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Discussion Starter #1
I'm putting a new Carb on my 2001 TW200 and replacing the Carburator Joint\intake boot since several posts in the forum said it can get brittle.
The $10 one I got off of Ebay doesn't have a place to connect the "Yamaha PIPE, INTAKE MANIFOLD Part # 5LB-13584-00-00". Looking at the diagram it connects to a hose\pipe that doesn't really go anywhere and is just terminated with a plug.
What is this pipe for and is it necessary? Can I just use my new joint and remove this pipe or will it cause problems?

I'm also noticing that my joint is 1/8" longer than the OEM joint and the carb is very hard to get in and out so this will make it worse. Does anyone see this as a problem?

TW200-Boot.jpg
 

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Supposedly the " Yamaha PIPE, INTAKE MANIFOLD Part # 5LB-13584-00-00" acts like a surge tower, sort of like the boost bottles of two-strokes years past, or what you have in your house to stop water hammer. Supposedly absords and lessens some of the positive pressure pulses coming back through intake track from intake valve slamming shut that can cause disruption of the vacuum pressure differentials that meter fuel delivery through jets and other metering orifices. It is a carburetor after all, fuel metering works on pressure differentials.
Whether having this intake manifold pipe is critical for smooth operation remains debatable. I would think that Yamaha would have deleted the expense and complication of this pipe and fitting if possible. After all this is not a Honda where elegant engineering is a corporate reward in it's own right. Profits from our TWs help fund R&D expenditures on Yamaha's other race competitive & cost competitive models.
 

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Discussion Starter #4
Ok. Thanks.
It seemed to run fine with the ebay part but I couldn't really take it through it's paces today due to the messy weather.
I put the OEM part back on. It's not too bad yet.

...John
 

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I bought a TK knockoff carb and new boots for my 89. I just capped the tube nozzle and have added @ 750 miles since with no noticeable problems or issues. YMMV
 

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No definitive proof, but I capped that fitting on my stock manifold with no noticeable change in engine operation or performance.

(The plan was to use the hose as a high air vent for the carb...another project I never completed.)

On the other hand, I can't see Yamaha putting the fitting and capped hose for no reason....I have read that other manufacturers (automotive, not motorcycle) change the length of the intake manifold to cancel out back pulses created by air flow in and out if the combustion chamber.

I can't see that would make a measurable difference in the low hp TW engine.

jb
 
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