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1973 CT3 Carburetor Questions

01 Jun 2020 13:18 01 Jun 2020 13:19 by rjmorgan13.
rjmorgan13
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1973 CT3 Carburetor Questions #1
I hope this is a quick one... I am working on my carburetor and I have a hole at the bottom of the bowl that sits toward the end of the banjo bolt. Gas leaks out of this hole. I cannot find a picture to reference whether something need to be there to keep it from leaking. I looked at the parts diagram and all I could see was perhaps a vent hose.

Any help would be appreciated.

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01 Jun 2020 13:57
Swoop56
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1973 CT3 Carburetor Questions #2
That vent is an overflow tube from the float bowl .
Either your float height has been set incorrectly , or float needle / seat isn't shutting off properly .
The float arms should be parallel to the bowl gasket face , with the adjusting tang just resting
on the float valve . If that setting is correct , check for some debris under the float needle which
could be preventing valve closing completely . Otherwise a replacement may be in order .

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01 Jun 2020 14:14
rjmorgan13
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1973 CT3 Carburetor Questions #3
Thanks for the quick reply.. Perhaps I do not understand how the fuel does not simply leak out of this hole all the time. The hole through the banjo bolt ends right at that overflow hole.


Is there some kind of vudoo that I may know know about?


I will try to get all the setting correct to see if that will remedy this issue.

Thanks

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01 Jun 2020 14:56
RT325
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1973 CT3 Carburetor Questions #4
Have a look at these pics i googled & can see how the bowl breather pipe sits above the theoretical fuel height. There's a short copper tube that gone walking that the breather/overflow hose fits to. In saying that, unless there's something unusual going on, the fuel still should not escape out there if the float needle is sealing off or the float level is within spec, but would need to be quite higher than std to spill over down the pipe.Looking in the hole where the pipe fits is there something going on in there. Does that hole link up with the tall tube in the bowl. No way should it link to the main jet housing.


www.hoopriderparts.com/product/1973-yamaha-ct3-175-carburetor

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01 Jun 2020 15:01 01 Jun 2020 15:03 by Mothersbaugh.
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1973 CT3 Carburetor Questions #5
Looks like you are missing a piece of pipe before the attachment of the vent tube to which Swoop56 refers. Look at #37 here:
www.partzilla.com/catalog/yamaha/motorcycle/1973/ct3/carburetor
There is a short piece of (probably) brass tubing which attaches there. Inside the float bowl you will find the stand pipe which is the innards of the vent to which Swoop56 refers. Then #37 attaches to that.

Curses; foiled again! I'm too slow. But now that's two of us in agreement...

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01 Jun 2020 15:11
rjmorgan13
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1973 CT3 Carburetor Questions #6
That is where I am confused. I have a few pictures below showing where all the holes are connected.
The fist pic is through the banjo bolt hole shining directly into the bowl breather.


This one is shining down through the mail jet hole.


And this one is showing where the holes connect.



They are all connected so the fuel seems to me to flow freely out the port hole.

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01 Jun 2020 17:25
Swoop56
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1973 CT3 Carburetor Questions #7
There have been instances of the brass breather tube within the float bowl splitting .
That would cause a leak , even if the fuel level was correct . It's worth a close inspection .

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01 Jun 2020 17:38
MarkT
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1973 CT3 Carburetor Questions #8
You are 100% correct. That hole should be plugged... with a peened in brass ball I think...

Vent hose fitting is on the back side of the float bowl, not the front.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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02 Jun 2020 02:30
RT325
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1973 CT3 Carburetor Questions #9
Well there ya go. I can hear Mr Know-it-all from MX Action Mag saying to me--RT325 you really should have known, & he'd be right lol. So it's drilled in there across to feed the main jet to the jet setter in the middle & then plugged. That'd be a first for one of those escaping. i thought the side main jet was inline with jet setter or maybe on some bigger ones but not on those offset smaller bikes. I think!!.
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02 Jun 2020 06:19
rjmorgan13
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1973 CT3 Carburetor Questions #10
Thank you... I could not wrap my head around this being correct. It makes sense why this would need to be drilled out to create the line for the fuel. I guess it is now time to look for a brass ball to put in there, sound like this is not something that happens much. I was thinking some JB Weld, however the holes and tolerances are so small I would not want to get that in any places that it should not be. I appreciate all your input.

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