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Discussion Starter #1
I recently picked up a 1992 tw200 with 192 miles. I've cleaned the carbs twice and still can't get it to start and stay running. Here are some of the issues. When I was able to start it, it would only start with 4 1/2 turns out on the air mixture screw. Oddly enough, it would not start with the choke pulled. I have a 40 slow jet and 116 main with 4 shims. It has a new battery and turns over easily. I've resurrected a number of these tw200's but this one has me scratching my head. Any recommendations from you master mechanics would be greatly appreciated.

Thanks!
Ken
 

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Stupid questions but I have to ask. Are you sure the cleaned carb is getting clean fuel where it’s required? Tank, lines, jets etc, all getting good clean fuel? 92 with 192 miles has spent a lot of time sitting. Also, getting proper spark? New plug? Verified spark when turning over?
 

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When you say you cleaned the carb you don't say how you cleaned it. If you rebuilt the carb did you remove the float needle valve cup from the body and check the tiny screen under it? You should actually replace the float needle valve assembly any way and check the height of the float to make sure it is set to the correct height. Fuel/gas must be flowing through the entire delivery system from the tank, through the petcock and into the carb. Check the entire system to be sure there are no clogs. When re installing the carb the pilot SCREW should be set at between 2-2.5 turns out from the full in position and it is absolutely imperative there is an air tight seal on both sides of the carb or you are barking at the moon. Jets and shims! Apparently someone has been in this carb to make some changes. Did that someone put the carb back together correctly??? Are you following his lead and doing the same? Did someone use some BS after market kit. I would go directly back to real OEM stock jets, needle and original form with no shims just to get you back to a working carb. After it is know to be working correctly then you can do what ever additional tuning you like and do it one thing at a time so you know what you just did works or not.
I will assume here, A 1992 with 192 miles sure has sat a lot. The tank likely has crud growing inside and the petcock screens are likely clogged. Any old gas that was in the tank has turned to varnish and you will likely find a rust build up inside. Any stale fuel that entered the carb from the tank probably had all sorts of particles in it that would easily clog the internal passageways and cause the issues you are having. Such a carb requires a complete disassembly and a deep cleaning in an ultrasonic machine or a deep soak in a 1 gallon can of Berrymans carb soak for a few days plus a thin wire pushed through all the passageways. During the reassembly you must follow the diagram and assemble it to factory specs with all parts in the right place as designed and do not depend on the way the one before you had it. If you see rust inside the tank it must be cleaned and there are lots of threads "HOW TO" here. I use Metal Rescue available at the big box stores and soak the inside for a few days with it at full strength. A new petcock is a good idea and order new screws with the gasket washers as well. An in line fuel filter is a major plus also.

GaryL
 

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I think GaryL is on to something when he says someone else has been in there.

I once bought a carb kit that had a #116 high speed jet and a lot of shims along with many of other parts. When I installed all the pieces it ran like very poorly and I ended up putting the original used parts back in.

Here are pictures of some of the pieces from that kit:
Pic #4: Original needle on top. Multi grooved one came in kit.
Does your carb have any of the non original parts in it?
P5190022.JPG PICT2571.JPG P5190027.JPG PICT2564.JPG
P5190023.JPG
 

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One jet kit is not the same as the other, despite the sizes on the packet – plus, you don’t know if those shims (or anything else) has been done to compensate for the introduction of aftermarket parts

I agree with the others – take the carb back to stock with OEM parts, clean it like your life depended on it, and re-assemble it properly (which may be different than its present state) – then take it from there

As it stands, you have no base reference point for any of it …..
 

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Look for everything outside of the carb, first, and eliminate those possibilities. Like has been previously mentioned, make sure it's not starved for fuel. Remove the petcock and inspect the filter on the pickup. Also, a bad CDI will cause it to run crappy - This was the case with the '87 I'm working on. With a bad CDI, it can still fire and run, but with my experience, it wouldn't take any throttle. It would die when you put the fuel to it, and it didn't want to idle.
 

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Discussion Starter #8
Thanks to all who have replied. I’ll provide more background on what I’ve done. So the carb came in stock but the idle (air mixture) screw was turned out 4.5 turns. The brass jets had all corroded to the point that they were pitted so I replaced the idle (air mixture) screw, emulsion tube that holds the main jet, main jet, and pilot jet. All were OEM Yamaha parts. I ultrasonically cleaned the carb (with Simple Green mix) and also sprayed carb cleaner through any passages. I put it back together and it started up okay but again but needed the idle (air mixture) screw at 4.5 turns with no choke before it would start. When I would try to lay on the throttle, it would bog instantly. In the past, I usually added shims to account for this. So I added two shims and it would start and throttle improved marginally but would still bog. I added another two and now I have trouble starting and keeping it running. It will start and run for 1 second and then die. This only works 1-2 times before it won’t start at all. I know that it isn’t the petcock because I have a temporary fuel set up (motion pro) hanging bottle with a direct tube to the carb. So I know it’s not a fuel flow issue. What I will do tonight is take all the shims out and see if it will stay running. My understanding is that the shimmed needle shouldn’t have an effect on idle but I’ll remove just in case.

For the CDI, how do I test to know if it is bad?
 

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For the CDI, how do I test to know if it is bad?
I stuck the CDI in the freezer for an hour or so, and then quickly reinstalled it. The bike would run good for a couple minutes until it warmed up. Though this is definitely not a "tell all" of what all could be wrong, it was enough of an indicator for me to believe the CDI was the culprit. My hunch paid off.
 

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Go here. https://www.partzilla.com/catalog/yamaha/motorcycle/2000/trailway-tw200m/carburetor
Part number 17 and part number 32 could be culprits and you don't mention having replaced them. Number 17 has a tiny fine mesh screen above it which is always clogged when ever there is other corrosion inside the carb. The rubber diaphragm on part 32 is also subject to be cracked and the plunger behind it could certainly be stuck. Using the actual part names given by Yamaha in the schematic helps us to know what parts you have replaced.
Another often faulty part on these older bikes is the rubber boot between the air box and carb that tends to harden and shrink. This will not allow for an air tight seal on the intake side and any air leak on either side is NFG! If you have not personally inspected the air box itself then do so. Mice love to build nests up in the air intake right behind the battery and their nest material will clog the air flow. 4.5 turns out on the Pilot screw #4 is absolutely no good and you might check you plug for fouling as it is running far too rich. # 11 is your pilot jet size 40 and number 14 is your main jet size 114. If all else fails then I will suggest buying part # 1 or sending the carb to someone here who is willing to mess with it. If you have a second TW that is running good then swap carbs and see if this corrects the issue which will immediately tell you if it is or is not carb related. CDIs do fail but that is the very last place I would look before you are certain it is not in the carb.
Part #6 here for the carb joint , https://www.partzilla.com/catalog/yamaha/motorcycle/2000/trailway-tw200m/intake. BTW, Any carb from 1987-2000 is what you are dealing with and we call them the Old Style carbs, they changed in 2001 and the new ones will work however you have to buy the joint boots on both sides and change the cable routing. IMO, new style carbs are not much better than old style ones but I leave that up to you. The 1987 models are very common to have faulty CDIs but from 1988 up the CDI issue is much less common.

GaryL
 

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Discussion Starter #11
So I fiddled more with it last night and got it to start and idle (albeit weakly). Things I did included: 1. Removed all shims. 2. Confirmed stock jets are in (40 slow, 114 main). 3. Turn air mix screw out 3 turns. Started without choke and when I pull the choke, it still dies immediately. Also, as soon as I touch the throttle barely, the bike dies.

Things I'm wondering about. If I pull the choke, doesn't that richen the fuel air mix? It seems counterintuitive that I would need to turn the air mix screw out so much to richen at idle but pulling the choke kills the bike. I am going to check for air leaks tonight by spraying starter fluid around the carb boots and see if that causes the idle to change.

GaryL: I did actually replace the needle valve set. As for the diaphragm set, I verified that it was there and that the plunger behind it was able to be depressed. Would that affect idle and initial roll on of the throttle?

I'll keep fiddling this week with it and look into CDI removal and troubleshooting as well. That part #1 is looking better by the day.
 

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So I fiddled more with it last night and got it to start and idle (albeit weakly). Things I did included: 1. Removed all shims. 2. Confirmed stock jets are in (40 slow, 114 main). 3. Turn air mix screw out 3 turns. Started without choke and when I pull the choke, it still dies immediately. Also, as soon as I touch the throttle barely, the bike dies.

Things I'm wondering about. If I pull the choke, doesn't that richen the fuel air mix? It seems counterintuitive that I would need to turn the air mix screw out so much to richen at idle but pulling the choke kills the bike. I am going to check for air leaks tonight by spraying starter fluid around the carb boots and see if that causes the idle to change.

GaryL: I did actually replace the needle valve set. As for the diaphragm set, I verified that it was there and that the plunger behind it was able to be depressed. Would that affect idle and initial roll on of the throttle?

I'll keep fiddling this week with it and look into CDI removal and troubleshooting as well. That part #1 is looking better by the day.
That pilot screw adjustment is a tricky little bugger. Why are you going so far out with it to begin with? We all say set it between 2 full turns out and some go to 2 1/2 full turns out to find the sweet spot. If I turn mine out to 3 full turns the engine will stall and not re start. Set it at 2 turns out and get the bike running if it will. Allow the engine to come to full operating temp and then and ONLY then can you do the final fine tune which should be in between 2 and 2 1/2 turns out. I believe the diaphragm is a deceleration circuit which keeps the carb from backfiring but if the plunger is stuck or the rubber is cracked the bike will run very rough.
I have purchased 3 brand new OEM old style carbs simply because these carb issues drove me nuts. It is a royal PITA pulling the carb off and putting it back on so many times. When the new carb arrives I yank the plug over the pilot screw and set it at 2 full revolutions out from bottom. Once the bike is running and hot I can then set the final fine tune. All three new carbs performed perfect right out of the box. I went so far as to have the old and new carbs side by side as I opened them both to compare and be sure I did not have some part wrong in the old one. Sure enough I had a tiny spring in the wrong place and my float was not set right. Fixed that and the carb worked perfect. Shims and different jets might be fine if you are riding in high altitude or looking for every last drop of power but they must be done in a known working carb that is running the bike fine to begin with.

GaryL
 

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Discussion Starter #14
Purple: I will check that definitely tonight. Do you simply remove the side cover on the left side? I did that last night and all I see is a metal screen. Should there be some sort of paper filter or foam behind the black side cover?
 

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Purple: I will check that definitely tonight. Do you simply remove the side cover on the left side? I did that last night and all I see is a metal screen. Should there be some sort of paper filter or foam behind the black side cover?
Part number 11 here, https://www.partzilla.com/catalog/yamaha/motorcycle/2000/trailway-tw200m/intake. It is an oiled foam air element. All of this is working against you. The entire intake through the carb has everything to do with how well the bike will run. With no filter element in there you are barking at the moon to try to set the air to fuel ratio going into and through the carb. Also be sure to inspect part #7 which is up under the seat behind the battery box. I have seen mice build nests there and even had one member used that area to stuff a hand wipe rag not realizing he was cutting off the air intake flow.

GaryL
 

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Behind that metal screen, as Gary says, is a foam filter, that has to be oiled to work. Too much oil, and it stifles air flow, too little, and it won’t catch the dust particles. Recommendation is to buy a new one, as the existing one is likely toast by now. Soak it in oil (there are a few products out there, but basic 20W oil will do it), wring it out as much as you can, place it back in the frame, and put the wire mesh back over it

I’d recommend researching the principle of how this type of filter works, which will give you a greater understanding of what’s involved. What is second nature to some, but not be to you – start here https://www.mishimoto.com/engineering/2016/11/filtering-right-stuff-dry-vs-oiled-air-filters/ - but don’t stop there. Research it until you’ve got your head around it

Gary’s next suggestion is just a valid – if you lift off the seat, you will see that there is an air vent under there that acts as a “snorkel” for deep water crossings. This air vent beneath the seat leads down to the air filter chamber, which is a favourite nesting place for all sorts of critters – make absolute sure they are clear of any and all obstructions. It may not be obvious at first, but it is there – find it, and clean it out

Again, until you have done this basic stuff, you do not have a starting point for your problem (although I suspect this will cure a lot of it)

If you don’t know something, ask – there’s no such thing as a dumb question on this board ………
 

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In the very first post Ken said this, I've resurrected a number of these tw200's but this one has me scratching my head.

Every engine requires Air, Spark and Fuel for it to run correctly. In searching for these gremlins it is most important that we begin with some of the basics. Make sure we are getting air, make sure we are getting fuel and make sure we are getting spark. Ken's bike does run, just not very well so he is inside the carb. We already know from his statements he is using a fuel supply outside of the tank. We already know the engine gets a spark and will run but yet to be determined if the spark is right. Now for the air induction part of the equation. Air comes from under the seat and behind the battery box and flows through the air box chamber through an oiled foam filter before it gets to the carb intake side. The seals, called Joints or rubber boots must be air tight. The filter element must be present to accomplish the correct air flow volume and the air intake must not be clogged or impeded in any way so this means check it from top to bottom. The carb itself works off a vacuum produced by the piston and valves which suck air and fuel through it. No air or no fuel or no spark and NO GO. It makes no sense at all to be inside the carb before you know what the other systems are doing or even if they are functioning as designed. Once you know for sure it is getting Air, Fuel and Spark with no leaks or impediments along those routes you can then go inside the carb to chase internal gremlins. These bikes don't run well if any of these systems are not working as designed.
There are other possible gremlins which I doubt here but we have also heard of the previous owners doing a valve adjustment and adjusting them 180 degrees out by not having the piston in the right stroke when adjusting valves. There are good tutorials on adjusting the valves here also. With only 192 miles I seriously doubt you have to go any further than checking the basics and I seriously doubt your CDI has any issue. Your bike is 27 years old with 192 miles and that is around 7-8 miles per year for 27 years. Bad gas, dirty carb, dry and hard boots and critters in the air box is my complete assessment from where I sit.

GaryL
 

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Discussion Starter #18
Purple, GaryL: I think Purple may be onto something. I noticed that there was no foam filter which would assume that it is getting air too easily when I open the throttle now. I'll purchase the replacement ASAP and give that a try. That should be my new baseline anyways. While I wait for the new filter, I'll check for mice nests in the filter area to rule that out. Thanks guys!!
 

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Your new air filter should not require much oil to function correctly. Ignore any of the Yamaha videos that instruct you to pour almost a whole liter of their proprietary Yamaha filter oil on the filter, just a few tablespoons is plenty if worked into all the pores then blotted almost dry. One bottle or aerosol can should last years of dedicated maintenance in my experience.
 

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Discussion Starter #20
Well, no luck still. Other things I tried include:
1. Installed new air filter after oiling. No change. Bike still would not start at 2-2.5 turns of the air mix screw.
2. Turned the air mix screw to 3.5 and bike would start, idle weak, and die after 5 seconds. If I tried to add throttle quickly, it would die. If I rolled on the throttle very slowly, it would surge a bit, almost die, and be intermittent in this fashion. In the end, it would always die.
3. Sprayed starter fluid near the carb boots to see if there was any type of air leak. No change.
4. Choked the bike after getting it to idle at 3.5 turns out on the air mix screw and it would immediately die.

What I suspect:
1. Gut is telling me that it may be the CDI based on what I'm reading.
2. Perhaps there is a passage in the carb that I just can't see that is clogged. All jets are clear so I know that isn't it.

Options:
1. Buy new CDI from member TomBauer
2. Buy new Carb from Partzilla
Both are expensive but looking more attractive by the moment. Any recommendations on which to go with first? Should I place the CDI in the freezer, then install to see if it helps?
 
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