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Discussion Starter #1
I've got an 87 with some carb problems that I cannot figure out. I used to ride the bike all the time with no problems until about 2 years ago. It sat in my barn during that 2 years. A couple months ago I pulled it out to get it road worthly again. Couldn't get it to run, so I bought a Keyster carb kit off ebay (May have been my problem from the beginning) I got the kit installed and fired up and rode for a couple miles and ran great. The next time I went to ride it, it ran horrible. I couldnt get it to idle without the choke on, but I could get it to rev up only if you played with the throttle for a couple seconds. I figured the carb was gummed again. Took it apart again and cleaned several times. No luck. Parts I replaced recently hoping would cure the problem-

1.Both boots on both sides of carb-due to shrinking and small cracks

2. diaphragm kit on side of carb

3. gasket on plastic cover over slide

4. 2 different spark plugs

5. o-ring between carb boot and head.





I read some other posts on here about people having problems with the ebay keyster carb kits? I tried my old main jet and needle and it runs slightly better but no where close to where it should. It will kind of run with the choke about half way out. Adjusted pilot screw 2 1/2 turns out. Checked valves and are both good. Carb is %100 clean. I thought about ordering OEM jets and giving that a try but I hate to just guess. Already spent around $200 on guessing. Any suggestions? Thanks a lot
 

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Discussion Starter #2
Update---- I put in my old main jet and needle and it runs a LOT better but still cant get it to idle and rev at lower rpm's. It will stay idling and run better with about 1/2 choke out.
 

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Sounds like not enough fuel at idle. I believe the pilot jet and screw have the most to do with lower rpms and idle.

If it ran good and now it doesn't, I'd really suspect some kind of fuel obstruction. Debris has a way of working loose in equpment that's been sitting.
 

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... It will stay idling and run better with about 1/2 choke out...
If you need the choke to keep it running after the engine is warmed up, there's not enough fuel coming through pilot circuit , or there is a vacuum leak.



Jb
 

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As you probably already know your first mistake was buying a carb kit. I've cleaned out plenty of gummed up carbs that have been sitting for years and never need a carb kit (maybe a float bowl gasket). The carb isn't worn out, just plugged. Carefully take it apart. Does the idle mixture screw have a little washer and o ring on it? Very easy to lose them if you don't carefully remove them and will not idle right without it. I like to spray carb cleaner thru each circuit and see exactly where its supposed to come out (WEAR EYE PROTECTION cuz carb spray in your eye really really hurts!) Next use your rubber tipped compreessed air nozzle and blow air thru it. Then try to go the reverse thru the circuit. It can be tough to get that tiny flake out so back and forth with carb spray and air. You really have to take your time. * also when you do get it running right. Drain the carb on a regular basis and I turn the petcock off and run the the engine till it quits. Then I drain carb. Don't want it gumming up again. I also use seafoam like a lot of other members here do.
 

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...I like to spray carb cleaner thru each circuit and see exactly where its supposed to come out (WEAR EYE PROTECTION cuz carb spray in your eye really really hurts!) Next use your rubber tipped compreessed air nozzle and blow air thru it. Then try to go the reverse thru the circuit. It can be tough to get that tiny flake out so back and forth with carb spray and air. You really have to take your time. * ...
importmech,



Excellent description of the procedure!!!







Jb
 

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Discussion Starter #7
As you probably already know your first mistake was buying a carb kit. I've cleaned out plenty of gummed up carbs that have been sitting for years and never need a carb kit (maybe a float bowl gasket). The carb isn't worn out, just plugged. Carefully take it apart. Does the idle mixture screw have a little washer and o ring on it? Very easy to lose them if you don't carefully remove them and will not idle right without it. I like to spray carb cleaner thru each circuit and see exactly where its supposed to come out (WEAR EYE PROTECTION cuz carb spray in your eye really really hurts!) Next use your rubber tipped compreessed air nozzle and blow air thru it. Then try to go the reverse thru the circuit. It can be tough to get that tiny flake out so back and forth with carb spray and air. You really have to take your time. * also when you do get it running right. Drain the carb on a regular basis and I turn the petcock off and run the the engine till it quits. Then I drain carb. Don't want it gumming up again. I also use seafoam like a lot of other members here do.




I'll give it another try. Since I did have it running very well after the rebuild, I keep leaning toward something still clogged in the carb. I've sprayed carb cleaner through every port. My kit came with a #38 pilot jet. I tried my old #40 jet after cleaning it well, and it didn't make a difference. I'll give it one more good cleaning in both directions and post what I come up with. Thanks a lot.
 

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Carbs can be a bitch to get cleaned out. I just cleaned out my TTR225 carb and while it runs alot better and starts easier, I still think I missed something inside and will have to do it again....
 

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Discussion Starter #9
Well, I took the carb apart for the 700th time. I used 2 cans of carb cleaner and blasted every port in each direction with my air nozzle. Everything seems to flow fine from what I can tell. I put the new main jet in again and it ran like crap. Switched back to the old one and it ran better again but still wont run unless the choke is 1/2 on. Messed with the pilot screw in and out but doesnt make much difference. Any other suggestions? This thing is driving me nuts.



Edit-

I was just looking at the carb diagram and it looks like there may be a lower gasket that goes to the main jet? Its #12 in the following diagram



http://www.ronayers.com/Fiche/TypeID/26/Type/CARBURETOR_(NON-CALIFORNIA_MODEL)/MakeID/4/Make/Yamaha/YearID/28/Year/1987/ModelID/9234/Model/TW_200/GroupID/443465/Group/CARBURETOR_(NON-CALIFORNIA_MODEL)
 

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If you can't find an intake vacuum leak its just got to be the carb fuel or air circuit plugged. You said it was parked in a barn. any rodent chewing damage? Does the main jet have a tube behind it with little holes in it. Its been awhile since I've cleaned mine so don't remember. I'll have to look at carb pic in my service manual. * looking a pic now. shows an oring on main nozzle and pilot screw. Those both still good?
 

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Discussion Starter #11
If you can't find an intake vacuum leak its just got to be the carb fuel or air circuit plugged. You said it was parked in a barn. any rodent chewing damage? Does the main jet have a tube behind it with little holes in it. Its been awhile since I've cleaned mine so don't remember. I'll have to look at carb pic in my service manual. * looking a pic now. shows an oring on main nozzle and pilot screw. Those both still good?




Yes the main jet has the tube with little holes on the side. It has new o-rings on the main jet and pilot screw. If I get it running with the choke 1/2 on, then turn the choke off, it will backfire some when I let off the throttle. It doesnt backfire when the choke is on. No rodent damage anywhere. I cleaned out the airbox and have a new filter.
 

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OK, well it still sounds like not enough fuel / too much air @ idle. I say this becase of the decel pops and having to pull the choke out to keep it running. I know you've cleaned it to infinity and beyond, but I still think somewhere, somehow a piece of crud is messing you up. Why else would it run good, then run bad. Working backwards, is the fuel tank clean? Is the fuel line fom the tank to the carb new? Do you have an inline fuel filter?



I went to the manual. Troubleshooting for idling problems includes:



Improperly returned start plunger



Clogged or loose pilot jet



Improperly adjusted idle speed (throttle stop screw)



Improper throttle freeplay



Cracked carb joint



Improper tightened screw (carb joint)



I don't know, does that new kit replace the plunger? I hope this gives you an idea. Try spraying around the boots and anywhere around the carb with carb cleaner to see if you might have an air leak.
 

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Discussion Starter #13
OK, well it still sounds like not enough fuel / too much air @ idle. I say this becase of the decel pops and having to pull the choke out to keep it running. I know you've cleaned it to infinity and beyond, but I still think somewhere, somehow a piece of crud is messing you up. Why else would it run good, then run bad. Working backwards, is the fuel tank clean? Is the fuel line fom the tank to the carb new? Do you have an inline fuel filter?



I went to the manual. Troubleshooting for idling problems includes:



Improperly returned start plunger



Clogged or loose pilot jet



Improperly adjusted idle speed (throttle stop screw)



Improper throttle freeplay



Cracked carb joint



Improper tightened screw (carb joint)



I don't know, does that new kit replace the plunger? I hope this gives you an idea. Try spraying around the boots and anywhere around the carb with carb cleaner to see if you might have an air leak.




I've got a brand new tank on it, with new fuel line and inline filter. I've soaked the whole carb and boots in carb cleaner and I couldn't get it to do anything. The kit didn't come with the plunger but I did take it apart today while cleaning. I was wondering if maybe the head gasket is leaking and sucking air? It does run very well though at higher rpms.
 

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Not sure on the head gasket. The manual did say the valves could be out of adjustment, but again, I don‘t know about that.
 

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Discussion Starter #15
FIXED!!!!!!! Finally I found my problem. I had a small air leak on the right side of the carb. The picture is of the small pipe on the right side of the carb. It connects to the hose that runs to the diaphram cover. I sprayed the carb over and over with carb cleaner trying to find the leak. I would occasionally get a tiny raise in rpms, but couldnt tell exactly where it was coming from. I tried to use an unlit propane torch and that finally did the trick on finding the leak. I grabbed the pipe and it twisted left to right fairly easily, so I pushed it in harder with a pair of pliers and done! Instantly idled and runs perfect. Such a tiny thing overlooked and took so long to finally find. Thanks for all the help!







 

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Woo-hoo! Congrats and good job finding it! That's perseverance.



Thanks for the follow up.
 

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Discussion Starter #18
Well, I thought I had all the bugs worked out but maybe not. I was trying to fine tune things a little better today. My pilot screw is about 5 1/2 turns out now. If I screw it in much more, it starts to idle pretty rough. Does that seem like its out too far? Also, when I ride it and start to take off from 1st gear, it has a tiny bit of a miss/hesitation when you first give it throttle. I have a 116 main jet in now. Should I try a larger one? Also I have a #38 pilot jet in. I have a #40 and #42 I was gonna try.
 

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Most folks have luck with 2.5 to 2.75 turns out.



If you had to go 5.5 turns out then it sounds like you are still running too lean for some reason.



The boot from the carb to the airbox can shrink over time and let more air get in at the airbox.





If the bike ran fine in the past with the jet that was in it then something has to have changed.







One of Spudriders photos above









Carb Theory and Tuning







 

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Discussion Starter #20
Most folks have luck with 2.5 to 2.75 turns out.











I tried to go back down to about 2.5 and it ran horrible. It would hardly stay running. I kept turning out and it didn't make a difference until about 5 turns when it smoothed out. Seemed kind of weird to me to have it that far out.
 
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