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Hey everyone!



I am recently registered to this site, but I have been lurking on these forums for a while trying to figure out why this bike is running so rough.

A 1989 TW200 with 1100 original miles for 200 dollars came across my path last week and I couldn’t pass it up, I absolutely love it except for the fact that it refuses to run right. Overall it is in great condition, the bike is complete, a little rust in the tank from sitting garaged for 18 years of its life.



The PO had very limited mechanical aptitude and explained to me that it could be ridden around for about 20 minutes before it would stall out and refuse to run again. Immediately I thought this was a simple carburetor/fuel level or flow problem and gladly took it off their hands. The bike started right up and idled in their garage before I took it home.

Got it home, checked the valves, drained and added fresh fuel, and did some other routine maintenance things (lubrication points, adjusted levers, chain ect). This bike fired right up and ran like a dream for about 10-20 minutes, then the symptoms started to happen.



The Symptoms:


Rough idle (hesitation, idle increases and decreases randomly)

Dies sometimes when throttle is applied sometimes it backfires and pops without increasing rpms

Backfires

Serious lack of power (that’s if I can get it to move usually it just sits and pops and sputters)

After a cool down period of 10+ minutes (not every time though) it will run/idle/drive perfectly for periods of 4-10 minutes before relapsing

Note: there is fuel in the carb when this is happening, and I have cleaned it thoroughly once and drained it multiple times



Things I have done thus far:


Checked the valves twice for good measure (right within spec)

Checked for obstructions in fuel delivery from the tank to the carb (plenty of freeflow gas)

Checked the float height (does not leak gas or overflow)

Cleaned the carb (took the jets out and soaked them, verified that the orifices were open in the rest of the carb body, cleaned the needle and inspected for damage)

Took apart every electrical connection I could find, inspecting for contamination (everything checked out)

Changed the oil

Tried running it without the gas cap on (no effect)

Tried running it on reserve (no effect)

checked for cracks on the intake boot

The bike has a healthy spark (though I am still going to replace the plug I just haven't gotten around to it yet)



So when the bike runs, it runs great. It will cruise around then it goes through these periods of running like absolute garbage. It seems as though when I leave the bike to cool down when its acting up, but sometimes I just keep running it while its running like garbage and it will run fine for about 20 seconds and then return to running rough. I have noticed that when it is running well it is lacking a bit of power, but the valves are in spec and the high speed jet is not plugged. I have ridden another TW a while back and remember it being more responsive to throttle. What I mean by running fine when the bike is not acting up is that it idles perfectly (no hesitation, rough idle or changing idle speeds) and has throttle response with no backfiring, hesitation or sputtering even when being revved out.



I have looked at almost every carb/troubleshooting/valve adjustment/diagnostic discussion on here and still have had no luck. The carb is very clean, and I don't think that it is the problem based on the fact that it runs so well when it is running.



I am leaning towards an electrical problem, possibly the CDI? When I was lurking I was reading about a few other cases of guys having similar issues (which they thought it was the carb) and ended up replacing the CDI. Unfortunately none of my other buds have TWs so I cant just borrow theirs to see if that's the problem.



Any information and suggestions are welcome; I am thoroughly stumped by this bike.



-Scott
 

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It certainly looks like you have covered the usual suspects



Just to go over I assume Somewhere it got a new spark plug



Does seem heat related as it comes up after its warmed up.

Did you look at the jet sizes, even though it sounds as running lean



Another heat possibility is a weak coil or spark plug boot/cap and wire.



If the carb bowl floats have been slightly bent they can rub against the bowl

sides and lean her out then free itself and back happy



But first always



SEAFOAM IT no I am not kidding
 

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Discussion Starter #3
It certainly looks like you have covered the usual suspects



Just to go over I assume Somewhere it got a new spark plug



Does seem heat related as it comes up after its warmed up.

Did you look at the jet sizes, even though it sounds as running lean



Another heat possibility is a weak coil or spark plug boot/cap and wire.



If the carb bowl floats have been slightly bent they can rub against the bowl

sides and lean her out then free itself and back happy



But first always



SEAFOAM IT no I am not kidding




I'll go out and buy a new spark plug and some seafoam later this week. Ill inspect the spark plug wires/coil as well after I install the new plug. The jets are stock sizes according to the manual. Ill also check to make sure the float in the bowl is functioning properly.



Thanks for your quick response!
 

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So I finally got around to replacing the spark plug and added some sea foam. No change unfortunately. Though I did go through all the electrical connections again and magically it worked until I bumped the CDI off the seat and the bike went back to running rough. Took the CDI inside, let it warm up. Hooked it back up and ran perfectly until I started tapping it against the frame very gently. I ordered a new CDI last night (250 bucks) so hopefully that fixes the problem. Ill keep this updated.



Thanks for your help!



-Scott
 

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Where were you able to locate a CDI for an 89? Has Yamaha taken them off backorder finally? What part # did you use?



Sorry for all the questions but I went through this a while back and had a heck of a time. Just about every Yamaha dealer in the country found them out of stock/backordered with no clue when or if they would have more.



You might want to call and confirm that they actually have the CDI, if it was not listed as "in stock" or something when you ordered
 

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I ordered a new CDI last night (250 bucks) so hopefully that fixes the problem. Ill keep this updated.



Thanks for your help!



-Scott


my 87 did the same thing, new cdi cured mine. i also made sure to put the newer resistor type spark plug in, manual calls for D8EA but id go with the DR8EA. my guess it will help shield the cdi from the high frequency bursts the older one give off
 

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my 87 did the same thing, new cdi cured mine. i also made sure to put the newer resistor type spark plug in, manual calls for D8EA but id go with the DR8EA. my guess it will help shield the cdi from the high frequency bursts the older one give off




I'm experiencing similar symptoms on my 87 but I'm hoping it's a kill switch or kickstand safety issue since I've read that CDI's for the 87 are unobtanium.
 

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Where were you able to locate a CDI for an 89? Has Yamaha taken them off backorder finally? What part # did you use?



Sorry for all the questions but I went through this a while back and had a heck of a time. Just about every Yamaha dealer in the country found them out of stock/backordered with no clue when or if they would have more.



You might want to call and confirm that they actually have the CDI, if it was not listed as "in stock" or something when you ordered


I just sent an email to Babbitt's to make sure they actually had a CDI in stock/ordered from Yamaha. Thank you for the heads up! How did you end up getting your hands on one?



The part number I used was 2YG-85540-M0-00 and I found it on http://www.babbittsonline.com/ for 230 bucks. Though it makes me wonder if they actually have one now.



There were a number of websites with parts fiches I looked at, I just picked the cheapest.



-Scott
 

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Apparently the CDI is on its way from Yamaha and I should have it within a week or so.



Hopefully it fixes the problem!



-Scott
 

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I emailed ThumperTalk as well to see if they had the part a few days ago. They just got back to me and said it is on backorder till Dec 8th, so we will see what happens I guess.



-Scott
 
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