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TOPIC: DT250 E sometimes miss 3rd and 4th gears

DT250 E sometimes miss 3rd and 4th gears 03 Aug 2017 18:37 #1

  • indybp57
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I have an issue with my DT250E. Sometimes when shifting up into 3rd and/or 4th, I hear the "clack" that sounds like it went into gear, but it doesn't and when I roll on the throttle and let out the clutch of course the engine revs like it's between gears. I shift again and it goes right in. This happens maybe 20% of the time. I've tried holding the shifter up until I release the clutch but it doesn't seem to matter. No problem with 1st, 2nd, or 5th, or downshifting into any gear. I'm pretty well versed with everything mechanical except a bike transmission. If I split the cases what am I looking for? Any help is appreciated.

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DT250 E sometimes miss 3rd and 4th gears 03 Aug 2017 20:03 #2

  • RT325
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Not easy to diagnose that one without going in there as is an unusual problem.
www.partzilla.com/parts/search/Yamaha/Mo...+CAM+FORK/parts.html
I wonder if it's broken one of the pins No2 relating to 'that' gear but on second thoughts that doesn't pan out as you say two gears [two broken pins--i doubt it]. Had something similar in my very early 360 where the stop bolt was bent. Is an off set adjustable bolt in my case [RT2 360] but i'd arsed off on the concrete & bent [the bent or offset] screw from where it was set to give equal movement for up & down shifting.
www.partzilla.com/parts/search/Yamaha/Mo...IFT+SHAFT/parts.html
So from that point of view check No8 in the second link. I'm surprised it shows a pin or dowel & not an 8mm threaded stop. If all looks ok then check the small spring & claw arm 21 & 20 in the first link. After all that & if all is ok then damn it you'll have ta go in & check the dogs & selector as same selector runs 4th & fifth on the main shaft. Actually i've cocked up as you say 3rd & 4th so that's two different selectors. 3rd is on the output shaft & 4th on the main shaft. Don't get confused by the diagram calling the gears in a different place. You want the sliding gears & the dogs on those gears & the dog slots they slide into [get round edged & kick back out rather than grabbing & holding but once fully in can be good enough to hold [till it gets worse]. Hope you can follow all that rambling--not sure i can lol. ps, Plunger & spring ok underneath
, can't see that playing up without doing so in all gears.

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DT250 E sometimes miss 3rd and 4th gears 03 Aug 2017 22:00 #3

  • Makotosun
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Before you go splitting the cases, Make sure parts 10-13 are installed and in good working order. If the spring is missing (common problem) it will miss gears and or pop out of gear. Had I caught this, I would have saved a full tranny rebuild!

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DT250 E sometimes miss 3rd and 4th gears 04 Aug 2017 03:55 #4

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I second checking for parts 10, 11, 13. I just had a very similar problem with gears being hard to find and popping out of gear as well. All solved by installing a missing shift drum detent and spring
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The Oil burners: 1973 DT-250, 1966 YM-1 305, 1966 YSD3, YZ-105
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DT250 E sometimes miss 3rd and 4th gears 04 Aug 2017 17:14 #5

  • indybp57
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Makotosun wrote: Before you go splitting the cases, Make sure parts 10-13 are installed and in good working order. If the spring is missing (common problem) it will miss gears and or pop out of gear. Had I caught this, I would have saved a full tranny rebuild!


I'm assuming those parts are accessible from outside the case? Maybe on the bottom?

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DT250 E sometimes miss 3rd and 4th gears 04 Aug 2017 17:56 #6

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Yes , accessible from under engine . # 13 looks like a drain bolt , but has a screwdriver slot in it .
Possibly round rather than hex head . Sometimes mistaken for gearbox drain bung .

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DT250 E sometimes miss 3rd and 4th gears 04 Aug 2017 18:08 #7

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i'd expect it to look like this & have a 12mm hex & be sitting on an angle on the left side roughly straight down under the sprocket area.

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DT250 E sometimes miss 3rd and 4th gears 14 Mar 2019 09:16 #8

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It only took me 1.5 years to get around to look at this. What I found is that one of the previous owners had stuck the cam follower #10 into the bolt #13, then stuck the spring #11 into that. So the blunt end of the spring was acting as the cam follower, but had gotten bent and wedged up around the cam. Luckily the spring is still available, the cam follower is not, but it is still in good condition. Thanks for everyone's comments.
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DT250 E sometimes miss 3rd and 4th gears 14 Mar 2019 13:17 #9

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That's a first for someone to do 'that'. Thanks for the update & great that you found it without having to pull it right apart.--well hope you didn't pull it apart.

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