Looking for better MPG
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Thread: Looking for better MPG

  1. #1
    Junior Member iacfi's Avatar
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    Aug 2015

    Looking for better MPG

    Hi Everyone,

    I am a new owner of a 98 TW200. I live in Anchorage and I was simply looking for a reliable, cheap, and efficient commuter bike in town. The TW200 was pretty far off my radar, but when I saw the bike and the price I realized it was a good fit for me. I got my license 7+ years ago and hadn't ridden since I bought the bike. This bike has been super easy for me to "re-learn" on. I am definitely enjoying it, and although the bike has about 6700 miles, it is running great.

    My only disappointment has been that the bike doesn't seem to be getting very good mileage. I have only filled it up a couple of times, but it seems to be getting around 40-45 MPG. I am driving in light city traffic, mostly going 40-50 MPH. It still has the knobby tires on it. Even with the city traffic and knobby tires I expected better MPG.

    The previous owner said that he replaced the sprockets in 2012. He also said that that the carb was rejetted, the intake/exhaust was opened up, and he installed a washable air filter. He also said something about "high flow" and that it runs a bit rich causing the carbon build up on the plug at times.

    I understand he did some of this work to increase the top speed. I am a pretty tame rider. I don't take the bike on the highway so I would much prefer to have better MPG than a fast bike.

    Any recommendations? Would replacing the jet make a significant difference? Or is my poor MPG more due to the knobby tires and city traffic?

    Thanks for any help you can offer.


  2. #2
    Junior Member iacfi's Avatar
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    Aug 2015
    By the way, I am 150 lbs and am driving on mostly flat terrain (no significant hills). I have never had the bike much over 50, but it seems to have plenty of power left at that point.

  3. #3
    Super Moderator littletommy's Avatar
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    Mar 2013
    Spokane, Washington
    The previous owner said that he replaced the sprockets in 2012. He also said that that the carb was rejetted, the intake/exhaust was opened up, and he installed a washable air filter. He also said something about "high flow" and that it runs a bit rich causing the carbon build up on the plug at times. Quote]
    __________________________________________________ ___________

    Count the teeth on the sprocket, stock is 14 front 50 rear. Not sure what he means when he said he opened up the intake and exhaust, you should check to see that the valves are set correctly. He probably does not have the carb jetted correctly, something's too rich. Check to see if the air filter is clean and lightly oiled. Give it a tune up by the book first. Even with modifications, you should probably be getting around 60+ mpg.

    Welcome to the forum Jim. We'll do our best to help you.
    Last edited by littletommy; 08-07-2015 at 01:49 AM.
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  5. #4
    Senior Member Tinybear's Avatar
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    Apr 2014
    SW Ontario
    My bike has a aftermarket exhaust and higher flow air filter and is jetted accordingly. When commuting on the bike it's all city streets under 80kms/hr.

    Because I use my bike on trails it will always have knobbie tires. I do tend to be heavy on the throttle as I'm 6' 260ish lbs. And my bike still gets me anywhere from 55+ mpg (my last tank netted best yet at 71mpg)

    Being as you state your bike sat for some time and with the crappy fuel today you may want to clean your carb and do a good tune up. Also maybe look into changing the gearing out for stock in the future.
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  6. #5
    Senior Member jtomelliott49's Avatar
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    Sep 2012
    Wichita, KS
    This may sound silly, but check to make sure the choke/enricher is pushed in, and not pulled out.
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  7. #6
    rbm is offline
    Senior Member rbm's Avatar
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    Jan 2011
    Hello and welcome! The above recommendations are a good place to start. As well, I would add a god dose of Seafoam to the gas and let that work in the carb since it had been sitting for a while.
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  8. #7
    Senior Member scotti158's Avatar
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    May 2013
    Groton, NY
    With it jetted correctly, valves adjusted and engine running the way it should, 65mpg+ should be reached easily, even with (properly inflated) knobby tires.
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  9. #8
    Senior Member sponge's Avatar
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    Apr 2015
    Mesquite Nevada
    Jetting the carb back to stock will help no doubt. I jet rich because I live in the crazy hot and rich jetting runs a little cooler. Come winter I may go back down to stock to get better range. I have also noted about 5 MPG difference from just tire pressure. If you are mostly city you can go up to the max 22 front, 25 rear.
    Last edited by sponge; 08-07-2015 at 10:12 AM.
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  10. #9
    Super Moderator Purple's Avatar
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    Mar 2015
    Ynys Môn
    TW's come with a washable (oiled) air filter as standard - treat any thing he has said with a pinch of salt

    Sounds like he was trying to make the bike do what it's not designed for - go faster

    Any changes to the existing standard exhaust will make no difference, you'll need a completely new set-up to do that - so that's another one you can ignore ("if" it still has the standard exhaust)

    As said above, simply change the jet back down to what the bike is designed to run on - until then, rich is better than lean

    Not sure how much this will improve the mpg - a little perhaps - more to do with the condition of the engine ........

    A word of caution - take it one step at a time, and prove that each step works - take notes ......... you need to be able to reverse anything you do that compromises the running of the bike

    The previous owner has fiddled about in there and you don't know what he's done - tread gently .......

    (And welcome to the board)
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  11. #10
    Senior Member Turtle Chaser's Avatar
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    Aug 2010
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    Sounds like great advice so far. My '06 motor is completely stock and I get 60-65mpg on my 44 mile commute. My gearing is 15/50 (non stock) as I am running @ 60mph most of the commute. Mine is a California version originally jetted very lean and ran poorly. I went up a size or two on the main jet, raised the needle and adjusted the mixture screw and it now runs way way way better. Tdubs are very sensitive to carburetor tune so keep checking your spark plug until you get a nice light tan color. Sounds like you are running rich and that explains the poor mileage. I think there are some carb tuning threads/stickies here.

    best regards, MAC

    P.S. also you could check your float level. I need to do this myself!
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