Author Topic: Torn engine mount bracket on the YZA whats the best repair method  (Read 3374 times)

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Offline Freakshow

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Spew, Had just finished prepping the 360a for the Aussie titles and noticed the rear motor bolt had broken, went to replace it thinking it was from my accident only to realise the rear mount is out in one side by 2 mm enough to not line the edge of through bolt in.

Cutting the story short I went to front and noticed there is a crack around the front mount and its been pulling back and tearing the plate... Spewing. So have bit the bullet and pulled motor out to be sure and sure enough its through 50% of its area, if you drew a circle around the mount.  it appears to just be on the bracket mount not the tube but not sure how to tell, but assume I wont need to sup[port the tube.

So now given it appears to have torn on the bracket welded to down tube and I assume its not in the tube then so I can just tap it back and get it welded ?

So should that be welded as a strong weld or a flexible one like brasing ?

If they a mig will it imbrittle the mount and start a crack fest ? What's the go here people who know there welding and stress/ vibration stuff long term I don't want more problems.
pictures of the issue

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74 Yamaha YZ's - 75 Yamaha YZ's
74 Yamaha  flattracker's
70  Jawa 2 valve speedway's

For sale -  PRE 75 Yamaha MX stuff, frame, motors and parts also some YAM DT1,2,A and Suzi TS bikes and stuff

Offline topari

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #1 on: August 10, 2014, 03:03:15 pm »
Can you post pictures. Facebook is blocked at some sites, including mine.
topari

1979 IT400F, 1984 kdx200

Offline kdx Geoff

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #2 on: August 10, 2014, 03:06:50 pm »



 :)
Buying kdx air cooled drum brake unitrak bikes and parts

Offline yamaico

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #3 on: August 10, 2014, 07:03:18 pm »
Tap in back into place Freaky. Once you're sure that it's in the right spot and everything is lined up grind a vee in the crack with a die grinder to get decent penetration and then get someone competent to TIG weld it up. They will need to go past the end of the crack at either end, but a good welder will know that anyway. It's only on the engine mount support tube, so it will be fine. Whatever you do, don't get it brazed.
Pete.

Offline SlideRulz

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #4 on: August 10, 2014, 07:58:28 pm »
Yep, what Pete ( Yamaico ) said, but.
Why no to brazing Pete?

Offline yamaico

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #5 on: August 10, 2014, 08:56:49 pm »
In my experience Steve if it's a stressed joint the brazing will invariably crack. Trying to weld a joint that has been brazed is near impossible as the brass continually contaminates the weld.

Offline SlideRulz

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #6 on: August 10, 2014, 09:13:34 pm »
I knew there'd be a good explanation. :)

Offline Lozza

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #7 on: August 10, 2014, 10:33:35 pm »
Heat it up slowly with flood lights and a LPG torch , weld it (as per yamaico's method above ) , cool it slowly with the floodlights and wrapped in a fire blanket. Do the weld preferably in the middle of the day.
Jesus only loves two strokes

Offline shelpi

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #8 on: August 11, 2014, 10:09:12 am »
Tap in back into place Freaky. Once you're sure that it's in the right spot and everything is lined up grind a vee in the crack with a die grinder to get decent penetration and then get someone competent to TIG weld it up. They will need to go past the end of the crack at either end, but a good welder will know that anyway. It's only on the engine mount support tube, so it will be fine. Whatever you do, don't get it brazed.
Pete.
yep do that, and when doing the weld prep check for what gauge of metal is there as rust may have thinned the wall thickness, Marty is the best tigger that you will find , I can tig stainless, aluminium etc fairly well but I take my special stuff to him because he is that good  ;)

Offline shelpi

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Re: Torn engine mount bracket on the YZA whats the best repair method
« Reply #9 on: August 11, 2014, 10:22:55 am »


 :)
Hmm is it just the sacrificial web plate that cracked? have had to weld the frame tubes underneath as well a few times, to the point the chunk was gone and had to fabricate a new peice , was it loose engine bolts that caused this or ..... it costs nothing to check, go deaper 1st ;)