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Author Topic: Trans Help  (Read 1085 times)

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Trans Help
« on: February 06, 2013, 10:35:04 pm »
I'm posting this up for a buddy who asked for help but we can't seem to figure it out and it's bugging me.

His trans is having problems staying in 4th gear and when in neutral with the clutch engaged (spinning the shafts) and revving the **** out of it (about 6K-7K) it will hit in to gear and bounce back out immediately.

The history on this trans is that it has been ran OEM until 3rd slipped out all the time and then it was back cut.  The bottom end was just taken apart and triple checked.  It was assembled correctly and all clips & spacers on the shaft where assembled correctly in the correct order.

Does anybody know what is going on with it hitting in to gear under high revs in neutral?


My thoughts are: Since the clutch is engaged that the shafts are creating enough centrifugal force that it is pushing the gear in to another gear, the dogs are hitting and it is throwing it back to neutral on the shaft.  If this is happening that means that the forks are either moving to allow the gear to move one way or another to briefly hit another gear OR there is enough play on the drum that the fork can move/wiggle enough to allow the gear to hit against another?

Any serious help solving the mystery wold be appreciated as my knowledge of transmissions is limited.

Thanks

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Re: Trans Help
« Reply #1 on: February 07, 2013, 06:38:55 am »
Was there any grooving on the sidewalls of the shift drum slots?
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Re: Trans Help
« Reply #2 on: February 07, 2013, 08:10:57 am »
Check all the mating surfaces width, the groove on the barrel, the pin and tangs on the forks, the groove the fork rides in. all the clearances are cumulative. Also roll the slide shafts on a glass plate and check the gears for rocking on the shafts, any combination of these together can cause the issues your seeing for the neutral trouble.
Were the forks replaced with the backcut, they usally need to be if theres any jumping out of gear . They get tweaked by a few thousandths and it's not noticable unless installed and moved just rite.
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Re: Trans Help
« Reply #3 on: February 07, 2013, 09:05:06 am »
Quote from: Nopick on February 07, 2013, 06:38:55 am
Was there any grooving on the sidewalls of the shift drum slots?
Guy from what I've been told there is one small spot on the drum where there looks to be a little ware.


Quote from: Iceracer on February 07, 2013, 08:10:57 am
Check all the mating surfaces width, the groove on the barrel, the pin and tangs on the forks, the groove the fork rides in. all the clearances are cumulative. Also roll the slide shafts on a glass plate and check the gears for rocking on the shafts, any combination of these together can cause the issues your seeing for the neutral trouble.

Do you know what the specs are for the pin, the drum grove, the tangs, and the gear groves?


Quote from: Iceracer on February 07, 2013, 08:10:57 am
Were the forks replaced with the backcut, they usally need to be if theres any jumping out of gear . They get tweaked by a few thousandths and it's not noticable unless installed and moved just rite.

I do not believe the forks have been replaced, so just a few thousandths will cause it to slip out of gear even through their back cut?


On a side note my trans when it was back cut has machining on the forks but since I bought the motor with the work done I am not 100% on what they did to the forks.

Thanks for the help
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Re: Trans Help
« Reply #4 on: February 07, 2013, 09:50:18 am »
are you asking these questions for Bfuss, lol
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Re: Trans Help
« Reply #5 on: February 07, 2013, 10:17:07 am »
Fork to grove clear. 10-.30mm fork width4.8-4.9mm, groove 5-5.1mm. The barrel and the tang should be close.  .10mm?? maybe. Should be almost no movement. As its a slow moving part it won't create heat.
 Is there a washer groove in the side of a gear from jumping allowing it to float too much? The list goes on for what to look for. Everything needs to be tight basically.
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Re: Trans Help
« Reply #6 on: February 07, 2013, 12:23:38 pm »
Quote from: GrkGuy on February 07, 2013, 09:50:18 am
are you asking these questions for Bfuss, lol
SSSHHHHH who's that  [|]
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Re: Trans Help
« Reply #7 on: February 07, 2013, 05:06:15 pm »
Look at the wear on the fork fingers, if its uneven this tells all, replace them. I've seen them blue from heat on one finger only. Replace all your springs too, everyone you can find. Make sure your not missing any washers. Look for wear on everything and measure your tolorances acording to your manual.
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Re: Trans Help
« Reply #8 on: February 07, 2013, 08:18:12 pm »
Thanks fellas.  I dropped it off at JH today.  Thinking my backcut job sucked and some other stuff.  Waiting to hear back.
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Re: Trans Help
« Reply #9 on: February 08, 2013, 08:46:36 am »
Quote from: B_Fuss on February 07, 2013, 08:18:12 pm
Thanks fellas.  I dropped it off at JH today.  Thinking my backcut job sucked and some other stuff.  Waiting to hear back.

Well that sucks.  What is this, the third time you have had it apart in the last year?
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Re: Trans Help
« Reply #10 on: March 08, 2013, 07:22:00 pm »
At least the third time.  On the plus side I caught a **** piston skirt this time. So it all works out. 
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