Potential valve damage?

[p00tster]

I picked up a non-running 1981 XS400 Special. Long story short, the motor spun freely and the starter would spin the motor, but it refused to start. After digging into it, I found that the exhaust valve adjustment screw and locknut had completely fallen out of the rocker arm for the left cylinder.

Luckily, both were sitting there by the valve so I was able to fish those out, but then also found that the rocker arm threads were stripped. I now have the cylinder head off and the defective rocker arm removed with a new one on the way.

My question is could there be damage to the valve face since the adjustment screw wasn't even present?

 

[spectra]

I picked up a non-running 1981 XS400 Special. Long story short, the motor spun freely and the starter would spin the motor, but it refused to start. After digging into it, I found that the exhaust valve adjustment screw and locknut had completely fallen out of the rocker arm for the left cylinder.

Luckily, both were sitting there by the valve so I was able to fish those out, but then also found that the rocker arm threads were stripped. I now have the cylinder head off and the defective rocker arm removed with a new one on the way.

My question is could there be damage to the valve face since the adjustment screw wasn't even present?

My thought would be no as the motor never ran for you. Also the valve face would have had to come in contact with the piston and if it wasn't moving I think that would be hard to have happen. Just my thoughts and I am by no means an expert

 

[Jeff0133]

Take the valves out and inspect/measure them...there could be unseen damage like a slight bend in the stem which can lead to real damage down the road.

 

[p00tster]

Update: I wound up replacing the rocker arm and dropped the head back on. Did my first valve adjustment on the left cylinder, but as soon as I went to adjust the right cylinder, I couldn't get the crankshaft to fully rotate. Wound up taking off the head, again, and inspected the timing.

The alignment mark on the camshaft is sitting at about 10:30 when it should be sitting at 12 o'clock at TDC (I also made sure the LT mark was accurate on the rotor by dropping a straw down the spark plug hole to make sure the left piston was sitting at the top of the stroke).

It looks like I need to reset the position of the cam in relation to the rotor. Is it just a simple matter of removing the timing chain guides to give me enough slack to lift up the timing chain off the sprocket?

 

[BBS360]

The sprocket unbolts from the camshaft.
Pull it away and you'll have plenty of slack to align LT, timing mark, and camshaft.
Make sure the horizontal marks on the sprocket are totally in-line with the head surface.

The section in the Haynes manual covers it pretty well.

 

[p00tster]

I got everything timed correctly. Unfortunately, on the first attempt to start up the motor, the timing chain broke. It's likely that at least one valve is bent.

I'm going to pull the head to inspect (and likely replace) the valves, but I'll also now need to replace the timing chain. Is it possible to install the timing chain through the center ported area on the bottom sprocket (i.e. dropping in down through the top of the jug), or does the case need to be split to get to it?

I looked through the manual and couldn't tell unless I missed something.

 

[BBS360]

No need to split the case. It'd be a hell of a lot easier with the jugs off but you should be able to do it with them on.
I'd get a piece of wire that you can bend into a hook to thread around the crankshaft. Then pull the chain through with it.

 

[p00tster]

I got the head off last night. Thanks for confirming that I can install the new timing chain without splitting the case - I can see now that I've got enough room to work with by installing it through the "valley".

One other question: does anyone know if a cylinder head from a 1980 model will fit a 1981?

I ask because I have two valves that are bent, plus two of the valve covers had rounded hex heads that need to be replaced. I could actually save money buying a used head with valves rather than trying to purchase 2 new valves + valve covers.

I checked the parts catalog and the part numbers are different for the cylinder head assembly between an 80 and 81, but that doesn't always mean they aren't compatible. Looking at pictures, they look identical.

Has anyone done this swap?