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YZ250 2007 complete rebuild - transmission help

By nath125,
in Yamaha 2 Stroke

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nath125

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Hey guys,

 

So Ive looked on the forum and some other for a heads up with the complete rebuild of my YZ but man I am having trouble re-seating the ytransmission.  I have managed to put it in, all looks flush and in place.  Cogs spin freely but I cannot rotate the cam at all to see if the shift forks are working.  Should I be able to move them?

 

Ta,

 

 

Nath

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Theo

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When I did that on my YZ, it was hard to move the cam and the forks, but it was possible provided I "helped" the fork and the gears with my hand. If the dogs are misaligned, the fork won't be able to move.

Besides, when the gearbox works with the engine assembled:

- it's soaked in oil,

- the two crankcases keep everything aligned,

-the shift lever provides leverage.

When you test it by hands you only have one side keeping things aligned. I also dislike the idea of applying much oil to those components because, if they drip with oil while the cases are joined with the liquid gasket curing, couldn't those drops wet the gasket, hindering the curing process? IMHO you should only apply a thin layer, for the sake of prudence (but I'm NOT an experienced mechanic).

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nath125

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Ahhh ok.  they are semi slick as they were removed (a month ago - so probably not that slick lol) but I take it they need to be soaking to move?

The worst thing is I just bought a wr400 5th and pinion for £10 that is coming next week so maybe I should leave it anyway.....

I wanted 3-5 but a tenner for 5th!  I couldnt resist.  Ive read that it you can have it yz 1-4 and wr 5th only.  Im not using it for motox, just pottering and the occasional long straight so it would probably help me right?

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nath125

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I'll give them a good oil but I don't think it will help :(  There is absolutely no movement at the mo

they are all aligned and in place with all parts inside/joining each other but better to try again. Bummer. 

Took me ages to get them in place!

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nath125

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Righty. So I managed to install the transmission correctly after I managed to grow an extra hand lol. 

This is something to remember for next time as it never shifted till the cases were together. 

 

I do have a more more pressing problem now. I noticed the crank "rubbed" somewhere when rotating, most likely when the rod was at the bottom of the rotation. 

I decided to put the cases together as the bearings were seated correctly and the crank looked ok and I thought that once everything was in place it may settle out (like the transmission) but it hasn't. Is this a normal thing until it settles out?

I'll put this in another thread to see if anyone can help (again)!

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YZDOC

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7 hours ago, nath125 said:

Righty. So I managed to install the transmission correctly after I managed to grow an extra hand lol. 

This is something to remember for next time as it never shifted till the cases were together. 

 

I do have a more more pressing problem now. I noticed the crank "rubbed" somewhere when rotating, most likely when the rod was at the bottom of the rotation. 

I decided to put the cases together as the bearings were seated correctly and the crank looked ok and I thought that once everything was in place it may settle out (like the transmission) but it hasn't. Is this a normal thing until it settles out?

I'll put this in another thread to see if anyone can help (again)!

Rubbing side or center?

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nath125

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50 minutes ago, Gary YZDOC said:

Very odd it would hit the case at bottom. Can you tell if the rod is hitting the case or the crank itself? 

I was unsure so I have opened her up again! 

The crank spins fine sat in right (clutch) side. I was looking at the main bearing on the left side and it looked that it was not flush with the case. I checked the manual and it says it should be so I heated it up and knocked it out to see if there was any debris that I may have not seen. 

It was clean inside and im pretty sure I seated it properly when I installed it but what they hey because I am paranoid I am getting another main and I will do it again! 

I also found out that my shift cam bearing was a little notchy so I will get that sorted as well. Time to buy a blind bearing puller!

As soon as the bearings come I will get them in and update the thread.  

If it still rubs after that then perhaps the shop didn't true the crank after installing the new rod?

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YZDOC

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47 minutes ago, nath125 said:

I was unsure so I have opened her up again! 

The crank spins fine sat in right (clutch) side. I was looking at the main bearing on the left side and it looked that it was not flush with the case. I checked the manual and it says it should be so I heated it up and knocked it out to see if there was any debris that I may have not seen. 

It was clean inside and im pretty sure I seated it properly when I installed it but what they hey because I am paranoid I am getting another main and I will do it again! 

I also found out that my shift cam bearing was a little notchy so I will get that sorted as well. Time to buy a blind bearing puller!

As soon as the bearings come I will get them in and update the thread.  

If it still rubs after that then perhaps the shop didn't true the crank after installing the new rod?

Could be it.

 

As far as having the blind bearing puller. Check the paper towel or pipe dope method before you buy a kit. 

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