bigedmustafa

My Feedback: (2)

Last fall I had a less-than-graceful landing with my very graceful Ace Staudacher S-300. The muffler of my Thunder Tiger F-91s smacked the asphalt runway, and it resulted in a broken exhaust fitting on the cylinder head where the exhaust pipe screws in.

Paul's Model Supply promptly delivered a new cylinder head for me, and disassembling the engine was very simple and straighforward, right up until I got the cylinder head off and all of the other components removed except for the inlet and exhaust valve assemblies with valve spring set, spring retainer set, and spring hold collars.

I have no idea how to remove the spring hold collars and spring retainers so I can transfer the valves and springs to the new cylinder head. Does anybody out there have any experience removing a similar kind of assembly from another glow engine? I've noticed that Thunder Tiger offers the cylinder head available with the valve assembly, I'm hoping it's not because changing the valve assembly over is going to be a huge pain.

You can see the owner's manual here: http://www.acehobby.com/ace/PDF/Engine/F_91s.pdf The parts diagram is pg. 14 and parts list is pg. 15

Thanks in advance for any help or suggestions!

bigedmustafa

My Feedback: (2)

The spring hold collars are pressure fit underneath the spring retainers. Getting them off was rather easy once I compressed the spring, but getting the spring retainer back over the spring hold collars is really challenging! I've tried simply snapping the spring retainer on over the spring hold collars without the spring in the way, and it seems impossible to do by hand.

It's really amazing that such small parts can be so incredibly stubborn. I wouldn't even believe they fit together like they're supposed to if I hadn't taken them apart myself. Fortunately I only removed the exhaust valve from the old cylinder head so far so I can't get parts mixed up.

I'd love some advice on how best to reassemble the valve springs onto the new cylinder head. Had I known how tough this was going to be, I'd have happily shelled out $20 extra for a cylinder head with valve spring assembly already included!

Iflyglow

My Feedback: (79)

Make sure you do it inside of a plastic bag, or you will lose the little stem keepers for good.[X(]

bigedmustafa

My Feedback: (2)

I set this little chore aside for a while, but tonight I finished it up. I used a small metal fork to depress the valve spring and spring hold collar while my wife put the spring retainers on for me. It was a two-person job, I don't think I ever could have done it alone!

Iflyglow

My Feedback: (79)

I have done it on a few Saito's, and it can be real pain by yourself. I did it inside of the bag like I mentioned.