My first night of wrenching. Opinions welcome
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  1. #1
    Senior Member silverhead's Avatar
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    I made myself familiar with the bike tonight for the first time. I bought a new NGK plug and gapped it at 0.65mm. Valve lash was inspected at TDC and was found to be intake: 0.004mm, exhaust: 0.006mm. The timing chain lines up with T and TDC and has tension. My bike has 3800 miles indicated on the odometer and seems to be about right. My carburetor boot was found to be chipping off that rubber material from the metal part. I pulled the carburetor and completely cleaned it. I pulled all the jets and choke parts and cleaned all passages with piano wire and carb spray. The carburetor looks great. 40 pilot and 114 main jet. Pilot screw is turned out 1.75 turns from bottomed.







    OK, so my problem is that the bike doesn't like to idle. It starts right up on choke, but the engine runs way too fast. When you turn off the choke, the engine runs poorly. Giving throttle makes the engine race. This leads me to believe there's an air leak. I coated the intake boot with clear nail polish to seal it up. I also sprayed carb cleaner around the intake boot while the bike was running and it had no effect on how the bike ran. I used a timing light to check the ignition to make sure it was firing every time, and it is.



    So, I'm a bit stumped, but how likely is it that my intake boot is shot? It seems solid, but the cracking bothers me.



    I made a video of the bike running and am looking for any opinions about what to do next.



    http://www.youtube.com/watch?v=Nwb7eOzxesY





    I wanted to shim my needle, but I couldn't figure out a safe way to remove the slide. This video ( youtube video shows the same type of carb as mine (pre 2001) but mine is not identical inside where the slide exists. Mine has a metal linkage and springs and crap in there. Is there a simple way to free the slide so I can get at the main jet needle to shim it?
    1993 TW200

  2. #2
    Senior Member B-dub's Avatar
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    Take another look at the valve clearance specifications. My manual says .05mm to .09 mm or .002 to .004 inches on the intake, and .11mm to .15mm or .004 to .006 inches on the exhaust. I think you're confusing the mm and inch specifications.
    My handle is B-dub, I ride a T-dub, and drive a V-dub.

  3. #3
    Senior Member silverhead's Avatar
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    You're correct. I meant inches.



    Anyway, the old 'carb spray' around the intake boot didn't yield any difference in the way it ran.. Meanwhile the pilot circuit is clean and clear and the screw is set right (has the spring and everything.)



    I'm stumped.



    I need to find an adapter so I can pull a compression test on the engine. The plug is white, so it's definitely lean. The plug I removed was black, however...



    The mission continues.. It's nice out today.



    Even though the part numbers differ due to the tube that sticks out of it, can you run a 2001+ carb joint (intake manifold, boot, what have you) on the older bikes or did the size of the carb change?



    The newer part is much cheaper.
    1993 TW200

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  5. #4
    Senior Member mhomadness's Avatar
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    Don't mess with that old boot. Replace it. If the rubber is in that kind of condition, you may not have a good seal where the throat of the carb clamps inside the boot. This can cause lean run conditions that are difficult to detect. I would recommend replacing the intake boot, Check the valves again (per B-dub) check your air filter if you have not done so already. The important thing is to eliminate the questionable intake boot, and then you can go from there. m.

  6. #5
    Senior Member mhomadness's Avatar
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    I don't know if you can use the newer intake boot...



    That 114 jet makes me wonder too. First though, you must take the boot out of the picture. Then you will have a better place from which to go. m.

  7. #6
    Senior Member silverhead's Avatar
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    My dealer discounted me on the boot.. 55 bucks, so I ordered one.
    1993 TW200

  8. #7
    Senior Member mhomadness's Avatar
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    Lot's-O-Munny, but well worth it! m.

  9. #8
    Senior Member silverhead's Avatar
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    I did a lot of little things today. I'll start by saying the bike still runs exactly the same (badly, really lean.)



    I'm pretty sure my intake boot is sealed, but I can't be certain. I can't believe it leaks enough air to cause the problems I'm having.



    Things I did:



    1) Set cam chain tension by the book (0.5mm on the adjuster rod)



    2) Set float height to 27mm (it was set at 24mm)



    3) Reassured myself the pilot circuit was clear



    4) Made shims for the needle (three, or about 1 click higher on a Mikuni needle)



    5) Pulled a compression test (160 psi which is higher than max specification??)



    The bike runs exactly the same with surging on throttle, running very hot (I could tell the exhaust header was way too hot way too fast)



    Here's how it started after I did all of this stuff:



    http://www.youtube.com/watch?v=HB7PVXrfzIo





    Photos from today:





    Clean carburetor









    Float height setting (I set my floats at an angle like this to engage the needle spring about half way)









    Pilot jet re-examined and cleaned









    Slide and needle look fine. No scratches to let air past the slide. Needle isn't bent.











    Shims I made out of pop tabs for the needle







    I cut a rubberized gasket just for good measure at the intake joint/cylinder mounting point.







    Compression when hot.. What could cause it to be higher than 150psi? I checked it with two different gauges, both registered 160psi (throttle open, using the starter)







    This is what the plug looks like after what little riding around I have done. I don't want to cook the exhaust valve. The tip is white and crusty.









    I'm trying to cover all my bases. Can you actually set ignition timing on the bike? I haven't looked at that yet. I probably will check it to make sure it's not too advanced.
    1993 TW200

  10. #9
    Senior Member mhomadness's Avatar
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    OK, if you have not read this thread yet, go here: https://tw200forum.com/index.php?/topic/647-carb-tuning/



    I am suspecting the main jet. The 114 is the stock jet, and you would think that stock should be good / correct. However, my engine is stock, low miles, and when I got the bike (used) I replaced the carb, as the original was beyond reasonable repair. I was having similar problems as you are having, I did shim my needle, and went to a larger main jet, a 118 if I remember correctly, & that fixed it. Don't let it get you too crazy until you get the new boot. And you may want to try a lager main jet, IMHO. m.

  11. #10
    Senior Member silverhead's Avatar
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    Typically the main jet doesn't set in until you're at 1/2 - 3/4 throttle, correct?



    At least that's how a Mikuni (which I'm much more familiar with) works.



    ie: pilot jet is the only one working at idle unless RPMs are high enough (like in this case) to suck up some gas from the main circuit. The boot should be here by the end of next week. I stuck it on a rubber block and pulled vacuum on it and it was holding pretty steady. I still think it's sealed.



    If the main jet and the boot are fine, what other things can cause this in terms of mechanical problems with the engine? I'm trying to figure out if someone else screwed the bike up and dumped it to the previous owner, and then to me ;-)



    I just get impatient when dealing with something as simple as a lawn mower and I can't figure it out, haha. I sprayed carb cleaner around the boot, the plastic cap over the slide, and around the head, looking for a change in the way the bike runs to find the leak and didn't turn anything up.



    114 is the factory OEM main jet and 40 is the factory pilot jet. I live at 1000 feet and typically bikes 'run OK' at factory settings here.
    1993 TW200

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