a small deviation may prevent that being true.

Pop the cover and see if it moves easily without the lobe pushing it.