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Discussion Starter #1
After cleaning previously on carb I lost the rubber plug that goes inside the carb and it covers something right by the main jet and the pilot jet. So the question is does that plug play a role and cause problems if not there? Also, can you buy an o ring from a parts store for the pilot set screw, it is almost cracked into. I assume that may be why I am having starting problems.
 

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... So the question is does that plug play a role and cause problems if not there?...
Hope you don't mind if I'm not Qwerty.




That rubber plug covers a fuel pick up tube for the choke. There is another fuel pick up tube for the choke right next to it.



I don't know why one is covered by a rubber plug. And I would be more than curious to know if the carb would still work properly without the plug.



BTW, the plug is about $5.00 plus shipping, depending where you purchase it. I'm thinking a creative mind could find a way to plug that hole without spending $5.









Also, can you buy an o ring from a parts store for the pilot set screw, it is almost cracked into
I have looked at Lowe's, Home Depot, and Ace Hardware for an o-ring that small without any luck. Maybe a specialty parts supplier may have one.



Maybe McMaster-Carr or Small Parts.



http://www.mcmaster.com

http://www.smallparts.com/



jb
 

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Use a hole punch of the correct size to cut a plug from a piece of neoprene if you have some.

Brass tubing at hobby shops is available in many sizes. Cut a short piece and chuck it into a lathe or drill press chuck.

As it spins, file it to a cutting edge. It will be good enough to cut a couple of plugs to try out.

If you want a more permanent tool , use steel.



Phelonius
 

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I have some neoprene and also a punch set... give me an O.D. and punch one out and drop it in the mail. Gerry



PS.. I have made a punch on the 'qt' from a socket. I place an extention on the socket. This allows me to carefully turn the OD lip against a fine grinding wheel. I am able to put a nice edge on the lip of the socket. For me, this has never weakened the socket for it's intended use, yet is certainly robust enough to punch thru tuff material. On many sockets, the facets seem to have a slight taper and recess and for me, are not reproduce in the stamping.
 

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The rubber plug is a hair over 7mm in diameter (6mm on tapered end), 4mm thick, and slightly tapered.







The hole it goes into is exactly 7mm. It's a very tight fit.







The only way I was able to remove the plug was by blowing compressed air into one of the carb holes (I don't remember which one). And if you aren't paying attention, that rubber plug will go flying, never to be seen again.



jb
 

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Discussion Starter #7
JBFLA,



Thank you for the info. I think I might have found the plug. Does it look like a T with the top just a little bit wider than the rest of the plug. What I have is solid rubber about 1/4" long and a little flange around the top to make it seal up inside the hole I suppose. I put it in there and it will fit if I press the edges down inside. If we have a side view of it I would know. I will try to get a picture on here to make sure.
 

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Discussion Starter #8
JBFLA,

You were posting as I was typing. What I have doesn't look like that and from what I can tell it will touch the fuel pickup for the choke. Will that be OK or will it be blocking air somehow?
 

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JBFLA, ... it will touch the fuel pickup for the choke. Will that be OK or will it be blocking air somehow?
From what I can tell, without sawing the carb body in half, the 2 choke fuel pickups join together. The one under the plug appears to be completely blocked off by the plug and doesn't do anything.



I'm not sure why Yamaha plugged up the hole. Maybe that was easier than redesigning the carb.



The only way to know for sure is to try the carb on the bike, with and without the plug. I would try it myself but my TW is in NC for the winter, and I'm in FL.



I did remove the carb and bring it with me, to give it a thorough cleaning.



Edit: the 2 choke fuel pickup tubes do join together. I was able to shine a light down one tube, and see the light through the other one.



jb
 

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Quicksand,



I ordered a bag of o-rings for the pilot screw from McMaster-Carr. I think I will have a few extras. They come in a bag of 100.




Hopefully I ordered the correct size. If you don't mind waiting until I receive them, I'll send a couple your way. Just PM me your mailing address.



jb
 

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The reason for the plug is it is very difficult to drill a curved hole. Any material that is gasoline and ehtanol resistant will do to replace the plug. Even a piece of aluminum with an o-ring or two around it will do the trick as long as it doesn't fall out.



Chemical resistance (4 is good, 1 is bad, 0 is unknown)



(Gasoline)ethanol

Aflas (3)0

Buna-N (Nitrile) (4)4

Butyl (1)4

Chemraz (4)4

Epichlorohydrin (4)4

Ethylene-Propylene (1)4

Fluorocarbon (4)4

Fluorosilicone (4)4

Hypalon (1)4

Kalrez (4)4

Natural Rubber (1)4

Neoprene (1)4

Nitrile, Hydrogenated (0)4

Polyacrylate (1)1

Polysulfide (4)4

Polyurethane, Cast (4)0

Polyurethane, Millable (0)1

Silicone (1)3

Styrene Butadiene (1)4

Teflon, Virgin (4)4

Vamac (1)0



Clearly, neoprene is a bad choice for sealing gasoline. Buna-N (Nitrile) is what I use for fuel system o-rings. I get them from Wesley Seals & Supply at 236 W Bedford Euless Rd Ste 4, Hurst, TX 76053, 817-284-3283.
 

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The reason for the plug is it is very difficult to drill a curved hole.
Usually when a curved hole is called for, the cross drilled hole made for the second angle is sealed up with a brass ball. There are 5 of them on the TK carb.







Qwerty, I'm not disagreeing, because I surely don't know the correct answer.



With the tube cast into the carb body, and placing a brass pipe inside it, it looks like too much effort for just a secondary hole, which could have been more easily and permanently plugged with a brass ball.



I'm thinking only a Yamaha engineer will know the exact purpose of the hole and plug.



jb
 

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Discussion Starter #13
Well I put the carb back together and used a temporary o ring for the pilot set screw cut from a larger od o ring with the same id as the oem. Anyway I found the rubber plug I lost and put it back in. I now remember when I took it out originally I chipped the corner of it and it wouldn't fit so good back in there. I shoved it down in there and it feels like it is pretty jammed in there. Anyway, before without the rubber plug I could never use the choke. Tonight for the 1st time I pulled the choke and bamm it revved up and kept it running with the choke on. It definitely would not do that before. I don't know what happened, but I only cleaned out the pilot jet more and cleaned out the Pilot Screw Hole. So I guess that plug helps regulate the choke???????????????
 

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... without the rubber plug I could never use the choke. Tonight for the 1st time I pulled the choke and bamm it revved up and kept it running with the choke on. It definitely would not do that before. I don't know what happened, but I only cleaned out the pilot jet more and cleaned out the Pilot Screw Hole. So I guess that plug helps regulate the choke??????????????
Thanks for the info. It's good to know the plug has a purpose, and it's loss will affect the way the bike runs.



jb
 

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The rubber plug is a hair over 7mm in diameter (6mm on tapered end), 4mm thick, and slightly tapered.







The hole it goes into is exactly 7mm. It's a very tight fit.







The only way I was able to remove the plug was by blowing compressed air into one of the carb holes (I don't remember which one). And if you aren't paying attention, that rubber plug will go flying, never to be seen again.



jb
You'll see it again.... shortly after you've installed the new one
 
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