Yz250 1st gear issue help needed ?

Andy86
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Andy86
Edited Date/Time 5/24/2016 3:43am
Hi all, having a little problem with 1st gear on my Yz250 1987 model

The engine has just been rebuilt completely new clutch, crank and 95% of the gearbox replaced

If i try to select 1st from neutral it grinds when letting the clutch out the rear wheel locks up and the shifter lever locks up too, kicking the engine over releases the locked up shifter and rear wheel

With the clutch in 1st gear engages no problem as soon as i let the clutch out it starts grinding

Yet if i ride the bike setting off in 2nd and go up through the box to 3rd, 4th or 5th and then come back down through the box and into 1st gear with the bike free rolling then 1st gear works no problem at all without grinding it stays engaged

All other gears work fine and so does the clutch

3 new shift forks, shift shaft and shift drum have all been replaced

And everything was assembled as per the clymer manual

The picture in my profile pic is the engine in question

Any thoughts on the problem before i split the cases again to investigate the issue

Any thoughts, advice is appreciated
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xnationalwrench 5/20/2016 7:05pm
5/20/2016 7:05pm
Sounds like you need to split the cases, either you added or left out a shim or a bad shift fork or a bent shift fork shaft
Andy86
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Andy86 5/21/2016 5:03am
5/21/2016 5:03am
xnationalwrench wrote:
Sounds like you need to split the cases, either you added or left out a shim or a bad shift fork or a bent shift fork...
Sounds like you need to split the cases, either you added or left out a shim or a bad shift fork or a bent shift fork shaft
Thanks for the reply mate i'll bear the info in mind

Anyone else got any other ideas?
Andy86
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Andy86 5/23/2016 1:09pm
5/23/2016 1:09pm
Nobody else got any ideas?? i thought vital had a wealth of knowledge
cwtoyota
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cwtoyota 5/23/2016 6:49pm
5/23/2016 6:49pm
Andy86 wrote:
Nobody else got any ideas?? i thought vital had a wealth of knowledge
Drain the oil and the coolant, then pull off the clutch cover and the clutch basket.

Check the shift stopper (it's the part with a roller on it) and the star shaped wheel. That star wheel has an alignment pin that times it with the shift cam. Make sure the star wheel isn't damaged and that it is properly timed with the shift cam.

More than likely, Xnationalwrench is right and you have something wrong between the cases. That could be a bent or damaged shift fork, a shim or clip installed incorrectly, a busted or incorrectly installed gear, or some other issue.

An important thing to check is that the shift forks, their guide rods and the corresponding bores in the case halves are in good shape.

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Andy86
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Andy86 5/24/2016 3:43am
5/24/2016 3:43am
cwtoyota wrote:
Drain the oil and the coolant, then pull off the clutch cover and the clutch basket. Check the shift stopper (it's the part with a roller...
Drain the oil and the coolant, then pull off the clutch cover and the clutch basket.

Check the shift stopper (it's the part with a roller on it) and the star shaped wheel. That star wheel has an alignment pin that times it with the shift cam. Make sure the star wheel isn't damaged and that it is properly timed with the shift cam.

More than likely, Xnationalwrench is right and you have something wrong between the cases. That could be a bent or damaged shift fork, a shim or clip installed incorrectly, a busted or incorrectly installed gear, or some other issue.

An important thing to check is that the shift forks, their guide rods and the corresponding bores in the case halves are in good shape.
Cheers bro the shift star is welded in place by the factory its a stupid design once the bearing wears out you have to replace the entire shift drum

All 3 forks, the rods and the shift drum all got replaced for Nos items

What confuses me is the fact that its an intermittent fault as explained in my first post surely if i had a shim or washer installed incorrectly the gear would not work at all ?

I made the post in the hopes someone else had experienced a similar issue and could point me in the right direction

Thanks for your reply mate its appreciated

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