exhaust valves not even close to fully closing

DogBunny

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Going over a newly-acquired old engine, it turns over freely, but the exhaust valves don't even come close to fully closing. I mean they need a good 1/8" more of travel to close.

Anyone have any thoughts on how both exhaust valves could be so far away from closing? They do go up and down. Intake valves seem okay.

All I could think of was crud on the shafts hanging then up, so I polished one shaft best I could wrapping long thin strips of Scotch-Brite around it and using back and forth motion, and using other methods, but no difference.
 
Can you pry up lightly on the valve springs just under the top retainer washer and get them to close up? If there's some carbon or rust built up on the stems, sometimes that will scrape it off. You may need to do it several times before they close on their own. If they keep hanging open every time you rotate the engine even after yanking them closed several times, maybe they're bent, although bending both like that would be rather odd. If you end up tearing it down, chuck the valves up in a cordless drill and spin them once you have them out. You'll see right away if they're bent.
 
Kathos, that was a good question. If someone screwed the tappets way too far in, that would prevent the valves from traveling all the way up and closing. But, that is not the case. I checked, and even if I were to completely remove the tappets the valves would still not close.

Airwolfie, I have not opened this engine, and my issue is not valve sealing, it is valve not even getting close to the seat. I need about 1/8" more valve rod travel before the valve face even contacts the valve seat.
 
Are the seats and valve faces clean of carbon? I've seen several engines with a lot of carbon stuck on the valve seats preventing the exhaust valves from closing. Then there is the possibility of a mis-timed cam having bent the valves........
 
5twins, sure enough, I pryed, and they closed a little. When I did my Scotch-Brite cleaning of the valve shaft, I think I must have cleaned the wrong end. Will work on cleaning them more tomorrow.
 
Yes, you need to clean the area in the port, between the guide and valve head. Maybe the little wire wheel on a Dremel will get in there.
 
gggGary, yes, everything is pretty gunky, looks like I will be cleaning the seats and faces too. I have gun bore cleaning supplies and the like for this purpose. Bent valves still a possibility too...
 
The carbon build-up can be quite extensive on an exhaust valve and stem, especially if the bike was run rich for a long time. Once out, I wire wheel them clean with a knotted brush in a 4 1/2" angle grinder .....

ExValveBacks.jpg


ExValveFronts.jpg


That carbon is really baked on there and while the angle grinder may sound like a bit much, that's what it takes. It knocks that stuff right off.
 
Well sure but that's where it came from too. Normal part of IC operation. It's just carbon if you don't use abrasives for cleaning. vacuum cleaner and compressed air in the plug hole will get rid of a lot of it.
 
Hang it upside down ??? You're talking about guys who don't want to take anything apart in the first place, lol.
 
Once out, I wire wheel them clean with a knotted brush in a 4 1/2" angle grinder .....

I think your secret for success is the tool not the method of turning it.
The regular single strand wire just can't offer enough resistance.
 
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