Valve clearance became excessive out of nowhere.

JE4570

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So my valve clearance became extremely excessive all of a sudden. The weird part is my bike ran fine before. I had taken it on its maiden voyage since my second time in the engine earlier this spring (~70-100 miles) and one thing I noticed was that the cam chain appeared to have gotten a bit on the loose side by the end and began to make a small amount of noise but nothing too worrisome sounding. When I got it back I tightened up the cam chain and left it to sit for a while (I got busy) and have even started it occasionally just to make sure that gas was flowing through the carbs. It ran fine every time.

Today I replaced my old fuse box with a bunch of in-line blade fuses and went to start it to check my work and could not get it started properly. The right side would fire and run but the left side exhaust stayed cold so I assumed I got it running on one cylinder but it made a horrible clacking noise. I check the compression and it was not there on the left side so that led me to check the valve clearances and found that at top dead center my left exhaust valve had extremely excessive play (like 2-3 mm). Now when I’m trying to reset the valve clearance on my left exhaust, it almost is as if the screw is not long enough to get the proper clearance. It can achieve the proper clearance but the locking nut has a little bit that isn't threading over the whole screw. (See picture)

190260BD-4190-43BD-B384-123E4DF73CB6.jpeg

*this is a rough estimate of the clearance. I have not set it yet.

Could my adjusting of the cam chain have messed my valve timing? Another question would be did I skip a tooth? I feel like I was never running too loose... if anything probably more on the too tight side after I had re-tightened the chain.

I think my next steps will be to reset everything from ground zero and see if it will start again because I’m guessing if I somehow skipped a tooth it probably won’t start until I fix that.
 

JE4570

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Update: I just reset the left side clearances properly and get zero compression on my left side. Where could I be losing my compression?

my right side is at 120...
 

Jim

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Update: I just reset the left side clearances properly and get zero compression on my left side. Where could I be losing my compression?

my right side is at 120...
I'd suspect your exhaust valve is stuck (partially) open That would explain no compression and the wonky adjustment.
 

JE4570

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I'd suspect your exhaust valve is stuck (partially) open That would explain no compression and the wonky adjustment.

you are probably right because my intake clearance was still fine I will investigate and see if it’s something I can fix.... What would cause a stuck valve? Are there methods I can do without taking the engine back down?
 

Jim

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What would cause a stuck valve?
Usually from carbon buildup or corrosion... but since you were recently in the engine I'm assuming that it was all cleaned up? After that, most likely a bent valve. Is the valve original?
 

JE4570

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Is the valve original

Yep... looks like I might be doing some more work.

My engine was running a little bit on the rich side but I don’t think it would have developed enough carbon buildup in such a short time to cause this. I definitely cleaned up my valves when I had them out.
 

Jim

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In the Lycoming manual there's an approved procedure called "staking the valve." Used to break up corrosion and carbon buildup. What you do is set a piece of wood on the rocker arm and smack it real good with a hammer a half dozen times or so. If you try it, back your adjuster off first and make sure your piston is at BDC. If that don't re-seat it, you'll be opening the engine back up I suspect.
 

JE4570

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In the Lycoming manual there's an approved procedure called "staking the valve." Used to break up corrosion and carbon buildup. What you do is set a piece of wood on the rocker arm and smack it real good with a hammer a half dozen times or so. If you try it, back your adjuster off first and make sure your piston is at BDC. If that don't re-seat it, you'll be opening the engine back up I suspect.

I will give this a try. Anything that’s easy and free is always worth a try.
 

Jim

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I'll emphasize again.... make sure you don't smack the valve into the piston. :yikes: You want BDC or thereabouts,,, just starting up on the compression stroke.
and make sure the adjuster's backed off or the valve won't have room to re-seat.
 

Jim

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Just a thought.... it'd be pretty easy to pull the exhaust header and see what's up with the valve.
 

JE4570

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Is it too soon to ask what happened?
:whistle:
Man, its been a while since I have been on here! It was a stuck valve, however I have yet to open it back up to see if it was bent or what not… I got busy with life and working and all that, but I think I will plan another rebuild when it warms up and try to do it right this time. I’ll have new valves and valve guides installed and have a machine shop do that work.
 
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