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Discussion Starter #1
ok, so the previous owner of my 1987 tw200 removed the little brass plug on the carb and the fuel/air mixture screw is exposed. so, i have a feeling that he also adjusted it. the bike seems to sometimes hesitate when giving it throttle and have little "hiccups" when cruising/ have little engine power surges(thats the best way i can explain it.haha). ive been through everything i could think of and this is the last thing i can think of to cause this problem. i was wondering if anyone can give me some insight on adjusting the screw for maximum performance as well as the factory reset...? thanks!
 

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hey, i came across this and was wondering if this is the newest(smoothes) tw carb? http://www.cheapcycleparts.com/model_years/6441-yamaha-2009-tw200-tw200y/assemblies/212132 and also if it would be worth switching to in comparison to the old style 1987 model carbs? thanks


IMHO, it's not worth switching, except under extenuating circumstances, like your carb is ruined and you happen to have the newer style carb on hand. Even then, it may be more trouble than it's worth.
 

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Discussion Starter #5
the stupid fuel mixture screw is impossible to get to on this thing unless i take off the throttle cables and twist it horizontal. then i have to put everything back on and test it. and then i have to keep repeating till i get the setting just right!
 

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Discussion Starter #8
now the damn thing is still doing it. sounds like its dropping a cylinder. if it is a misfire issue, is the ignition coil a good place to start?
 

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Discussion Starter #9
ignition coil is fine. i tuned the fuel mixture screw to the point that it runs good at low rpms but as soon as it hits mid-high rpms it surges, and backfires as i let off the throttle. it has a new spark plug and when i took it out the blug base was black but the tip had a little white on it. almost as if it runs lean and fat...wow, is this possible. im starting to think i should rejet. what size jets should i get/what kind of washers to shim the needle? i still have the stock airbox....
 

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I have had a couple 87 and they seem to like 116-118 yamaha jets upto 4k elevation, haven not shimmed them

Pilot at 2.5 and 3 turns is good.

Clean filter and lightly oil it



Make sure it is getting fuel, make darn sure the petcock flows. Screens may be clogged. Use clear fuel line, also the the float could be a problem, the needle and seat could be clogged and or blocked with debris. There is a small fine screen on the top of the needle and seat and it does not take much to clog it. Even if you cleaned the carb you shouldchange the needle and seat as a pair. Make sure your vent tubes are clear and the gas cap is venting (non-CA), there is a small bb check valve that gets stuck closed.
 

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First, do a complete tune and service of the motorcycle BY THE BOOK. Read and follow the instructions. Most of the time, that will cure what ails a bike.



If not, trying to fix a drivability problem before an adequate diagnosis is done is like trying to have sex with no blood flow to the vital organ. You can use the diagnostic procedures in the repair manual. Most of the time, that will find the problem. Yes, diagnostics takes an investment in test equipment and lots of time and patience, but it saves money and time in the long run unless you're really, really lucky.



If problem persists, I suggest careful disassembly, cleaning, and inspection of every carb component. Unless you live at high altitude, or outside North America, go with the same main jet the rest of the world gets, put a small washer under the needle circlip, and open the pilot screw to 2 turns. That will be real close to perfect. Carefully inspect all fuel, vacuum, and vent hoses for cracks, tears, kinks, and expanded ends. Heck, hose is so cheap, just go ahead and replace it all. The reason I start with the carb is because it's a heck of a lot cheaper if nothing is wrong than the CDI, and if it isn't the carb, the bike will run really good once the ignition is fixed.
 

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Discussion Starter #13
i have literaly done most everything except adjust the valves. next step is to rejet. im just confused as to what jets to use since it is the old style 1987 carb. i live at about 210ft above sea level. it has a #114 main in it now(which is stock)
 

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i have literaly done most everything except adjust the valves. next step is to rejet. im just confused as to what jets to use since it is the old style 1987 carb. i live at about 210ft above sea level. it has a #114 main in it now(which is stock)


this was posted awhile back, I think it is what you are looking for.



I have had a couple 87 and they seem to like 116-118 yamaha jets upto 4k elevation, haven not shimmed them

Pilot at 2.5 and 3 turns is good.

Clean filter and lightly oil it
 

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I need to do a writeup on my ride-along timing light setup.



In a nutshell, I have a timing light that I cut the aligator clips off of, then wired to a Batter Tender plug. I hook this to the tender plug on my bike, attach the inductive pickup to the plug wire, put a rubber band around the trigger then go for a ride.



When the thing craps out on me I leave it WOT, let it roll and watch the light. No light, or intermittent light, it's a spark/ CDI/ electrical issue. Steady light, carb issue.



Saves me a bunch of aggravation.



I don't wanna freak you out, but '87's are notorious for having their CDI's fail in the manner you've described. I hope that is not the case with your bike, but if you've done everything else it's worth a look, and this is the quickest way I've found to get it done.



Beats wondering and guessing.
 

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Discussion Starter #16
im pretty sure it is the carb because when i tuned around with the fuel screw i could recreate the problem even worse. i took the carb apart one last time today and fund some dirty grit in the diaphram and the seat for the float needle i was finally able to pull out, had gunk all over the litle mesh filter on the bottom. im not sure how that could cause the symptoms i had(sputtering that got worse throughout the powerband). thanks!
 

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Discussion Starter #17
should i leave the #114 jet in there now that i have to replace the needle and seat or should i put the #116 in there as well as replace the needle and seat? thanks
 

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im pretty sure it is the carb because when i tuned around with the fuel screw i could recreate the problem even worse. i took the carb apart one last time today and fund some dirty grit in the diaphram and the seat for the float needle i was finally able to pull out, had gunk all over the litle mesh filter on the bottom. im not sure how that could cause the symptoms i had(sputtering that got worse throughout the powerband). thanks!


I think this was posted earlier.



Make sure it is getting fuel, make darn sure the petcock flows. Screens may be clogged. Use clear fuel line, also the the float could be a problem, the needle and seat could be clogged and or blocked with debris. There is a small fine screen on the top of the needle and seat and it does not take much to clog it. Even if you cleaned the carb you shouldchange the needle and seat as a pair. Make sure your vent tubes are clear and the gas cap is venting (non-CA), there is a small bb check valve that gets stuck closed.





The sputter may have gotton worse because od fuel starvation
 

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#116, if you have one. Take the needle to a hobby or hardware store and get a flat washer that will barely fit around it. Tiny little sucker. If it has sharp edges from being stamped, that will increase its thickness, so put it on a smooth surface and hit it with a flat hammer face to level it out. With a #118 main, you probably won't need a washer so thick, so sand it a bit on emery paper to thin it out. Or, you could go out and buy a jet kit and spend $30 more to do the same thing.
 
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