Started the 123 rebuild tonight!
 

Now that I'm back from my business trip I was able to start the rebuild of the 123. I know of 3 things that I had to do to start with. First, the fuel shut off was leaking if it wasn't completely open or completely closed. I removed the tank, took of the shut off and took it apart. I noticed that the little gasket, or o-ring, or whatever is in the little nut was cracked, the obvious reason why it is leaking. I found a new one on ebay for just $10 including shipping, so I'm going to replace the whole thing, since I'll get a new screen and all.

Next, the plug wire boot was ripped. I guess that isn't really major, but the plug wire is probably 40 years old, so I might as well find a replacement for it.

Finally, the muffler has a hole in it. This is where I need a lot of help. I removed the muffler fairly easily. After taking it off I immediately noticed stuff rattling around in it. I have pictures of the stuff that fell out, that I'll post, and a picture of the hole. So I have 2 parts to the question. Do you think the combination of the whole and the broken metal inside the muffler could have caused this knocking sound:

My YouTube video at 1m 16 seconds where you can really hear knock

And secondly, what should I replace the muffler with? Should I go with a used one/new one just like the old one? Or is there something quieter out there that would fit just as well, maybe even better. I'd like to have something smaller and quieter that dumps out on the left side of the tractor instead of going all the way across the engine. Or is there a specific design reason for the stock muffler? Please keep in mind that my goal is to improve this tractor, not restore for showing.

Here is the picture of the hole:

Attachment 5023

Here is a picture of the metal covered in carbon that fell out of the muffler:

Attachment 5024

Thanks for the help!

Dusty, your off to a good start. Looking forward to following your progress. I'll let the more seasoned guys give you the input on the muffler and the knocking sound.

I don't think you'll find a better muffler than the OEM one. Those pepperpot mufflers are not very quiet. That could have been your 'knocking' noise, but the only way to know for sure is run it with a different muffler on and see if the noise is gone.

Before you put that epay sediment bowl on, order a KOHLER bowl gasket for it. Those aftermarket bowls are made in Asia somewhere and the bowl gaskets don't seal at all. I don't think they're the right material.

Besides the noise, is it OK to run the engine without a muffler for a few minutes to see if the knock is still there?

pulse301 it won't hurt a thing. Just might make it a little harder to hear the knock.

Hmmmm...maybe I should always run it likme that and pretend the knock isn't there...haha. I will give it a try then just out of curiosity.

pulse301-

Just checked out your webpage. Very nice!

I watched the video, and I think that knock sounds like either an extremely worn front driveshaft coupler or the PTO clutch. If removing the muffler didn't remove the knock, remove the PTO clutch and try it again. Repeat for the driveshaft if necessary. That will hopefully tell you it's not something internal.

Thanks for the advice and checking out my page, Matt. The PTO clutch is already removed, the previous owner just handed it to me, haha. But it is very interesting you said it might be the driveshaft coupler. The drive shaft has a brand new bolt going through it, so it has obviously had something done to it recently. I will test out the muffler soon and if I still get the knock, I'll try the driveshaft.

There is not supposed to be a bolt there; it should be a hardened steel dowel pin. I imagine there's an L-shaped slot worn into the coupler on the flywheel. Most of them get that way after 40+ years.

Another thing that will do it is a worn out S/G 'basket' pulley on the crankshaft. Those rattle if they are loose on the crank, too.

I had a knocking sound on 1 of my 123s and it smoked a bit i pulled the motor, after taking the head off and checking everything out, so i new the motor needed to come off ! Well, I new all about the anti rattle springs, but i new that wasnt why mine was knocking! so I took the motor off, with it setting on the bench, I realized it was the anti rattle springs missing ! but if u dont have a pto on the front, proly not ur problem then !