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Discussion Starter #1
I bought a 1996 TW200. Odometer reads 1650. Battery was dead and replaced. Throttle rusted and froze. I freed the throttle. Compression is 140psi cold. Fuel system is clean and fresh. I did not run it before bringing it home. My bad.

I started it up with the choke full out. It ran very fast and continuously. Push choke in slowly, it slows as expected. Push more in all the way and it starts coughing and backfiring through the intake. Will not run at idle nor can I open throttle before it quits.

I cleaned the carb thoroughly and used a Shindy carb kit. I did not replace the needle because I didn't think it was necessary with so few miles. The results were pretty much the same. So, I replaced the Shindy kit jets with the original jets thinking maybe it was because I didn't change the needle. Drilled out the idle screw plug so that I could adjust it. No change in the way it runs. I also replaced the fuel cut off diaphragm.

I don't believe there is anything wrong with the valve train. To me timing comes to mind. Runs like hell with the choke full out.

So now I am out of trouble shooting ideas. I need some ideas or feedback from you guys. I have never worked on a TW before. Please help.

Thanks, Greg Nolan, Clarkston MI
Elevation: 700 feet
 

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Hi Greg, Sounds like you are doing things as close to right as we can get but what you are experiencing is why I often say it is good to have 2 TWs in close proximity at all times. I fell it is a carb issue and I did not have any luck with after market carb kits. If you had a second TW that was running good you could simply swap carbs and know the answer if the carb is the issue almost immediately. My very first TW had the very same issue you describe and I lost a bit of hair trying to get it running smooth. Out of complete frustration and after yanking and rebuilding the original carb more times than I care to mention I just bought a new OEM carb for about $265. I pulled the plug over the pilot screw and set it at 2.25 turns out and slapped it on the bike. I was both amazed and thrilled that my stumbling TW came to full life with not another burp and I never had to yank the carb again. Later on I rebuilt the old carb after letting it sit in a can of Barrymans carb cleaner for over a week and when I got my second TW with carb issues I put the clean carb on it and it worked great. I am a firm believer there is an orifice inside these carbs that does get clogged and we just can't see it. Probably the one above the float needle valve IMO. I have since rebuilt a number of TW carbs and still had no luck with the aftermarket kits parts but they all come back to life with all OEM Yamaha parts. Diagnosing the issue is the key to getting the bike running right and starting with a good working carb from another bike will show you where the problem is real fast.

GaryL
 

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Discussion Starter #5
Hello Gary
Thank you for the response and with clear details. As stated above, I pulled the carb, cleaned it and then used Shindy kit parts except the Needle. I then put the OEM Main and Pilot jets back in it, to get back to OEM status. There was really no change. So, like you say, I will pull the carb and soak it. Changing/adjusting the idle screw had no positive effect. I was also thinking of getting an aftermarket CDI from TomB to see if that made any diff. Tom's CDI would probably be a nice upgrade anyway. I wish there was a replacement carb I could buy thats pretty much a plug and play install. I am not a fan of the TK carb. But I don't want to bastardize my TW too much either. Thanks again.
Greg
 

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Hello Gary
Thank you for the response and with clear details. As stated above, I pulled the carb, cleaned it and then used Shindy kit parts except the Needle. I then put the OEM Main and Pilot jets back in it, to get back to OEM status. There was really no change. So, like you say, I will pull the carb and soak it. Changing/adjusting the idle screw had no positive effect. I was also thinking of getting an aftermarket CDI from TomB to see if that made any diff. Tom's CDI would probably be a nice upgrade anyway. I wish there was a replacement carb I could buy thats pretty much a plug and play install. I am not a fan of the TK carb. But I don't want to bastardize my TW too much either. Thanks again.
Greg
Here is the carb. https://www.partzilla.com/product/yamaha/2JY-14301-03-00?ref=1619dc4d0f09153d3ea51d85ce043dae27121526. Plug and play for sure but a bit more pricey than the last one I bought. You might find it cheaper elsewhere and any year carb between 1987-2000 will drop right in plug and play.

GaryL
 

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When the choke is full out it runs very fast. My guess, more than 3k rpm.
I call that "Runaway Fast Idle" the warmer the engine gets the higher the RPMs will go. Pull the pilot screw completely out and make sure there is an O ring on it.

GaryL
 

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Discussion Starter #10
Gary,
The jet I call the Main jet is in the center of the Bowl and guides the needle. The Pilot jet is inside the bowl. The Idle jet is external from the bowl and adjustable. I have an O-Ring on the Main Jet and on the Idle Jet. It sounds like you call it the pilot jet and I call it the idle jet. I never saw an O-Ring on what I call the Pilot Jet.
 

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Gary,
The jet I call the Main jet is in the center of the Bowl and guides the needle. The Pilot jet is inside the bowl. The Idle jet is external from the bowl and adjustable. I have an O-Ring on the Main Jet and on the Idle Jet. It sounds like you call it the pilot jet and I call it the idle jet. I never saw an O-Ring on what I call the Pilot Jet.
You are half right Greg. I never said the pilot JET which is inside the float bowl. I did say the Pilot SCREW which is outside and forward of the float bowl and between the cylinder head and usually has a protective plug over it so you can't adjust it until the plug is pulled. Part number 4 in this diagram.
https://www.partzilla.com/catalog/yamaha/motorcycle/2000/trailway-tw200m/carburetor. Part number 39 is the little plug that needs to be pulled out.
 

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Discussion Starter #13
Gary,

Ah. Ok. got it. So you say Pilot Screw and I say Idle screw. Thanks for that. There is an O-ring on the Main Jet and Pilot/Idle screw. I will check the intake manifold and will probably soak the carb again. It's got to be something stupid and/or I'm the stupid one. But it is just the same way as I found it. I was very careful. I did not check the float dimension. Not sure what the spec is and how to measure. I may eventually try a Mikuni VM26-606 Carb and a new CDI module from TomB.

Thanks for your help and to anyone else that can share any experience.

GNolan
 

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Gary,

Ah. Ok. got it. So you say Pilot Screw and I say Idle screw. Thanks for that. There is an O-ring on the Main Jet and Pilot/Idle screw. I will check the intake manifold and will probably soak the carb again. It's got to be something stupid and/or I'm the stupid one. But it is just the same way as I found it. I was very careful. I did not check the float dimension. Not sure what the spec is and how to measure. I may eventually try a Mikuni VM26-606 Carb and a new CDI module from TomB.

Thanks for your help and to anyone else that can share any experience.

GNolan
Greg, I call it the pilot screw because that is the name Yamaha calls it. Best if you study the diagram I sent you here and call the parts the name they use so there is no confusion in the future. If you notice part number 22 is called the Throttle screw set which is how you set the idle once the carb is running correctly and I would call that the idle screw if I didn't know the correct term. The Pilot screw number 4 is actually your adjustment for the air to fuel ratio and you can lean the carb out or richen it up with that adjustment but it must be adjusted after the engine is at full operating temp. Most of us have found that between 2-2 1/2 turns out is about right so we say bottom it in all the way and turn it back out 2 full revolutions and then a 1/4 turn more to start. From that point it might need a slight tweek either way to get your carb purring through all throttle positions and gears. You might feel a slight buck at full throttle or a slight stumble while cranking on it which tells you it needs a tiny turn more or less. The rubber boots on both sides of the carb absolutely must have a perfect air tight seal. Check that while the engine is running at idle and spray some WD 40 or other not real flammable spray around the seals. If the engine revs different when you spray you have a leak. Let me add one additional caution. Some might tell you to do some other upgrades like different jet and shimming the needle. These tweeks can have some beneficial effects in some cases. Never do any such changes until you have the carb working correctly to begin with. Then and only then if you want to try to eek the very last bit of performance from it at least you know the carb was right before you did the changes. I have been perfectly satisfied with the performance once I got the carb tuned right so I don't mess with jet sizes and shims but others here are very happy with those upgrades once they get them dialed in and they are good if you are in very high altitude areas. I hear good reports about TomBs CDI modules but I never try to fix things that are not already known to be faulty. It is always best to go one step at a time and one system at a time when you are fighting with gremlins. If you disconnected the rectangular block on top of the slide there is a very tiny spring that goes inside of that block and in between the two posts that go through it.

GaryL
 

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Discussion Starter #15
"If you disconnected the rectangular block on top of the slide there is a very tiny spring that goes inside of that block and in between the two posts that go through it."

Not sure what you are referring to here. Can you try with other words. I did not remove the slide. I removed the slide housing cover so that I could inspect/clean it. I did not change the needle. I reused the OEM jets after cleaning.
 

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Discussion Starter #16
I am thinking like what Smitty Blackstone posted. Also, yes, I am just trying to get the stock OEM carb right, at this time. I hear you on that one.
 

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"If you disconnected the rectangular block on top of the slide there is a very tiny spring that goes inside of that block and in between the two posts that go through it."

Not sure what you are referring to here. Can you try with other words. I did not remove the slide. I removed the slide housing cover so that I could inspect/clean it. I did not change the needle. I reused the OEM jets after cleaning.
Shown as part #3 in the diagram. It is a connecting link on top of #20 valve, throttle they call it a bracket. If you did not disconnect it then don't bother. My first TW had the carb rebuilt by a dealer shop before I bought it and it did not run good at all. I yanked my hair out trying to get it running right with no success. Bought a brand new carb that worked perfect out of the box. Then I sat at my dining room table and took both the new and old carbs apart piece by piece. The new factory carb had the tiny spring inside the bracket block and the dealer rebuilt carb had the tiny spring on top of the needle set #19 and in the absolute wrong place. The lesson I learned there was just because some jack wagon dealer mechanic rebuilt the carb before I got it does not mean he knew what he was doing. The guy sold me the bike because he could never get it to run right even after spending stupid money for the dealers top mechanic to go through it. I got the spring where it belonged and it purred like a kitten. Trust yourself and no one else and don't ever assume the guy who fingered it before you knew what he was doing. We have a great member here named JBfla who was my personal guru on the old style carbs and he got me straight. He has some great pictures in the technical write up section on the very top of this tech section. There are a few others here who can rebuild these old style carbs with their eyes closed so everything you need to know is at your finger tips in the TW200 forum.

GaryL
 

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Discussion Starter #18
Hello Gary
I took a fresh look at my TW project. I set out to remove the carb again to have the MC Shop clean the carb body. I discovered that I did not have the intake mounting clamp tight (thanks Smitty). Before tightenin, I double checked the mixture screw and set at 2.5 turns. I started up and after a short time was able to push in the choke and have it idle. Rough but did idle. At one point it seemed like something let loose in the carb and it then idled even better. As I went along I was adjusting the throttle stop. The idle seems to be on the high side but if I came down on the idle with the throttle stop, it would want to back fire through the carb. Then I put the air filter back in it and this seemed to help the idle even more. Without experience with this engine I really don't know just what to expect. All in all it was very positive progress.
I did notice a problem. While at idle, I goosed it a couple times. Response was good but I noticed that the engine did not return to idle right away. Almost like a car with an anti decel solenoid on it. Seems to me that it should have just dropped right back to idle quickly. Is it typical for these engines to behave that way? On we go...
 

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Get a parts diagram and take apart your carburetor piece by piece. Verify everything is present and where it’s supposed to be. You may have a misplaced, missing, or damaged part and never know it unless you do. With the parts diagram its pretty simple and straight forward.
Just like GaryL, I purchased a 2002 TW that was in great shape but idled strangely and ran poorly. I dissected the carb and found the little spring on the top of the needle was missing. After I replaced the missing part it now runs great.
 

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Discussion Starter #20
Gastone
Yeah. I see that spring. It looks like it keeps the needle seated. Otherwise the needle would float somewhat and could rise causing the idle delay. Thanks for that good information. Gary stated that but I did not study the parts diagram well enough. It makes sense.
 
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