[The Garbone]

On the missing lash cap, there is not guarantee if it was ever there to start with. 

The rocker looks fine from here.  I would pull it and check for freedom of movement before ordering one.   

I would also pull the push rod and roll it on a table to insure it is not bent (if it is replace it) and then put it all together, re-adjust to push rod an make sure the lock nut is tight.  The lock nut may have come loose, rod shortened and the jumped out.  That may be your problem.   If the rod is straight, adjuster tight and you can't adjust it properly you may have a dropped seat. 

Can you feel compression when you kick the bike through with the push rods out?  If you have none the exhaust valve is probably stuck open due to the seat. This can be verified as a last resort by pulling the head and having a look.

Call Nfield gear with ye olde telephone and they can get you new rocker gaskets and a lash cap.  The online store is just pretty but very incomplete.  If you do indeed need a rocker arm and block I have a spare set in my garage and can send you one.

[chukzelda]

Garbone,

Ok, I lengthened the pushrod (really easy to do when it's pulled out) so it was flush with the rocker arm at top dead center.  I put everything back together and tried to start the bike.

Bike had a hard time starting.  Felt like compression loss somewhere.  The bike did start, had a hard time idling and there was a clanking sound coming from the rocker arm.  Shut it right down.

I'll pull it apart again but need you to explain how to check if the exhaust valve is stuck open (please?).

peace,
Chuk

[The Garbone]

About that clunk.  Remove the plug and kick it through with the rockers together but the cover off.  Can you feel clunk feedback through the kicker when moving it through he exhaust stroke?  If so the clunk may be the piston hitting the valve and forcing it closed, but with the valve seat loose it is holding the valve open a hair killing compression.  Watch the rocker, valve and push rod as you push it through real slow and maybe you can determine what is hanging up. 

If the push rods are adjusted per the manual its sounding like the seat.  Exhaust valves are the ones to go as they are on the hot side of the head.

[Arizoni]

The Nfieldgear catalog shows several different rocker arm assemblies that fit the Iron Barrel engine.  Notice I said assemblies because they include the upper and lower blocks that the rocker arm runs in.  They are also sold only as sets so they will include both the exhaust and the intake valve rockers along with the blocks they run in.
(As a side bonus, replacing those blocks may quiet your engines valve noise too.)

Now, before jumping on the bandwagon first you need to study both the exhaust and the intake valve rocker arms where they would contact the valve stem "lash cap" as Ice calls it (find no 18 in the exploded drawing) carefully.

Bear in mind I haven't been into a Iron Barrel engine so when I mentioned a hardened piece attached to the rocker arm it was an engineering based guess.

The pictures in the Nfieldgear catalog seem to reinforce it because there appears to be a circular disk on the ones shown in the catalog but that may be my mind wanting to see something there.

Anyway, you need to see if both of the rocker arms look exactly the same where they would contact the valve lash caps.
If they both look exactly the same you probably do not need to buy new rocker arm assemblies.

If one has a little hardened button and the other one doesn't you will need new rocker arm assemblies.

The rocker arm assemblies shown in the catalog are available as  "Premium Aluminum Alloy Rocker Block Assemblies" ($64.95) or, "High Performance Rocker Assemblies" with steel blocks ($99.95), or "Ultimate Steel High Performance Rockers" with steel blocks ($84.95).  (Note: the catalog I have is over a year old so the prices may have changed).

These rocker arm assemblies will NOT fit the AVL models so you should call the folks at Nfieldgear at 1-800-358-0938 and tell them exactly what your engines serial numbers are and exactly what your problem is.  They should have the new gaskets you need too while your on the  phone.

Getting back to your valves:
If the rocker arms look exactly alike where they contact the valve stem the "lash cap" may be missing.
Both valves should have this cap so look at the ends of both valve stems.  You do not have to take the valve springs off to see them as they are right on top.
Again, both valves should have the caps and they should look exactly the same.
If one valve stem looks smaller and different the cap is missing.

I don't see these caps offered in the catalog but when you call Nfieldgear they should be able to sell you one.

If the rocker arms are the same and both valves have their stem caps you don't need to buy anything.  The push rod may have been too loose and jumped out of position.

Note:  This was being written while some other posts were made.