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Yz250 false neutral in 5th gear after full rebuild

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So my mechanic just rebuilt my 07 250, crank, bearings and seals. Now the bike runs awesome 1-4 but when I get into 5th it's slipping out and hitting a false neutral where the bike will just free rev and stutter. I literally just broke in the bike and I found this problem now. It didn't do it before the rebuild which is why I'm wondering if it's a freak thing. If I hold up on the shifter when I'm in 5th it doesn't do it. I just think it's shitty I have to split the cases not even 2 hours on a full rebuild. The guy who did my bottom end said everything looked good but when he was bench shifting it 5th was a little iffy but it should still work. He's been a mechanic for 50 years one of the best in my area. So I'm not sure what to do. I just wanna ride it's been 3 months since I've rode

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Make him tear it apart and fix it, you paid good money to get something fixed and shouldnt have to deal with paying extra to fix what he screwed up

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Make him tear it apart and fix it, you paid good money to get something fixed and shouldnt have to deal with paying extra to fix what he screwed up

I'm 90% sure he wouldn't have split cases and rebuilt a motor if he thought something needed replaced. He told me throughout the build stuff I should replace and stuff that was fine. I'm sure he would be willing to fix it but I'd rather do it myself this time. I could have done it just don't have a clutch holder or anything

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  It doesn't take much for that tranny to start slipping.  Had it happen few times when I raced those. Usually 2nd and 3rd for me one time 4th . If dogs are just alitte rounded it slips and just gets worse.  You really have to inspect that tranny good when apart.  I'd he's done for 50 years take it back maybe. 

Edited by Motox367

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Maybe forgot a washer on the 

clutch shaft or sprocket shaft ?

Even the best mechanics can

make minor mistakes once

in awile. 

Grab the sprocket and clutch 

and move them left to right to

see how much float there is. 

Not sure what the actual spec 

in the manual is, but usually

.008" to .012", maybe even as

much as .020". The washers are

usually a standard thickness size,

1mm, 1.5mm, 2mm, so if there is

excess play, that might be the

problem

Check the 07 Yz 250 transmission

microfiche, to see if washers go on

the trans shafts between the gears

and bearings in the cases, and 

between gears on the shafts

Edited by yamaha7654

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Yamaha puts thrust washers on the gears and if they didn't fall apart when he split I wouldn't think the inside washer would fall off but never know.  50 years you'd think he knows that I sure does. I've done them for almost 23 years and I know that. You check for thrust washers stuck to bearings soon as split. Or could fall off and not know.  But with that tranny idk. Check your shift mechanism and segment for wear or something messed up there. If not I'll bet you'll find rounded edges on pinion gears and wear spot on one maybe two forks. That's my geuss anyway 

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C1 fork usually wears more than the other 2 (L-R) or fork 2-3 in diagram. Since 5th wheel has a specific fork, and I have had a bad R fork (5th) before it could be that shift fork (3 in the diagram) is bad on the fingers. A combination of the fingers and slightly rounded doggs will slip, and since you are holding it in with your foot, I'll bet the fork was marginal and should have been replaced. 

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I work at a Yamaha dealership and the head mechanic is the one who did it. He said if I would have told him it was doing that before the build he would have known to fix it. But I do get parts cheap and can order them in so what would you recommend ordering before I tear it apart. And will it do much damage to ride just 1-4 gears? I do mostly single track don't need 5th too much

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3 minutes ago, BTYZSquad said:

I work at a Yamaha dealership and the head mechanic is the one who did it. He said if I would have told him it was doing that before the build he would have known to fix it. But I do get parts cheap and can order them in so what would you recommend ordering before I tear it apart. And will it do much damage to ride just 1-4 gears? I do mostly single track don't need 5th too much

I'd wait till you split never know. Any sign of rounded chiped coggs on pinion gear and gear wheel it meshes and replace.  These trannys are sensitive you gotta check every yz250 closely. :ride: goodluck :thumbsup:

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I wouldn't order anything until I gave it a good inspection. Honestly, if you are holding it in 5th with your toe and it works, I think its the fork. There are no outer washers on the shafts like Honda.

If you are not using 5th, I would say no it shouldn't hurt to ride it becase the 1-4 forks are doing all the work. But I would definitely get to it asap (as time permits, you want to ride.) 

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Most likely gonna give it a month or 2. I haven't rode in 3 months bike feels too good to tear apart again lol

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