Advice: Dirt bike Frame Welds
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  1. #1
    Join Date
    Aug 2018
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    12

    Advice: Dirt bike Frame Welds

    Hi

    My son and my winter project is to put together a 1990 Suzuki RM125 dirt bike.

    I’ve disassembled it and had the frame sandblasted.

    I’m not sure what to make of the welds. Aesthetically they look terrible.

    A few examples before the sandblasting.





    Are they like this for strength? Speed of welding?

    Should I be grinding them flush?

    Thanks


    Sent from my iPhone using Tapatalk

  2. #2
    Join Date
    Oct 2014
    Posts
    575

    Re: Advice: Dirt bike Frame Welds

    The newest 2019 off road stuff from any manufacturer seems to have the same crappy looking welds just like those.

    Leave them alone and try to forget how ugly they are.

  3. #3
    Join Date
    Oct 2015
    Posts
    2,346

    Re: Advice: Dirt bike Frame Welds

    I have had many dirt bikes and street bikes. Your welds look like most all of the welds on the bikes I have had. Do not be deceived by the stacked dime look that you see on race cars all the time. The stack dime look makes them no stronger. These bikes are mass produced and the way the welds look is secondary. The hand made race car frames and such are hand made and the way it looks helps sell them so thats what they do.

  4. #4
    Join Date
    Aug 2018
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    12

    Re: Advice: Dirt bike Frame Welds

    Thanks for the info I guess I’ll leave the welds as is.

    I forgot to ask what’s the best way to fix this? Weld on a washer?



    Thanks


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  5. #5
    Join Date
    Jan 2019
    Location
    Tucson Arizona
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    119

    Re: Advice: Dirt bike Frame Welds

    Quote Originally Posted by acolic View Post
    Thanks for the info I guess I’ll leave the welds as is.

    I forgot to ask what’s the best way to fix this? Weld on a washer?



    Thanks


    Sent from my iPhone using Tapatalk
    make a new one and weld it on, as far as the other welds.. they look just like the welds on my 88 Husqvarna WR 500 liquide cooled 2 stroke, I bought it new in 88 to race in Baja and its been everywhere from wet muddy logging trails in Oregon to the deserts of africa since and of course Baja many times I still race it in "Classic" series races for us old guys so we don't have to try to keep up with the kids on modern 4 strokes etc.. I restored it 2 years ago and found using TIG was much easier with the thin wall tube they made the frames out of, I had to fab up a new radiator mount as somewhere over the years I'd torn one of the 4 and had brazed a washer over it .... the new mount looked much better... I hot tanked it before rebuilding and magna fluxed all the welds (I ran it very hard back when I was racing) and found no cracks in any of them....

  6. #6
    Join Date
    Mar 2005
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    Under a Rock
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    4,821

    Re: Advice: Dirt bike Frame Welds

    Quote Originally Posted by monsoon-mech View Post
    make a new one and weld it on, ..
    I agree.

    You are worried about how the factory welds "look" .... then you are gonna weld on a flat washer to fix a mount????
    make up your mind...
    LOL!

    .


    that said, I'd prolly weld on a washer and spray bomb it red...... then hit the woods...
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    True Wisdom only comes from Pain.

  7. #7
    Join Date
    Apr 2012
    Location
    socal
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    511

    Re: Advice: Dirt bike Frame Welds

    Same guys that weld Harbour Freight stuff together, , , ,
    ' ' ' ' "Move along, move along, theres nothing to see here, , , ,"

  8. #8
    Join Date
    Feb 2012
    Location
    Sweden
    Posts
    676

    Re: Advice: Dirt bike Frame Welds

    If a weld has held up for 29 years on a motocross bike... it's probably good enough.

  9. #9
    Join Date
    Aug 2018
    Posts
    12

    Re: Advice: Dirt bike Frame Welds

    Quote Originally Posted by John T View Post
    I agree.

    You are worried about how the factory welds "look" .... then you are gonna weld on a flat washer to fix a mount????
    make up your mind...
    LOL!
    Ok you got me there.


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  10. #10
    Join Date
    Jul 2008
    Posts
    2,287

    Re: Advice: Dirt bike Frame Welds

    Quote Originally Posted by G-son View Post
    If a weld has held up for 29 years on a motocross bike... it's probably good enough.
    LOL, ya THINK???

  11. #11
    Join Date
    Dec 2010
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    SoCal-LA
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    9,290

    Re: Advice: Dirt bike Frame Welds

    Most likely that frame is 4130. A washer at the frame mount is a good idea but don't dwell in the weld zone for too long while welding. You don't need to have to use 4130 for the washer since you are not going to heat treat the weld. ER70 filler is just fine.
    Weld like a "WELDOR", not a wel-"DERR"
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  12. #12
    Join Date
    Jan 2004
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    Brethren, Mi
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    841

    Re: Advice: Dirt bike Frame Welds

    I have an OTC engine hoist, my bud has a HF one. Guess which has wayyyyyyyyyyyyyyyyy better welding?
    The welding on dirt bikes has never been much to look at. Its so thin though that a noodle is sufficient most of the time. A couple flat washers stacked is a good fix for that, wouldn't be the first time its been done.
    Part of the maint of those is continually tightening bolts. Farmer tight on the engine mounts.
    Last edited by Sberry; 10-18-2019 at 09:49 AM.

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