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Discussion Starter #1
Hey guys,

I want to remove that screw to replace with an inoxidable steel one (I am slowly replacing all the screws on the bike, already replaced the whole engine, front fork, front commands, under seat and tail end of the bike)
I would like to know the size of this screw
Accounting that my bike is a 1993 with a Keihin carby
I assume is this screw right? is already stripped as you can see
WP_20170912_17_37_37_Pro_1505230695519.jpg
 

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Discussion Starter #3
That's more than just a screw and very hard to get out when its buggered. Yamaha PN 14T-14104-00-00

1993 TRAILWAY - TW200E Yamaha Motorcycle CARBURETOR NON CALIFORNIA MODEL Diagram and Parts
Oh, so its not just a regular M4 screw?
Also I notice it is called Air screw, I mean I tought that screw was supposed only to be "opened" and let all the fuel out from the bowl, is correct?
In case it does something more, would be effective to "play" with that screw to improve the TW carburation?
 

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Fuel will come out if you open it, it lets fuel out the hose on the bottom of the bowl. Here's a pic of it:



It won't help to adjust the carb.
 

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Simple screw extractor will get damaged air screw out. images-2.jpeg
Screw can be replaced but really needs a JIS , not Phillips, screwdriver to prevent new damage.
Or one can cleanup up the old screws head ’s a grinder then cut a blade screwdriver bit comparable slot across face of the head. I use a dremel cut off wheel and do a pair of cuts so several blade, #2 phillips, to JIS drivers work. Seat with very little torque!
 

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........

Accounting that my bike is a 1993 with a Keihin carby.........

View attachment 136737
Did you install the Keihin carb?

Just curious as to why it's not a Teikei carb.

On the TK carbs, the screw for the bowl drain serves two purposes.

It enables you to open and close the drain to the bowl, and the tapered part allows the overflow tube to drain even when the screw is closed.

jb
 

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Jannaruto, you are from Spain? I think I remember this, but not sure. I'm not a good mechanic, but do wish you the best of luck with this issue. You have the best advice from this forum.
 

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Discussion Starter #11
Jannaruto, you are from Spain? I think I remember this, but not sure. I'm not a good mechanic, but do wish you the best of luck with this issue. You have the best advice from this forum.
I am Italian, and actually I have no problem with that screw haha, I was just wondering why mine had no spring inside, that's all
I changed with a new one and put the spring that come with the new screw ^_^
 

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Discussion Starter #13
Guys are you all super sure that the float bowl screw (mine had no spring, I replaced with a brand new one with spring) absolutey DO NOT affect any performance right?
 

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No performance gains at all.
Guys are you all super sure that the float bowl screw (mine had no spring, I replaced with a brand new one with spring) absolutey DO NOT affect any performance right?
 

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Proper screw properly installed will not be detrimental to engine performance. It just needs to perform three tasks:
1) Manually drain float bowl when desired.
2) Automatically drain excess fuel from float bowl via the over-flow feature.
3) Not leak
 

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Discussion Starter #16
Proper screw properly installed will not be detrimental to engine performance. It just needs to perform three tasks:
1) Manually drain float bowl when desired.
2) Automatically drain excess fuel from float bowl via the over-flow feature.
3) Not leak
How it will drain? Its a screw, no holes, how it's supposed to drain the overflow?

Also another question, in the back of the carby there is an Y joint with two tubes attached, one very short and one very long
What's the purpose of those? because the little tube that connect the Y to the carby is actually almost completely cutted (is rigid and very old)
 

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The bit of the “Y” pointing down could be where the petrol comes out if you loosen that screw, or an additional carb breather – the bit pointing up is to allow an extra breather, which may help in deep water for instance

The lower pipe is essential, and should be lower than the engine casing – the upper part is optional, and can be tucked in under the seat, or the tank, or even the headstock

If you want to replace the pipe because it’s gone hard, and old plastic pipe will do, battery breather tube for instance – or you could go for the fancy option, which is silicon (from the air pump in a fish tank) ……..
 

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Discussion Starter #18
The bit of the “Y” pointing down could be where the petrol comes out if you loosen that screw, or an additional carb breather – the bit pointing up is to allow an extra breather, which may help in deep water for instance

The lower pipe is essential, and should be lower than the engine casing – the upper part is optional, and can be tucked in under the seat, or the tank, or even the headstock

If you want to replace the pipe because it’s gone hard, and old plastic pipe will do, battery breather tube for instance – or you could go for the fancy option, which is silicon (from the air pump in a fish tank) ……..
No I removed the battery tube because I use a different battery, no acid
The carby actually does not lose fuel from those tubings, if I unscrew the float screw it will lose fuel from.directly under the screw (little hole under) these two tubings are connected to an Y and this Y is connected to a very small hole into the back of the carby, that's why I am questioning the purpose
The tube you mebtioned so long that "surpass" the engine comes directly from under the carby and yes is very long
Any clue on what those two tubes do?
 
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