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Thread: DIfferent Carb

  1. #1
    Junior Member jakemistake's Avatar
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    Has anyone ever fitted a different carb onto their TW? Seems there could be quite a bit of improvement in this area.
    When in doubt, Gas it!

  2. #2
    Member Fourcycle's Avatar
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    A fuel injector and ECU for that and spark control would be better thinks I.
    If your only tool is a hammer

    Everything looks like a nail

  3. #3
    Member roadjanitor's Avatar
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    I have been wondering the same thing. My TW (brain dead tonight...think its a 87) carb has gave me fits off and on since I bought it. Clean it out, works fine for one ride. Next time I go out to ride carb is junked up. Blamed rusty fuel tank so bought a Clarke , still same issue. Wondered if a new style TW carb might help solve the problem, or maybe see if I could figure out how to adapt a small pumper carb, maybe something like my DR has......

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  5. #4
    Senior Member TWrider's Avatar
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    the xt225 forum solved the problem by using a TM33mm mikuni pumper....but the guy who sells them (or used to) highly modifies them, he cuts his own needles on a lathe and the cable mounts are custom cnc'd... factory TM's are way off for out little motors...

    http://www.enduco.com/Bike/tm33manual.pdf



    Other than that, Sebastian sells some alternative carbs in Europe at twparts dot com,...but I doubt they are dialed in specific

  6. #5
    Senior Member davidsonsgccc's Avatar
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    this may be a dumb question but do you have a inline fuel filter?
    not a TW owner but i play one on this forum.

  7. #6
    Senior Member lizrdbrth's Avatar
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    Quote Originally Posted by TWrider View Post
    the xt225 forum solved the problem by using a TM33mm mikuni pumper....but the guy who sells them (or used to) highly modifies them, he cuts his own needles on a lathe and the cable mounts are custom cnc'd... factory TM's are way off for out little motors...

    http://www.enduco.com/Bike/tm33manual.pdf



    Other than that, Sebastian sells some alternative carbs in Europe at twparts dot com,...but I doubt they are dialed in specific




    This will prolly start a pizzin contest, but here goes:



    A TW200 displaces 196cc's. (roughly 12 cubic inches.



    Let's say it operated at 100% volumetric efficiency (yeah, right). It's MAX air requirement would be 31 [email protected] 9,000 rpm. In the real world a stock TW prolly only needs about 25cfm.



    A 33mm flatside flows about 100cfm, or 4 times the flow required for a stock TW, and 3 times the flow required for a theoretical "balls out" TW. The flatside also has some behavioral quirks which only make it suitable in certain situations.



    Flatsides are easier to calculate because they have no venturi, but essentially a 33mm carb isn't just slightly bigger than a 28, it's 40 percent bigger.



    It's way more complicated than this, and there's a case for a pumper carb, but few of us will ever be in that situation.



    Just trying to save folks some heartache and cash. The little TK is capable of handling 99% of most folks' efforts to improve horsepower, which generally consist of aftermarket exhausts, airbox mods and rejetting to compensate.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  8. #7
    Senior Member TWrider's Avatar
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    Quote Originally Posted by lizrdbrth View Post
    This will prolly start a pizzin contest, but here goes:



    A TW200 displaces 196cc's. (roughly 12 cubic inches.



    Let's say it operated at 100% volumetric efficiency (yeah, right). It's MAX air requirement would be 31 [email protected] 9,000 rpm. In the real world a stock TW prolly only needs about 25cfm.



    A 33mm flatside flows about 100cfm, or 4 times the flow required for a stock TW, and 3 times the flow required for a theoretical "balls out" TW. The flatside also has some behavioral quirks which only make it suitable in certain situations.



    It's way more complicated than this, and there's a case for a pumper carb, but few of us will ever be in that situation.



    Just trying to save folks some heartache and cash. The little TK is capable of handling 99% of most folks' efforts to improve horsepower, which generally consist of aftermarket exhausts, airbox mods and rejetting to compensate.


    Yes the TK is is the best carb for a stock 200....the poster asked about DIFFERENT carbs, the 225 may have more cc's but the head, ports and valves are nearly identical to the 200. The xt225 guy was using the pumper carb for better OFF ROAD throttle response for where the xt tk "CV" carb lacked in certain off road situations....I agree about air flow efficiency problems, a 4valve 250-350 really wakes up with the 33 pumper, and many aftermarket houses use it. As I stated the carb was MODIFIED for use on the 2 valve 225. An off the shelf unit will not work.

  9. #8
    Senior Member lizrdbrth's Avatar
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    I agree. Like I said, it's way more complicated. But I'm sure whoever's selling the 33 conversion is laughing all the way to the bank at the thought of how many people are buying his kit without putting in the extra work and expecting to bolt on horsepower when all they're really getting for 600 bucks is snappier throttle response. I don't want this happening to our TW brethren. Bigger ain't neccessarily better in our case.



    All kinds of people read this stuff, and I'm not suggesting that you, or the original poster didn't "get it". I think it's important to explain that the advantage of the pumper carb is the pump, and that extra 5mm ain't doing a thing for ya.



    Therefore bolting on a conventional carb of 36 or even 50mm won't do a thing for ya, so don't chase it. As long as it's jetted properly your motor is only gunna take as much air as it needs. For a carb to be "better" in our case it needs to bring something else to the party, like an accelerator pump, better fuel metering, overlap or altitude compensation, or jet availabity depending on what you're after.





    I'm not saying playing with carbs won't have any value. If you want a flatside the smallest commonly-available item with a pump is a 33. What I'm saying is a 28 with a pump would do the same thing on our motors. Different brands and types of carbs all have their advantages and disadvantages, I'm just trying to explain why bigger alone won't neccessarily change anything. Since the 33 came up, and this is a carb discussion I'd like to dispel the myth about size because it's a common misconception. Humor me.



    For the benefit of those less dweeby than I, I'm gunna risk an analogy:



    Let's say that we as average humans are standing at sea level, and the earth is an infinite source of unrestricted air.



    Our lungs have a given capacity (displacement}. No matter how blessed you may be, no matter how big your mouth (carb) and airway (intake tract) are, you can't take in more air per breath than your lungs (cylinder volume on the intake stroke) can handle. As long as your mouth isn't sewn partially shut (UNDERSIZED carb to begin with) most of us have an oversized "carb" from birth. Steve Tyler is prolly capable of 1,000 hp. But I digress.



    Now let's train for a marathon and increase our lung capacity (boring, stroking, headwork, cams). If you're the poor guy born with his mouth partally sewn shut, you're gunna need surgery (a bigger carb). But the rest of us will still be fine because we had a sufficiently oversized "carb" to begin with.



    Up to a point, that's a TW. All i'm sayin' is that I'm not sure you'll need a bigger mouth with typical mods.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  10. #9
    Member roadjanitor's Avatar
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    Bought a couple of the brass sintered (SP) type from Rocky Mountain. Should have taken care of most of the junk one would have thought, especially after I rinsed out the new Clarke tank, put on a new filter, and did a full tear down, wash and blow (even used a small piece of electric wirein each hole)of the carb. Bikes got 5600 miles on it so I wouldn't think carb was way wore out, but could be wrong. I figured the DR carb wold be too big but wondered if there might be something out there more suitable. I will continue the battle to sort this out for a while longer, maybe watch for a carb off a fairly new bike, maybe even look at a brand new carb. At some point I may have to cut my losses and part it out, but I really hate to. Had too much fun on the couple rides when it ran good...............

  11. #10
    Senior Member Mr. BigWheel's Avatar
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    [I put a TM33 on my BW350. I know it's comparing apples to oranges, but the improvement is incredible. The accelerator pump makes a tremendous difference in response and the starting and idling characteristics are worlds better. The BigWheel has a butterfly carb that is unsupported by it's manufacturer and most are worn out at this point and untuneable.



    That being said, there were numerous complications that needed to be resolved.



    The carb is too tall and the interferes with the gas tank and cdi. The slide is actuated from the opposite side of the carb which complicates cable routing and causes interference with the kickstart lever. It requires new fuel hose routing due to the pickup's location being different.



    It needs to be tuned to the engine, which is an exhausting process.



    All in all, I found it to be a worthwhile project, but it was certainly more complicated than I expected. It may not be as complicated on the TW but there will definitely be unexpected difficulties. If you enjoy the process, it can be very rewarding or it can be utterly frustrating. Or possibly, both.



    Regards,



    Mr. BIgWheel

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