My Tw Has Strange Power issues. Slows down on highway and speeds up at random.
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Thread: My Tw Has Strange Power issues. Slows down on highway and speeds up at random.

  1. #1
    Junior Member FurnaceDoc's Avatar
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    My Tw Has Strange Power issues. Slows down on highway and speeds up at random.

    I got my tw200 last year to learn and have fun on both the street and the trails. Its a 1998 model. It worked fine for about 2 weeks after i got it, after that its been constantly losing power, at all speeds, but really noticeable at highway speeds, i'll be doing 90 with the ability to take it up to 100 (Maybe a little more) but all of a sudden it will cut the speed down to 80 or less, sometimes I have to give it everything it has just to keep it at 80... Sometimes it will bog down to 80 for 10 seconds then fire back up to 90, sometimes it will stay at 80 for 10 mins... Sometimes it starts with this slow issue then clears up for a bit, sometimes it starts perfect then starts slowing down after a bit of riding.... getting scary to drive now. Got this thing for its ruggedness, but its been nothing but problems for me. I've changed Coil, Spark, Pulled off Carb (Like Brand New), Tightened Chain, Checked fuel flow from tank. Screen On Tank. Bikes in very good shape, I want to fix this but seems like im changing everything on the bike, now im looking at a new battery (sometimes this causes issues even though It can start itself on battery. Im assuming its the original battery) or the Cdi box. Would like to buy another bike next year (never buying used again, what a nightmare this has been) and not sure if trying to fix this is even worth it. Anyone have this issue before... ive searched the forums, im down to the battery/cdi. All I want to do is ride my bike but at the same time I dont... this really really sucks. Had to be my first bike, i never seem to catch a break. Can't even do my M test next year unless this is fixed. I want to take it to a shop but whats that gonna end up costing me? & If I get a crappy shop nothings gonna get fixed anyway. Would they be able to do tests on any of this stuff, or will they just be part swapping like me? Cause I can do that myself.
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  2. #2
    rbm
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    First off, just for clarification, please confirm you are reading KPH and not MPH . It's not the battery. Could be the CDI, not likely as they rarely fail. When it happens, immediately pull over and open the gas tank to see if it "sucks" air, could be a blocked vent. Also, check the foam on the seat pan that seals the air box, if it's wonkey or missing it could cause this issue.
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  3. #3
    Junior Member FurnaceDoc's Avatar
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    KPH and i'll go do that right now, thanks.

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    Junior Member FurnaceDoc's Avatar
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    Just removed the air box cover, foam seems like its where it should be, its in really good shape too. Drove down the road for a little bit, it seemed to be slow the whole time. Bouncing between 80 n' 90 but not really getting its power back at any point in that short ride. When it gets/loses power it happens fast, like instantly ill be forced to that speed, kinda like pulling back the throttle hard. It is not a slow happening, its instant POWER or Half Power. I dont want to be doing 90 behind someone not paying attention and have my engine die out to 80 or less because im not holding the throttle at full when its running properly. Pulled off the gas cap anyway but diddn't hear any suction at all.
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  6. #5
    Senior Member kelly b's Avatar
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    Check the rubber "snorkels" that connect the carborator to the air box and cylinder head. They shrink over time and cause just what you describe.
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  7. #6
    Junior Member FurnaceDoc's Avatar
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    They are the original hoses, i changed one last year because it was awful looking, The rest are hard as steel. I'll replace them and test it. Not sure where i put my extra hose, might take me a while. I'll post results. Thanks.
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  8. #7
    Super Moderator littletommy's Avatar
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    Get an old timing light, hook to the battery and spark plug, tie down the trigger, mount it on the bars or somewhere you can see it flashing and go for a ride. If the flashing breaks up or stops during the episode, most likely it's the CDI. And if so, are there any riders near you that you could swap CDIs for a bit to verify?
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  9. #8
    rbm
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    Do you have fresh fuel in it?
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  10. #9
    Senior Member SportsterDoc's Avatar
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    If the fuel tank is not venting, it will affect fuel flow, which may appear normal, with engine off or at idle speed.
    When it is struggling, does it hiss when cap is loosened?

    Just one possibility
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  11. #10
    Junior Member FurnaceDoc's Avatar
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    I checked the hoses, I thought you meant the little tubes under the carb when i first read that but then I checked the bigger hoses connecting to the carb, they are flexible and in good shape. Went for another 20 min ride n' was still sluggish around 80 to 90 until right when i was getting back its like it kicked into turbo and went up to 100 plus no problem. This was on a long flat run, no hills, just kicks in like it was missing something. This problem has been constant since last year, i've always put premium in the tank and i've used seafoam a few times just to be sure. I was told Shell is the only gas station that has no ethanol in its premium. Could this be an issue? I've been getting mine from esso, and a few other places just to see if gas was the case... I don't have a timing light and kinda live in a small town, no other tw's, i've never really been able to go very far on the highway, having a top speed of 80 (at times) is brutal and takes all the fun out of it for me if any other vehicle is behind me. Cant ride with anyone else in this condition, cant do my test. Kind of embarrassing too. Might take it to a local guy once to see if he can figure it out, if not i'm gonna have to give up, with all the extras and parts i've had to put on this thing plus the initial cost and extra issues im basically at half the price of a new one... should'a got the new one.
    Ken likes this.

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