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Discussion Starter #1
I re-oiled the felt washers on the throttle shafts on my Keihin 722a carburetors and after putting them on I noticed a small gap on the outer portion of the shaft where the nylon spacer slides a little instead of being flush. I'm not sure if it was like this before or not and was hoping someone on here knew. It's a 1972 CB350 twin.

carb1.jpg

carb2.jpg

carb3.jpg
 

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Did you change the felts? After 43 years they are shot. Here are a couple of shots on my 450. There are more details on my build log.
IMG_0687.JPG
IMG_0686.JPG
 

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Discussion Starter #3
I didn't change them but by your picture I need to because mine are not even half the thickness of yours. That would explain the extra slack on the shaft. Thanks a ton! Where can i source them?
 

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Your seals look like mine did. I got a sheet of .125 felt from mcmaster.Com and cut them using a Harbour Frieght punch set. 1/4 ID, 1/2 inch OD. I'm not sure what the thickness of the stock seals were, but mine are thicker. On the throttle cable side of the carb, I had to flip the metal retainer over. If you have an old cowboy hat that could use a few more holes in it, that would work. It was a bit of a pain to make them. It took about 15 tries to get about 8 good ones. If you can wait until next week I may have time to cut some more. Send me a PM with your address.
BTW- make sure you use red Loctite when you put the throttle shaft back in.

http://www.mcmaster.com/#felt-sheets/=zn8yyc
 

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Discussion Starter #6
Thanks! I went ahead and ordered a sheet I really appreciate your help on this matter. So you're saying use loctite on the nut side of the throttle shaft?
 

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Loctite is for the throttle butterfly screws. If they loosen, they often fall off and get ingested by the engine. Pistons, cylinders and valves seem to disagree with small, hard metal parts. The original throttle plate screws were staked on to prevent loosening.
 

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This is the punch set I used:
http://www.harborfreight.com/6-piece-hollow-punch-set-67030.html

I used a thin piece of modeling plywood with a 5/8 hole in it to hold the felt. I rand the punch on a drill press. It is difficult to get the OD concentric to the ID. I used the 1/2 inch for the OD. On the 450 the shaft measures 222 and the OD is .444 (6 & 12 mm). I think I may have used the 3/16 for the ID. I remember it was a stuff job to get them in. Install the seal on the butterfly shaft end common to the idle screw. Insert the shaft into the carb body. On the end common to the throttle cable, push the seal around the shaft and then stuff it into the carb body. In the first photo is how I found the retainer. The second photo shows the retainer flipped over. I tried to install the seal before the shaft. With the retainer in, the seal just pushed out when I tried to push the shaft through. Since the stock seals are thinner, I would guess 2 mm or .080 inch, the retainer will not fit.

I would be interested to know what sizes you used on the 350. I'm thinking of making some production tools and offering the seals at $5 per carb. I thing the four cylinder Goldwings use the same seal.

I believe I got a tight seal on the throttle shaft. I have read a lot of people who have problems getting the bike to idle correctly. This should be the solution.
 

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Discussion Starter #10
Thanks guys for all of your help. I don't know what I would do without all of the valuable info on this site.
 

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The issue with the Felt seals is they dry out from being soaked in Carb Cleaner.
Usually soaking them in a heavy weight oil will bring back the originals, they just need to swell up a little bit to seal the shaft.
You don't want them to bind up and create a secondary problem by being too thick.
 

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Discussion Starter #12
That makes total sense. I unfortunately learned the hard way about soaking them in carb cleaner. I had a issue with the left carb hanging around in higher rpm's after throttle release and it ended up being the felt washer. I took them out of both carbs and soaked them in oil put them back in fired it up and Voila! problem solved. I can also see your point about being too thick creating a problem, which brings me to the next question. Is the shaft supposed to be completely flush or have slight play?
 

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The issue with the Felt seals is they dry out from being soaked in Carb Cleaner.
Usually soaking them in a heavy weight oil will bring back the originals, they just need to swell up a little bit to seal the shaft.
You don't want them to bind up and create a secondary problem by being too thick.
I do not have a problem with the thickness on my seals. As long as they fit inside the carburator housing you are OK. The side to side movement of the throttle shaft is limited by the butterfly plate in the carb throat.
 

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Has anyone had any luck oiling these felts without disassembly of the throttle shafts? Rather not mess with unstaking and restaking the plate screws and don’t have the patience/time to make new felts
 

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I don’t think that would work well on the CB350T carbs. Rubber O-Rings would probably cause binding and that’s the last thing you want on on the throttle
 
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