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drive train issue with '89 yfm 250 moto-4

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Old 06-01-2009, 08:58 AM
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Default drive train issue with '89 yfm 250 moto-4

hi all, with the help of 91warrior357 i got my moto-4 running over the weekend. thanks man. now on to the newest issue. i noticed when i put it in gear and give it gas, theres what seems like a very long pause in the drive train before it actually moves. just when it starts moving, it jerks the machine really hard, as if it were a chain drive with a REALLY loose chain. it does this in both forward and reverse gears. the opposite is true when you back off the throttle. this thing has a drive shaft instead of a chain. could it possibly the the u-joints? can the u-joints be inspected without tearing half the machine apart? or, is there something else in the drive train that tends to go out in these things? as always, any and all help would be greatly appreciated.
 
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Old 06-01-2009, 02:13 PM
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it does look like theres a u-joint that goes on the yoke, that could be where the problem is, i would slide something under the back end of the atv so the rear wheels are spinning and try to see and listen to it when it goes in gear and see if u can tell where the problem is, you should hear a thunk or something, or at least if the u-joint is worn id try to wiggle it and see if it actually is worn.

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Old 06-01-2009, 02:32 PM
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Once again, great idea. lol I'll do that when i get home and post the results later this afternoon. thanks
 
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Old 06-05-2009, 07:28 PM
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ok, i just dropped the swing arm on this thing and sure enough the u-joint is toast! i have a new one, the question is, how do i remove the old one? there must be a trick of some sort. i've already removed the c-clips that hold the caps (or whats left of the caps) in. now i just gotta figure out a way to remove the caps. any ideas?
 
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Old 06-05-2009, 08:46 PM
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Originally Posted by mdlearnest
ok, i just dropped the swing arm on this thing and sure enough the u-joint is toast! i have a new one, the question is, how do i remove the old one? there must be a trick of some sort. i've already removed the c-clips that hold the caps (or whats left of the caps) in. now i just gotta figure out a way to remove the caps. any ideas?
Either a press, or an appropriately sized socket driven by a "B-flat masher" (Hammer) is how I do U-joints. It matters whether you can remove the associated part or not, from said vehicle....
 
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Old 06-05-2009, 08:48 PM
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Originally Posted by Terrellster
Either a press, or an appropriately sized socket driven by a "B-flat masher" (Hammer) is how I do U-joints. It matters whether you can remove the associated part or not, from said vehicle....
yepper same way i do them.
 
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Old 06-05-2009, 09:25 PM
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got it! went to lowes and picked up a $20 air hammer, found a bucking bar in the tool box, got the wife to back me up, and blasted away. they didnt even stand a chance! now after all that, the u-joint the yamaha dealer sold me is the wrong size. go figure lol thanks for the advice guys.
 
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