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Discussion Starter · #1 ·
Been going through a bunch of stuff due to the bike running weak.

It started here: Wife's 87 TW200 - running weak due to chain and...

Reading back through that post that referred to different final drive gearing and other things, I did not mention that there was some rodent damage to a few wires up by the battery (fixed) and that the intake snorkel under the seat had been chewed.

After putting in a new stock 114 Main Jet as suggested by 'elime' (replacing previous one of same size) there was no difference. However the intake snorkel caught my eye again and made me wonder. Its been chewed on an angle effectively making the opening larger (? to what degree ?) and the downturn is missing entirely (? perhaps draft while riding was affecting it ?).

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(That wire has been rerouted - its to allow battery tender to connect over winter storage).

On a whim I crudely duct taped some cardboard to close off about 1/3 to 1/2 the 'rodent modified' intake opening and low and behold, there was improvement in how it ran!

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Checking the parts houses for the part which fits 87-2000, and it is unobtainium so far.

Anybody have one for sale?

Part number is different for 2000-2022. Is the effective opening size the same?

Anybody have dimensions of the opening of the turned down snorkel end for 87-00?
 

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After putting in a new stock 114 Main Jet as suggested by 'elime' (replacing previous one of same size) there was no difference.
That is disappointing! With your description and my experience and the age of your TW I would have bet money a new jet would solve your problem. If nothing else a worn out jet has been eliminated as a possible cause of your troubles.
 

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Discussion Starter · #6 · (Edited)
Someone needs to start printing these
Bike Bandit, Partzilla, Rocky Mountain ATV - all 'not available' as well.

In addition to what I think is a larger opening than OEM, that downturned snorkel towards the right of the bike may also serve to reduce the effects of wind at speed(?), which could be creating a vacuum that causes my symptoms. It seems the TW might be affected by that per discussions about the foam seal on the bottom of the seat where it mounts near the airbox.

The bike is still not running at 100% but its a lot better. Working on a hit or miss tweaking basis is going to be painstaking. I tried some things yesterday but had heavy winds which added a significant variable into the acceleration and speed maintaining butt dyno results.

I think its a 2 issue approach - 1. blocking off the opening to match OEM size and 2. keep cross wind from coming into play.

I have old ZG1000 carb to airbox boots that might be modified to simulate the downturned snorkel. Those two parallel flanges in the upper 2/3 are similar to the middle of the TW airbox boot - its what made me think of this as a possibility. We'll see.
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TW200 part drawing from fiche: (Number 7)
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I'm not to savvy about what materials can be used for 3D printing.

It would probably need to be rubberized or otherwise flexible enough to get its middle squeezed and mounted properly into the opening of the airbox hole.

Can such material be used for 3D printing?
 

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Honestly I don't think cutting off an inch of the end of the rubber snorkel would make any difference but then I have been wrong before.
This is a picture of an unmolested rubber snorkel. There not much difference between mine and yours. Hard to see what affect it might have.
Now maybe you have a rats nest inside the air box that is blocking air flow, that would make more sense.
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Never had any issues from modifying an airbox. Do not understand how damage to the snorkel would affect performance.

The seat blocking access to the air box or a rat's nest inside the air box are both plausible possibilities.

I increased the intake to the air box on my 2018 XT250. Had zero effect on performance, either negative or positive, if I recall correctly.

Also, the XT250 had factory o-ring chain.
 
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Discussion Starter · #10 ·
I know airbox openings can affect how a bike runs. The DR350 and other dual sport worlds cut specific size holes to enlarge intake to go with increased jetting. It does change how the bike runs.

I do agree with these last posts. I cut modified a ZG1000 airbox boot to slip over the chewed off part of the air duct and provide a downturn like a unmolested OEM one. No Change.

Further testing since the original post, was to then partially blocking the intake to varying degrees. There were changes in how the bike ran, for better and worse. I now think a very strong wind played into that as results wasn't consistent.

Already checked the entire airbox assembly. No rats nests or blockage.

Still pulling my hair out on this thing.
 

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Discussion Starter · #11 · (Edited)
Problem is RESOLVED! I bit the bullet and ordered a Tom Bauer CDI. Today I put it in, still wondering if I’ld get the same unimproved result yet again - which has happened over and over as I went through many different checks of basic things leading up to this.

The bike started instantly and idled higher than it did before the old 87 CDI was swapped out. I thought ‘this is a really good sign!'

Lo and behold, it WAS a good sign! The bike is running much peppier, even better than before this problem arose. Easily got it up to 60+ (for a TW200 anyways) and could still accelerate from there going up an incline. The bike is totally awakened.

Woo hoo, woo hoo, we're jammin' now.

I have been working on this since August when my wife first experienced the issue.

I did every tip and trick I could find on the forum, taking test rides over and over only to realize nothing changed. I can usually get through issues with bikes and was getting frustrated, feeling like I was getting my butt kicked.

This was such a brain buster as there's no real way to test if the CDI is bad other than measuring resistance at a few points, all of which were in spec.

A clue was I got a cheap digital induction tach, and noticed that at around 5500 rpm in 4th and 5th gear was where the weak running was most noticeable. This is right near the timing advance curve the manual shows which is controlled by the CDI.
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Compounding things was early on, a forum member graciously loaned me his known good 87 CDI, which did NOT change the issue when swapped in, leading to the logical assumption that my CDI was not the issue.

The bummer now, is I need to let him know his CDI is probably bad too.

Totally stoked.
 

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If you like playing with your advance curve and timing and electing whether or not you want a rev limiter or at what RPM it works, shift light, etc. then check out Ignitech. Also has spot for electronic tach. Its all adjustable with your lap top.


I bought an Ignitech CDI and played around with it and it works fine. I don't remember what I paid but I thought at the time it was reasonable.

An example of one of the timing curves I experimented with. IIRC blue was stock, red was modified.
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Discussion Starter · #14 ·
Hey Stasch, no worries here! Glad to hear that your '87 is back in business.

I guess the takeaway here is that all '87 CDI's are prone to failure - eventually. So it's great that Tom Bauer has an option that has helped a lot of '87 TW owners!
When I read up a bit before getting the TW, the subject of 'weak electrics' for 87's was one of the things that came up. I got the bike for a great price of $1,100 back in 2015 with 2,100 miles (those were the days) thinking 'what's the worse that could happen?'.

Tom's CDI is about $150 less than OEM and has a 10 year warranty. I swear it makes the bike run better than OEM. It was well worth the money to get the bike running right again with the bonus of knowing the potential 87 CDI weak spot is no more.
 

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Problem is RESOLVED! I bit the bullet and ordered a Tom Bauer CDI. Today I put it in, still wondering if I’ld get the same unimproved result yet again - which has happened over and over as I went through many different checks of basic things leading up to this.

The bike started instantly and idled higher than it did before the old 87 CDI was swapped out. I thought ‘this is a really good sign!'

Lo and behold, it WAS a good sign! The bike is running much peppier, even better than before this problem arose. Easily got it up to 60+ (for a TW200 anyways) and could still accelerate from there going up an incline. The bike is totally awakened.

Woo hoo, woo hoo, we're jammin' now.

I have been working on this since August when my wife first experienced the issue.

I did every tip and trick I could find on the forum, taking test rides over and over only to realize nothing changed. I can usually get through issues with bikes and was getting frustrated, feeling like I was getting my butt kicked.

This was such a brain buster as there's no real way to test if the CDI is bad other than measuring resistance at a few points, all of which were in spec.

A clue was I got a cheap digital induction tach, and noticed that at around 5500 rpm in 4th and 5th gear was where the weak running was most noticeable. This is right near the timing advance curve the manual shows which is controlled by the CDI.
View attachment 232007

Compounding things was early on, a forum member graciously loaned me his known good 87 CDI, which did NOT change the issue when swapped in, leading to the logical assumption that my CDI was not the issue.

The bummer now, is I need to let him know his CDI is probably bad too.

Totally stoked.
Could you share the link to where you got the TB CDI? Be a pal.
 

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Pretty neat one can obtain a aftermarket CDI for the first gen TW! There was a time where Yamaha was only source on a one off system. Often the only definitive way to test early CDI/electronics was replacement with known “good”.
 

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If you like playing with your advance curve and timing and electing whether or not you want a rev limiter or at what RPM it works, shift light, etc. then check out Ignitech. Also has spot for electronic tach. Its all adjustable with your lap top.


I bought an Ignitech CDI and played around with it and it works fine. I don't remember what I paid but I thought at the time it was reasonable.

An example of one of the timing curves I experimented with. IIRC blue was stock, red was modified.
View attachment 232015
I'm interested, can you please tell me exactly which part from Ignitech you purchased? Was it the "SPARKER CDI"?
 

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I'm interested, can you please tell me exactly which part from Ignitech you purchased? Was it the "SPARKER CDI"?
Here is the receipt, the instructions and a picture of it. One end of the cable is serial and the other is USB. It needs a battery with some juice in it for it to work but from what I have heard the battery can be next to dead and it will still fire.
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