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Discussion Starter #1
Carb is a TK 30 or whats stock with Main-122, Pilot-40, Needle has what appears to be the numbers 4095 w/o multi clip positions, but a spring loaded mech. that gives the needle approx1-1.5mm of travel towards the richen up side of things.
History: Sat for 15 years and was so frozen up that the slide wouldn't move with a twist of the throttle upon initial tak to fulledown. Soaked in a mix of clear gas and injector cleaner and with some light heat from a propane torch was finally able to remove the slide. Did the initial clean up myself soaking in that same solution with dental picks, toothbrushes and torch cleaning probes and after an initial pull start down the road it would start with or without choke, cold, on 1-3 kicks. Riding it was lackluster, but attributed that to 200cc compared to my usual 400. Continued riding it around with some injector cleaner in the tank(with gas of coarse) and after 8 or so miles something came loose(in the carb) and the bike came to life and would spin or lift a tire if you're looking to do so and I thought "sweet, all good now". Called my friend to pick it up and took a hundred kicks to get a sputter and eventually it started, but ran so poor all it did was pop its way down the alley without any real acceleration. Enrichment knob didn't change for the better or worse during this time. Buddy goes home without the bike i take it apart again and all jets are still clean, but enrichment circuit appears clogged(?) and take the carb to a vintage motorcycle shop that ultrasonically hot bathed and cleaned the carb again.
Present: Put it in after the professional cleaning and still wouldn't start w/o some starter fluid even in the current 97*F weather, but after it was running it idles smooth, no stumbling and warmed up the enrichment knob doesn't affect anything other than raising the idle a few hundred rpms(doesn't kill it).
Now the real problem here: It starts accelerating smoothly for up to about 1/8 to1/4 throttle then it starts stumbling badly until 3/4 to full when, there's more air I presume, but is still not clean and is pretty obviously rich. Spark Plug is a new NGK D8EA and is black and sooty. I've tried bypassing the resistor cap to no avail and spark is present, but more orange /yellow and not overly blue IMO. Hooked up an induction timing light to see if the light starts getting erratic at rpms and it doesn't change, just speeds up as it should.
Checked for an air leak in the air boot, checked valve lash and nothing of note found.
At the stumble on up to full throttle ,when I've had the air boot off, gas vapor can be seen and felt at the back of the carb and once again the chock knob doesn't affect for the worse or better.
At a loss Ya'll. no direct carb replacements for this bike and am trying to stay vintage and keep the original air box/filter setup. Ideas? YouTube links of the offender
 

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Get a brand new high speed jet.

#122 sounds to rich to me. Did you verify that was the original size? If it is the original correct size get a brand new one and see how it runs. If it isn't the original size then get the original size. You might also get a new pilot jet -- and verify #40 is correct or close to it. One or two sizes larger on the pilot jet is usually OK.
 

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Discussion Starter #3
It is most definitely stock, but have been alittle worried that I enlarged the hole in the main while I was cleaning it and ordering those is the only way to get TK them and was thinking it was cheap insurance that that isn’t the problem. It is most definitely rich without a doubt. While I was poking at it today I found that the pickup coil and source coil numbers are low if it should be the same as a TW200. Wire colors are the same so there’s that.
207268
207269
207270
 

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I just restored my 84 XT200. Similar story...it sat in a shed for 20+ years, carb slide wouldn't move.
I cleaned my carb using the PineSol method and installed a new Keyster carb kit. 122 is the main jet for this bike and mine would run with it, but not great at WOT when it got hot. But it would run somewhat normal. I'm now using a 120 main jet, needle at 3.5 clips and pilot screw at 3 turns out and float height set at 24mm (float height affects low speed)

Are you running the stock air box? Stock exhaust? If not, this will affect jetting.

Are you using the original CDI? If so they are notorious for going bad. If its been sitting for 15+ years then it will more than likely be bad. Symptoms of a bad CDI present themselves as carb issues. I ended up ordering a new aftermarket CDI for mine, after I knew my carb was 100% clean and had the new carb kit installed and it still wouldn't run right.
 

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Discussion Starter #6
I just restored my 84 XT200. Similar story...it sat in a shed for 20+ years, carb slide wouldn't move.
I cleaned my carb using the PineSol method and installed a new Keyster carb kit. 122 is the main jet for this bike and mine would run with it, but not great at WOT when it got hot. But it would run somewhat normal. I'm now using a 120 main jet, needle at 3.5 clips and pilot screw at 3 turns out and float height set at 24mm (float height affects low speed)

Are you running the stock air box? Stock exhaust? If not, this will affect jetting.

Are you using the original CDI? If so they are notorious for going bad. If its been sitting for 15+ years then it will more than likely be bad. Symptoms of a bad CDI present themselves as carb issues. I ended up ordering a new aftermarket CDI for mine, after I knew my carb was 100% clean and had the new carb kit installed and it still wouldn't run right.
Carb and air box are stock. 1500 original miles by a teenage girl in the 80s. I’ve been reading that cdi’s have a way of being a”carb like problem”. I am looking for definitive info on cdi diagnosis before I pull the trigger on the cdi since there are lots of post about the trouble of finding one for a later model TW.
 

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Discussion Starter #7
I just restored my 84 XT200. Similar story...it sat in a shed for 20+ years, carb slide wouldn't move.
I cleaned my carb using the PineSol method and installed a new Keyster carb kit. 122 is the main jet for this bike and mine would run with it, but not great at WOT when it got hot. But it would run somewhat normal. I'm now using a 120 main jet, needle at 3.5 clips and pilot screw at 3 turns out and float height set at 24mm (float height affects low speed)

Are you running the stock air box? Stock exhaust? If not, this will affect jetting.

Are you using the original CDI? If so they are notorious for going bad. If its been sitting for 15+ years then it will more than likely be bad. Symptoms of a bad CDI present themselves as carb issues. I ended up ordering a new aftermarket CDI for mine, after I knew my carb was 100% clean and had the new carb kit installed and it still wouldn't run right.
So you say it still wouldn’t run right after the cdi and a clean carb. What was it doing when you say that?What fixed it? Judging by your avatar we have the same bike for sure and I’m really trying not to stray from stock so have not gotten the China carb facsimile that I’d still have to mod the intake or exhaust boot.
 

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It is most definitely stock, but have been alittle worried that I enlarged the hole in the main while I was cleaning it and ordering those is the only way to get TK them and was thinking it was cheap insurance that that isn’t the problem. It is most definitely rich without a doubt.
I am not saying it is the problem for sure but at least eliminate it as a possibility. If its obviously running very rich address that problem first.

Brass corrodes. You clean it out and the hole in the center will definitely be larger and your bike will run richer. Jets wear out. I went through this on my own TW. I did everything I could think of and finally in desperation I bought a new high speed jet and problem solved. I know a couple of other people this happened to too.

As always, my 2 cents worth.
 

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So you say it still wouldn’t run right after the cdi and a clean carb. What was it doing when you say that?What fixed it? Judging by your avatar we have the same bike for sure and I’m really trying not to stray from stock so have not gotten the China carb facsimile that I’d still have to mod the intake or exhaust boot.
Yes, we have the same bike, just different years, mine is an 84 (Canadian model). Normally its white plastics with red frame, but I painted mine to match the 82 colour scheme (I like that colour better).

Here's the timeline of how mine went down...
I cleaned the carb and installed the Keyster carb kit. The Keyster kit is pretty good. It comes with all new o-rings, fuel needle valve and seat, main jet, pilot jet, pilot screw, needle, float bowl gasket. I recommend the kit. As elime pointed out, many of the brass parts will be corroded by now. After the carb clean and kit it would start fine on choke and idle on choke. When I took it off choke it would starve for fuel. Then I read that the XT's (and the TW's) were cold down low and took a long time to warm up and it was recommended to turn the pilot screw out 1 more full turn. Did that...mine is at 3 turns out. This helped quite a bit with the fuel starvation at idle and low throttle speeds, but was still hesitating down low a bit. At this point I could drive the bike for more testing. It was having a hard time going through the entire rev range smoothly and sometimes when it got hot, it would cut out and not start till it cooled down. This is when I suspected the CDI. So I ordered a new aftermarket CDI. You can order them in the US here: CDI Unit XT200 Yamaha
But I'm in Canada and any mail coming to Canada from the US during this pandemic is taking 6+ weeks. So I ended up ordering the same one from a seller in Belguim for cheaper and he shipped it air express and had it in 5 days!

From what I understand the CDI controls the when the spark fires and the timing advance. I gather the old Yamaha electronics weren't great to begin with and when they go with age, the timing can get stuck and/or be sporadic. Anyway, after installing the new aftermarket CDI, the bike revved faster than it did before and was much cleaner through the entire rev range. Oh, I also changed the ignition coil at the same time as the cdi. I read that was recommended too.

Even after the new CDI and ignition coil I was still getting a bit of hesitation at low throttle speeds when cold, this pretty much went away after it was fully warmed up. I then changed the float level to 24mm = a bit more fuel in float bowl before it shuts the fuel off. This has pretty much taken care of low throttle hesitation, it only does it when engine is very cold and I don't let it warm up.

I am currently using the stock carb, but have a Chinese one on order. Hey for $30, its not going to break the bank if it doesn't work.

Elime has posted some good links before on ordering stuff from AliExpress, like main jets and pilot jets, which are hard to find for our carbs. You can actually get stuff a couple $$ cheaper on AliExpress vs eBay...and its the exact same stuff!!
 

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I guess to sum up what I wrote...if the carb is clean and in working order with the stock jets, and you have the stock air box and filter and stock exhaust...and no leaks in the intake or exhaust and you are still having issues, then I would suspect that its electrical related.

The other obvious things to check is make sure the fuel supply is good and clean. Also make sure the valves are adjusted correctly.
 

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I'd love to help but my XT200 has a SuperTrap aftermarket exhaust. While I have experienced some of the same issues, I can't be helpful enough with what type of jet to use. Lots of good advice has been given. Good Luck.

P.S. ...and yes, my XT200 is a cold-blooded starter as well except for in the heat of the summer. Anything below 50F. and it's a little #itch to start.
 

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Discussion Starter #12
Definitely doing the new jets.
Yes, we have the same bike, just different years, mine is an 84 (Canadian model). Normally its white plastics with red frame, but I painted mine to match the 82 colour scheme (I like that colour better).

Here's the timeline of how mine went down...
I cleaned the carb and installed the Keyster carb kit. The Keyster kit is pretty good. It comes with all new o-rings, fuel needle valve and seat, main jet, pilot jet, pilot screw, needle, float bowl gasket. I recommend the kit. As elime pointed out, many of the brass parts will be corroded by now. After the carb clean and kit it would start fine on choke and idle on choke. When I took it off choke it would starve for fuel. Then I read that the XT's (and the TW's) were cold down low and took a long time to warm up and it was recommended to turn the pilot screw out 1 more full turn. Did that...mine is at 3 turns out. This helped quite a bit with the fuel starvation at idle and low throttle speeds, but was still hesitating down low a bit. At this point I could drive the bike for more testing. It was having a hard time going through the entire rev range smoothly and sometimes when it got hot, it would cut out and not start till it cooled down. This is when I suspected the CDI. So I ordered a new aftermarket CDI. You can order them in the US here: CDI Unit XT200 Yamaha
But I'm in Canada and any mail coming to Canada from the US during this pandemic is taking 6+ weeks. So I ended up ordering the same one from a seller in Belguim for cheaper and he shipped it air express and had it in 5 days!

From what I understand the CDI controls the when the spark fires and the timing advance. I gather the old Yamaha electronics weren't great to begin with and when they go with age, the timing can get stuck and/or be sporadic. Anyway, after installing the new aftermarket CDI, the bike revved faster than it did before and was much cleaner through the entire rev range. Oh, I also changed the ignition coil at the same time as the cdi. I read that was recommended too.

Even after the new CDI and ignition coil I was still getting a bit of hesitation at low throttle speeds when cold, this pretty much went away after it was fully warmed up. I then changed the float level to 24mm = a bit more fuel in float bowl before it shuts the fuel off. This has pretty much taken care of low throttle hesitation, it only does it when engine is very cold and I don't let it warm up.

I am currently using the stock carb, but have a Chinese one on order. Hey for $30, its not going to break the bank if it doesn't work.

Elime has posted some good links before on ordering stuff from AliExpress, like main jets and pilot jets, which are hard to find for our carbs. You can actually get stuff a couple $$ cheaper on AliExpress vs eBay...and its the exact same stuff!!
So this Keyster kit comes with a new adjustable needle? The one that’s on the us spec carb has a little spring and isn’t adjustable other than shimming it up into a permanently rich position. I will go cheapest mod first and get those jets both ordered. I will try new stock sizes first. I’ll start looking at options for the cdi(have a link for the one you got?)Thanks for the replies so far.
 

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New aftermarket CDI off ebay (located in Belgium):

Same aftermarket CDI from a US distributor (more expensive):

I ordered my Keyster carb kit here, located in the US and has a pic of what is included. Great guy to deal with:

207282


So this Keyster kit comes with a new adjustable needle?
Yes, it comes with a new jet needle - has e-clip so you can move the needle up and down to make mid range richer or leaner. Also comes with new pilot jet screw. The pilot jet screw is capped off, but you can carefully drill a small hole in the cap and pry it off to gain access/replace. It also comes with a new main jet, pilot jet too.
 

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Back when I was having carb troubles I bought a carb kit and I think it might have been a Keyster. I installed it and the bike ran worse. I put the OEM parts back in and continued on looking for a solution to my problem.

IMHO, fix what you know is wrong for sure first, then move on if the troubles persists. If it is running rich...........
 

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Back when I was having carb troubles I bought a carb kit and I think it might have been a Keyster. I installed it and the bike ran worse. I put the OEM parts back in and continued on looking for a solution to my problem.

IMHO, fix what you know is wrong for sure first, then move on if the troubles persists. If it is running rich...........
A few years ago folks were buying the Keyster kits and there was nothing but trouble with them. OEM is the better way to go IMHO.
 

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Interesting. If I had known that, I wouldn't have bought my Keyster kit. However, I installed it and its been fine.
 

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Discussion Starter #17
New aftermarket CDI off ebay (located in Belgium):
[/URL][/URL]

Same aftermarket CDI from a US distributor (more expensive):

I ordered my Keyster carb kit here, located in the US and has a pic of what is included. Great guy to deal with:

View attachment 207282


Yes, it comes with a new jet needle - has e-clip so you can move the needle up and down to make mid range richer or leaner. Also comes with new pilot jet screw. The pilot jet screw is capped off, but you can carefully drill a small hole in the cap and pry it off to gain access/replace. It also comes with a new main jet, pilot jet too.
Looks like a no brainer in getting that kit. I’ll try that then the cdi.
Back when I was having carb troubles I bought a carb kit and I think it might have been a Keyster. I installed it and the bike ran worse. I put the OEM parts back in and continued on looking for a solution to my problem.

IMHO, fix what you know is wrong for sure first, then move on if the troubles persists. If it is running rich...........
what was your problem and how eventually did you solve it?
 

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what was your problem and how eventually did you solve it?
My TW was running rich. It had a WOT miss and wouldn't rev past 8800 to 9000 rpm.

A new stock high speed jet (#114) solved all my problems. I later installed a #112 jet and performance was enhanced even further as determined by the butt dyno. Will now easily rev past 9500 rpm.

As an aside, the needle in the rebuild kit I bought was shorter than the stock needle.

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