Flathead stuck valve

[ElekVins]

Went for a ride the other day on my UL, I did about 150 miles with a coffee stop in the middle.
Engine worked great.
But suddently I lost power and the engine was on 1 cylinder.

It looks like I have a stuck valve (exhaust rear cylinder)
I didn't open the top end yet, just noticed that valve doesn't go down as it should.

Any idea why this happens?
What are my options at this point?
Doing a complete valve job (and top end?) is mandatory or there are alternative ways to "unstuck" that valve?

[Hubbard]

excess carbon binding, valve stem galling, or too little clearance when installed. once you have the head off put some penetrating oil on the valve stem and wait a bit. if you can get the valve out you'll find out what happened. mite have to put a thick feeler gage on the tappet to push it up a wee bit to get the oil working.

[DustyDave]

Or somebody using guides other than high silicone cast iron. Never dealt wit a Hardly flatty but an Indian that is parade ridden needs a tiny hole drilled in the breather disk so that there is enough oil mist left in the engine for the guides n stems at extended near idle use. or any air leak between the crank case and the valve. Oil mist is really hard to get up an exhaust stem with the exhaust gas pushing down.
Is it staying open (stuck valves stay open) your pic looks like the stem is close to the pushrod. If it isn't moving up and down as much as the other exhaust and has normal clearance when closed you need to look in the cam chest. If it's hard stuck the valve will stay wide open, if partially stuck it will go up and hang and then return slowly or snap down. If it's stuck pulling the top and doing it right would be the better option. They have gotten too valuable to Band-Aid.
Dusty

[ElekVins]

I guess opening the top end is next, to find out more...
If I don't see anything weird then outside from the stuck valve, I'm tempted to attempt of making it move again.
Doesn't mean I wont do a valve job next, but just out of curiosity, if it was enough?
I don't have "penetrating oil" on my shelf, would WD40 be stupid?
I can sure order some oil no doubt, but if WD40 is fine...

[DoomBuggy]

WD40 = Water Displacer not the same as a good penetrating oil.

[confab]

Following with interest..

What causes this?

Tolerances too tight and galling? Or clearances too loose and burned carbon fouling the guide area?

[JBinNC]

Following with interest..

What causes this?

Tolerances too tight and galling? Or clearances too loose and burned carbon fouling the guide area?

Almost always a vacuum leak causing the motor to run a little lean and overheat the exhaust valves. Hot exhaust valve galls the stem and guide, and stuck.

Jim

[Dragstews]

Bingo .. ^^

[JBinNC]

^^^^

Seen a few?

^^^^^

Jim

[ElekVins]

WD40 = Water Displacer not the same as a good penetrating oil.

Got that! will get the appropriate.
Is there any difference between penetrating oil and penetrating grease ?

Found this:
(Think it will do the job but just want to make sure)

[DoomBuggy]

To be honest I have never heard of penetrating grease before.

[confab]

Something we use for polishing deep passages in valve bodies is a wire hone.. It is basically a piece of coat hanger bent over flat at the end, with a few wraps of 1200 grit sandpaper around it. Chuck it up in an electric drill.

You run it wet with mineral spirits, or brake cleaner or whatever.

If you're just absolutely gonna run this, wouldn't removing the valve and polishing out the guide a little be the way to go?

If you had a way to chuck the valve up and work on it too, that couldn't hurt..

Be a pretty quick thing to do. Probably even re-use copper head gaskets?

???

[ElekVins]

Almost always a vacuum leak causing the motor to run a little lean and overheat the exhaust valves. Hot exhaust valve galls the stem and guide, and stuck.

Jim

I have the feeling I didn't have any intake leak, mounted new Peek seals recently. But also I changed the carb not long ago for a Dell'Orto and I have to admit I wasn't as rich as I wanted, I believe it was ok but a little too lean...

Could that be the reason?

Also it was the first time I did a 150 miles ride with this carb, but I did a 45mn stop in the middle so I assume the engine wasn't hot like if I did 150 in a row. Did several 50 to 75 miles ride before with that carb

[Hubbard]

what was wrong with the linkert?

[ElekVins]

what was wrong with the linkert?

not sure what was wrong with it, tried to tune it for a long time but the bike never ran great with it, maybe it was too worn out (?) suddenly when I put the dell'orto all went way better

Linkerts seems very simple to tune, I read a bit about them but it seems I'm not lucky with them, not sure why.