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Carb Screw identification help

14942 Views 13 Replies 6 Participants Last post by  Russandkava
I have been reading for the last couple of hours, I did use google to search the older forums.



I have a question as quite honestly I am new to carborated motors. I have worked on cars and my last bike I owned that I messed with was before I cared or even knew to be concerned with these things. Previous to this new TW I had a few quads, they were so new it was a non issue.



I have the first TW which is a 2006. I have read time and time again that they are most likely too lean from the factory.



I see a lot of info on the older carbs and am so new at this I don't completely understand the difference. Also a lot of posts are not for newbies like me and don't have pictures!









MY QUESTION:



At Bikebandint they have the exploded view of my 2006 Tw200 carb:



http://www.bikebandit.com/houseofmotorcycles/2006-yamaha-motorcycle-tw200v-tw200/o/m7782







What screw am I turning the suggested 2.5 - 2.75 turns out as a starting point?



Is it screw # 27 "Air Screw Set"





Or is it screw #16 "pilot Screw set"





The reason I am confused is that I have been reading it that the idle or air set screw is under the plug on the bottom of the carb... but according to this parts breakdown the pilot screw is under the plug and on the bottom.



I am not sure if the newer carbs changed the location or if I am just incorrect in my understanding.









I realize I will gently screw it in till it bottoms and count where I began, in case I have to go back, and then turn it 2.5 to 2.75 turns out and see how she runs.



There is no big issue right now, it even starts without the choke on for the most part. However I am afraid that under a load or when me and the wife are both on the bike (<320 lbs) that we may put more stress on the motor if its lean. I would rather lose a bit of mileage and keep the engine colder.





Its greatly appreciated.



Thanks
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What screw am I turning the suggested 2.5 - 2.75 turns out as a starting point?


Bottom view of the TK carb, 2001 and newer TW's:







Different names for the same thing. I usually call it the idle mixture screw. It regulates the flow of fuel through the pilot jet (which is inside the carb).



My stock idle screw setting was 1 3/4 turns. Everyone's setting may be slightly different. I believe Qwerty has posted instructions on how to set the idle screw.



jb
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Did the plug just pull out with the screw or do have to drill it at all?
The plug has a tiny hole in it. I used a thin self tapping screw to screw into that hole, then gently rocked the screw side to side and pulled with the pliers. It came right out.



You can enlarge the small hole with a drill bit if you like. Just don't drill too deep. The plug is ~2mm thick.



jb
Since we are on ID the carb screws, which one is the float chamber drain screw? 0 service manual it says "drain the carb with the drain screw" but there's no reference in any dia I thought it should be #27, but it is labeled as air screw set - that doesn't seem correct...
Hi Wes, the label on the parts diagram is wrong. The one labeled "air screw" is really the float bowl drain screw.







On the TK carb there is no air screw, only a fuel mixture screw.



jb
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So is the adjustment method different then for adjustments, or even a re jet?
I'm not sure if I understand your question. The method for adjusting the idle mixture screw is the same.



If you are going to rejet, or add shims (washers) to the fuel (main jet) needle, that should be done first.



Adjustment of the idle mixture screw should be done last. Any change in jetting or raising the needle will change the setting of the idle screw.



If you make no changes to the stock jets or needle, then adjusting the idle mixture screw is all you do.



From the factory, the stock setting is a bit lean. Usually you only need to open the screw a half turn or so in order for the bike to start easier and run a bit cooler.



Temperature, humidity, and altitude all affect the idle screw setting. That's why each bike may have a slightly different number of turns.



jb
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...carb with no air screw then different for adjustments, or a rejet?
There is no air screw on the older style carb either, as far as I can tell from the parts diagram, only an idle mixture screw which they call the pilot screw.



I believe the confusion is coming from the mislabeling of the float bowl drain screw as the air screw, which has nothing to do with adjusting the idle circuit.



Hope some of this helps.



jb
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