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Author Topic: YZ50 engine rebuild - PROBLEM  (Read 11251 times)

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Offline Hoony

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Re: YZ50 engine rebuild - PROBLEM
« Reply #30 on: September 12, 2010, 02:52:41 PM »
i can see the problem in the first pic, typical Yamaha basket woven crankcase  :D



seriously, it wont be a problem of pushed on too far as this cannot happen due to the shoulders, it will be its not pushed on far enough, more likely
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Offline YZ250H

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Re: YZ50 engine rebuild - PROBLEM
« Reply #31 on: September 12, 2010, 03:19:35 PM »
Yes, all these dramas I seem to have all the time (through lack of knowledge) have driven me to basket weaving in my spare time  ;D ;D ;D ;D
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"My inability to use emoticins in the right context is really getting me down :)
Quote from: GMC on May 03, 2014, 10:35:22 AM
The only triple jumps he would have been doing are the hop, skip & jump.

Offline vandy010

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Re: YZ50 engine rebuild - PROBLEM
« Reply #32 on: September 12, 2010, 04:05:16 PM »
the wear marks at "A" are small while the wear marks at "B" are more noticable.
i'd be wanting to check the crank for balance to see if it's running parrallel with itself. looks like it's got a case of the wobbles.
a balance check will answer that  easy enough. if it's in balance, then we move onto another idea. if it's out of balance, could be problem solved.
did you by chance drop the crank at any stage? was it stored in a box for sometime with a possibility of being knocked?
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Offline wmc83

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Re: YZ50 engine rebuild - PROBLEM
« Reply #33 on: September 12, 2010, 05:15:44 PM »
I know it's been said before but is the bearing the correct width? Maybe yamaha over machined the bearing retainer in the case did you try tapping the crank to bring it back off the case? (unlikely I know just a thought)
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Offline YZ250H

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Re: YZ50 engine rebuild - PROBLEM
« Reply #34 on: September 12, 2010, 05:20:41 PM »
Yeah. I did give it a heap of good wacks from both sides to no avail.  I think I will press the crank out of the RH case and do some measuring.  I didn't fully measure it up before I put it back in - just made sure the big end was sound.  Probably my downfall at the end of the day  :-\.

If one of the halves is a bit out of wack (just a bit) maybe it would have that effect.  Maybe it's not the bearing getting tight at all but the crank rubbing on the case 'cause it's out of wack.  Who knows - I don't  ::)
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Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
Quote from: GMC on May 03, 2014, 10:35:22 AM
The only triple jumps he would have been doing are the hop, skip & jump.

oldfart

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Re: YZ50 engine rebuild - PROBLEM
« Reply #35 on: September 12, 2010, 05:26:18 PM »
While you are at this stage ...what is measurement of crank webs left to right, is the crank pin flush with webs.
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Offline YZ250H

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Re: YZ50 engine rebuild - PROBLEM
« Reply #36 on: September 12, 2010, 05:42:24 PM »
The crank pin is a little bit proud on the LHS.  Can't see the other side obviously.
I will do some meaurements.  I assume you want a few measurements all the way around.

Edit - probably almost a mm difference between smallest and largest dimension.  I'm only doing it with vernier calipers.

Seems like my crank needs some work yes ??  I've got another one - I'll have a look at it
« Last Edit: September 12, 2010, 05:49:52 PM by YZ250H »
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Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
Quote from: GMC on May 03, 2014, 10:35:22 AM
The only triple jumps he would have been doing are the hop, skip & jump.

monaro308

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Re: YZ50 engine rebuild - PROBLEM
« Reply #37 on: September 12, 2010, 08:15:54 PM »
Is there a gasket in between the cases or just 3bond,hard to tell in the pics.
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Offline Billet YZ

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Re: YZ50 engine rebuild - PROBLEM
« Reply #38 on: September 12, 2010, 08:22:58 PM »
Quote from: Hoony on September 12, 2010, 02:52:41 PM
i can see the problem in the first pic, typical Yamaha basket woven crankcase  :D



seriously, it wont be a problem of pushed on too far as this cannot happen due to the shoulders, it will be its not pushed on far enough, more likely

Hoony,
          no disrespect but you need to stay away from this topic as i think what is confusing you is a set of crankcases that haven`t got a big hole in them.  ;D ;D

(Shit i`m gonna regret being a smartarse when Hoony catches up with me.)

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Offline YZ250H

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Re: YZ50 engine rebuild - PROBLEM
« Reply #39 on: September 13, 2010, 09:40:43 AM »
Quote from: monaro308 on September 12, 2010, 08:15:54 PM
Is there a gasket in between the cases or just 3bond,hard to tell in the pics.

Just threebond.
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Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
Quote from: GMC on May 03, 2014, 10:35:22 AM
The only triple jumps he would have been doing are the hop, skip & jump.

Offline whitey 43

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Re: YZ50 engine rebuild - PROBLEM
« Reply #40 on: September 13, 2010, 04:38:54 PM »
Just another tip...When you sort the crank out & ready to put back together, warm the cases in the oven (my wife loves it!) & take the bearings out of the box & put em in the freezer-it shrinks them a tiny bit. When you take the bearings out of the freezer, make sure you grab them in the middle (stick your fingers in the hole) & they will just fall straight in,no hammering or force at all. You can do the same with the crank too.Hope this helps, worked heaps of times for me...
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Offline YZ250H

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Re: YZ50 engine rebuild - PROBLEM
« Reply #41 on: September 13, 2010, 05:38:15 PM »
Thanks for that Whitey.  I am working on making one of those crank installer tools as well.
Strangely the bolt holes for the case splitter are a different dimension on the RH case than the LH.  Have to modify my case splitter as well now.  All these things take time.

I might take the crank to the shop to get aligned etc.  If they have to take it apart I will get a new big end.
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Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
Quote from: GMC on May 03, 2014, 10:35:22 AM
The only triple jumps he would have been doing are the hop, skip & jump.

Offline whitey 43

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Re: YZ50 engine rebuild - PROBLEM
« Reply #42 on: September 13, 2010, 05:46:20 PM »
Hope it goes well 4 u
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Offline Hoony

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Re: YZ50 engine rebuild - PROBLEM
« Reply #43 on: September 13, 2010, 10:09:30 PM »
Quote from: Billet YZ on September 12, 2010, 08:22:58 PM
Hoony,
          no disrespect but you need to stay away from this topic as i think what is confusing you is a set of crankcases that haven`t got a big hole in them.  ;D ;D

(Shit i`m gonna regret being a smartarse when Hoony catches up with me.)


Hey Pete, i'm never going to be allowed to forget that one am i  :D  and with the amount of riding you do lately i doubt i will ever catch you mate  ;)
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Long time Honda Fan, but all bike nut in general, Big Bore 2 stroke fan.    http://www.youtube.com/watch?v=XJoKP6MawYI
1985 Honda CR500RF "Big Red"
1986 Honda CR250RG
2005 KTM 300EXC "The GruntMeister" ( I love that engine)

Offline Billet YZ

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Re: YZ50 engine rebuild - PROBLEM
« Reply #44 on: September 13, 2010, 10:11:52 PM »
Quote from: Hoony on September 13, 2010, 10:09:30 PM
Quote from: Billet YZ on September 12, 2010, 08:22:58 PM
Hoony,
          no disrespect but you need to stay away from this topic as i think what is confusing you is a set of crankcases that haven`t got a big hole in them.  ;D ;D

(Shit i`m gonna regret being a smartarse when Hoony catches up with me.)


Hey Pete, i'm never going to be allowed to forget that one am i  :D  and with the amount of riding you do lately i doubt i will ever catch you mate  ;)

It`s all good Hoony.
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