Topic: valves are hitting...

[perrito]

Hey guys long time listener first time caller. How bad do these pics look? My buddies 76' motor locked up so I tore the top end down, this is what it looks like. Pistons ok to use? It looks like the underside of the head had a grinder taken to it just outside the valves??? I'm thinking new valves but any ideas how the valves would have hit the piston? Thanks.

http://i1305.photobucket.com/albums/s550/mamato23/Mobile%20Uploads/2015-04/IMG_20150406_161010_zpsvleztiuy.jpg

http://i1305.photobucket.com/albums/s550/mamato23/Mobile%20Uploads/2015-04/IMG_20150406_161058_zpssln59wx0.jpg

http://i1305.photobucket.com/albums/s550/mamato23/Mobile%20Uploads/2015-04/IMG_20150406_161118_zps3q4pli6f.jpg

http://i1305.photobucket.com/albums/s550/mamato23/Mobile%20Uploads/2015-04/IMG_20150406_161137_zpsxul2ltjs.jpg

http://i1305.photobucket.com/albums/s550/mamato23/Mobile%20Uploads/2015-04/IMG_20150406_161004_zpswczwyqtt.jpg

http://i1305.photobucket.com/albums/s550/mamato23/Mobile%20Uploads/2015-04/IMG_20150406_160949_zpskihixgjr.jpg

[oldhatt45]

perrito,

The third picture looks like the cylinder has cracked.
In another picture the head around the combustion chamber looks like it has been ground out past the point where it mates to the cylinder.
If these two things are true, I would personally question using either the head or the cylinders.

Charlie

[perrito]

That's the head gasket that makes it look cracked- it's def blown. Any info out there for what changes were made on different year heads?

[evanphi]

Hey guys long time listener first time caller. How bad do these pics look? My buddies 76' motor locked up so I tore the top end down, this is what it looks like. Pistons ok to use? It looks like the underside of the head had a grinder taken to it just outside the valves??? I'm thinking new valves but any ideas how the valves would have hit the piston? Thanks.

Made it easier

[SOHC4 Cafe Racer Fan]

The surface of the head looks awful. Can it be fixed by decking it?

[mystic_1]

My buddies 76' motor locked up

Tell us more about the motor locking up.

Valves hitting the pistons would have to mean a pretty serious issue in a stock motor.  You'd have to have a severely worn cam chain and tensioner, or have it jump a tooth (which I've never heard of happening) or something similar.

mystic_1

[Vinhead1957]

Valve job at least,  the valves need to be checked for straightness.  What caused it? Timing!  The chain was either too sloppy and jumped a tooth or set up improperly.   

[perrito]

Thanks for the replies guys- here's what it is: My buddy bought the bike not running about a year ago, the seller said it ran great but needed carb work (don't they all...) I had a look and tweaked the carbs and it fired up and sounded great- he rode it away but a few hours later he said it was stalling while taking off ( letting out the clutch) we brought it back and I pulled the clutch- wasn't too bad it had a couple broken fiber plates but I replaced and put it back together- same issue. I was rolling it over with a socket wrench to line up the timing mark and it locked up, so not when it was running. I pulled the head and that's what you see. The surface area around the valves looks terrible, i'm just looking for ideas on what to do next. I figured new valves seals etc, it's not much to do pistons from here on. anyone have a decent head for sale??? Thanks for fixing the pics- some sites only like to use the links.

[Airborne 82nd]

http://forums.sohc4.net/index.php/board,174.0.html

http://forums.sohc4.net/index.php/board,176.0.html

Try here.

[mystic_1]

What is the state of the cam chain and tensioner assembly?  You need to find the root cause of the interference problem.  The rubber rollers on the tensioner, especially the big one, tend to go bad in a pretty serious way.  Also check for badly worn cam sprocket teeth.

Also, is the cam stock?  It's pretty quick to measure base circle and lobe height, your manual will have the stock specs.

I'd guess this motor was overheating maybe, from the state of the head gasket?  I believe repeated extreme heat cycles can make them go out-of-round line that.

I think there's a good chance that the grinder marks you're seeing are from the factory.  Line workers apparently did hand cleanup work on the castings and they didnt always do a great job.

mystic_1

[perrito]

I haven't pulled the jugs yet but I'm thinking that new pistons is the way to go, i'll check he cam chain tensioner then. I don't know about the cam yet, haven't measured it. I know nothing about this bike- it's a chop but it looks like the guy that built it did a decent job. Interesting comment about the grinding marks. Any idea of the year of the head? the only marks I can find are an X3 and whatever is in this pic:
http://i1305.photobucket.com/albums/s550/mamato23/Screenshot_2015-04-08-10-39-42_zpsdyrljiie.png

[mystic_1]

New pistons do seem like the way to go. 

No way to be 100% sure of the exact year of your head but the sealing rubbers between the cylinders and head, plus the domed pistons, suggest an F model engine or a 77/78 model engine I believe.  Barring other evidence there's no reason to believe so far that the head doesn't match whatever the engine number indicates.

I assume this is the chopper in question?  Is that an Santee frame?  I see one of the Santee electrical system boxes tucked in under the carbs there.



mystic_1

[perrito]

Thanks Mystic, that's not the bike in question, although I did go through a lot of the same issues, that was my first build. The frame isn't santee and I had a lot of opinions about where it came from- the closest I could tell was GME-probably a custom job. Before I got it someone dropped a battery bolt in the tank and it made it's way through the motor and lodged between the head and one of the valves. The motor #'s on the one i'm looking at show it to be a 76'.

[Old Scrambler]

Bolt got from tank to head..................must have been a huge petcock and garden hose feeding a Holly

Those swirl marks on the head look like its already been shaved..........and poorly ............its cut into the valve seat material.

Compare it to a stock K or F0-1 head and proceed. Tell us about the cam profile. 

[perrito]

EDIT:I think it was dropped into the oil tank not the gas tank.... I rode it for a couple years before it finally locked up on me.