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Hello,

I just learned how to ride a motorcycle last June and bought a 1987 TW200 shortly thereafter. I got it for $750, and it did need some work. I noticed from the very beginning that at high rpms, the engine would sputter or act like it was not getting gas fast enough. Since I bought it, I have done quite a bit of work on it including, new tires, new spokes for back wheel, new brakes, valve adjustment, new handle bars, adjusted float valve in carburetor, Used Sea Foam in gas tank several times, new drive chain, and added a DG V2 exhaust. It now runs much better, but it still has problems when I get to about 55 mph. It will do 50 mph no problem, but at WOT, when it gets near 55 mph, it starts sputtering. When I slow down just a little, it does fine. It also seems to have this issue at slightly lower speeds on long rides when the engine is hot. Do you think it is a jetting issue? I believe the bike originated in Washington. I am in New Mexico at about 4,600 feet AMSL. If so, I know nothing about carburetors or how to change the jetting, so any advice would be appreciated. Thanks!

Talon
 

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Welcome!

It could be a jetting issue, especially since you installed a more free-flowing exhaust.

It could also be your CDI going bad. Commonly, when the CDI starts wearing out, it will run pretty well cold, then start sputtering or cutting out when it warms up.

Based on your description though, I'd monkey with the jetting a bit more. Someone will chime in with more specific recommendations, I'm sure.
 

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Welcome to the forum!! :D
 

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If you back off at wide open throttle and it gains speed, it is too lean.

1. What number is the main jet?

2. How high does the needle lift at WOT? (does 1987 have CV carb with a diaphragm operated slide/needle?)

3. How does the spark plug look?
 
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Stock pilot jet is #40. Stock high speed jet is #114. Jets wear out and need to be replaced. They can look perfect even using a magnifying glass but they are not. If you only want to get 2 jets from the dealer get the #40 and #114. Probably cost about $15.

Or go to AliExpress and buy an assortment of each. They don't have a #114 but they do have a #112 and #115. Get 3 of each. And 2 #110 and 2 #118. And maybe 2 #108 and whatever else. Ditto with the pilot jets. A 3 stock size #40 and then a few leaner and richer. Total cost will be about $20 and you will have a lifetime supply or you can share them with friends. And if it still runs poorly then it probably will be the CDI. Send it to Tom Bauer and for $60 he can fix it, or spend $250 on a new CDI which you might have to do anyway.

https://www.aliexpress.com/item/12-main-jet-9-99-and-free-shipping-Off-road-motorcycle-carburetor-engine-TK-JOG/32261782626.html?spm=a2g0s.9042311.0.0.IBBwxr

https://www.aliexpress.com/item/12-pilot-jet-10-9-free-shipping-Off-road-motorcycle-YBR-carburetor-vice-injectors-TK/32261696051.html?spm=a2g0s.9042311.0.0.IBBwxr

Good luck.
 

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I had the same issues as you although I have the newer carb. My bikes had DG pipes put on them and the P.O. had trouble tuning the carbs, I am at sea level and needed to go up two sizes on the main jet. Also I used washers as spacers under the spacer on the needle to raise it. This improved my midrange acceleration. If your bike starts easy then stay with the stock pilot jet. I put bigger pilot jets in and now my bikes start with very little choke or no choke. Luvnot’s recent carb tuning thread has some good references mentioned in it for tuning. There is a YouTube video on how to add spacers to the needle on a TW carb.

Here it is.
 

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Discussion Starter #10
If you back off at wide open throttle and it gains speed, it is too lean.

1. What number is the main jet?

2. How high does the needle lift at WOT? (does 1987 have CV carb with a diaphragm operated slide/needle?)

3. How does the spark plug look?
It does not gain speed when I back off wide open throttle. It slows slightly and stops cutting out or sputtering. The tip of the spark plug is a dull dark brown color. I do not know if you can see it really well in the attached picture or not. It may be running slightly lean. It was running rich before, and I lowered the float a little in the carburetor. It did not like it when I installed a high air flow K&N air filter. I cannot answer the first two questions. I assume the the main jet is stock, but I am not sure. If you could point me to a reference to help me answer those questions, I would appreciate it. Thanks for your help.
 

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It could also be your CDI going bad. Commonly, when the CDI starts wearing out, it will run pretty well cold, then start sputtering or cutting out when it warms up.
Unfortunately I have to second CJPilot with the CDI going bad because it happened to me last year, I also had the same symptoms with my bike until I replaced it with a new one, due to the fact that it is a 1987 makes it a lot more likely to be the cause of the problem (mine is a 1990)

The reason why I say unfortunately is because a new CDI will set you back around US $300
 

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Unfortunately I have to second CJPilot with the CDI going bad because it happened to me last year, I also had the same symptoms with my bike until I replaced it with a new one, due to the fact that it is a 1987 makes it a lot more likely to be the cause of the problem (mine is a 1990)

The reason why I say unfortunately is because a new CDI will set you back around US $300
Being an 87 I tend to agree with you but... the difficult thing with these '87's are the CDI and Carb can have almost the exact same symptom(s). This problem is relegated to just 87 model years of course.

I have a 1983 XT200 with a non stock exhaust which had the same symptoms as the OP states here, stumble at high throttle. It was mentioned to me when I bought it the CDI had been replaced at least twice. Through some trial and error, I discovered mine was a carburetor problem running very rich and it was not the CDI. Just goes to show us it can be anything and hard to rule in or out.

I only mention any of this because the OP has stated the stock exhaust was swapped out for a aftermarket exhaust.
 

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Discussion Starter #14
Unfortunately I have to second CJPilot with the CDI going bad because it happened to me last year, I also had the same symptoms with my bike until I replaced it with a new one, due to the fact that it is a 1987 makes it a lot more likely to be the cause of the problem (mine is a 1990)

The reason why I say unfortunately is because a new CDI will set you back around US $300
Yeah, I know it is a common problem for the 87 models. Right now, for all practical purposes, it runs great. I mostly ride it to work and back in a small town with a top speed limit of 45 mph, and on dirt roads in the nearby mountains and hills. I hope it is not the CDI, but we will see...
 

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Suggest a new spark plug and return the float to stock height, before doing anything else.
The answers to fuel mixture are jets, needle and mixture screw.
Mixture screw is the first to check/adjust. 2 1/2 turns out from a gentle seat is common for sea level to ~5,000 elevation.
 
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Discussion Starter #18
Suggest a new spark plug and return the float to stock height, before doing anything else.
The answers to fuel mixture are jets, needle and mixture screw.
Mixture screw is the first to check/adjust. 2 1/2 turns out from a gentle seat is common for sea level to ~5,000 elevation.
I did install a new spark plug, and I returned the float to the recommended stock height. It was a little high. I will check the mixture screw. Thanks!

Talon
 

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Discussion Starter #19
So, I cleaned the carburetor, replaced the needle valve and all gaskets and installed a 118 main jet. It runs great at WOT! It goes much faster; I had it at 65 mph yesterday with no problems. Before, I could not get it above 55. Now I need to work on the mid-range and idle. It is much harder to start cold, takes a long time to warm up and will surge shortly after takeoff on the first ride of the day. I think I am going to shim the needle and install a slightly larger pilot jet. What size of washers do you use for the shim?

Thank you for all of you advice!!
 

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.020 inch. one should do the job, although at your altitude I should not think you would need any. I'm at 5,700 and it runs fine with the stock 126 and no washers. Did you set the idle needle at 2.0 - 2.5 turns out? That much should be the same even though we have different carburetors.
 
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