As the title states, I somehow managed to crack the frame on my 2008 yz125 that I’ve owned since it was practically new. I was hitting a lot of sandy whoops the last 2 days and think that is probably what did it. The crack was definitely not there 3 days ago when I had the gas tank off.
So I’m kind of wondering what my options are. I would prefer to have it welded because the title is in my name ( it technically can be ridden on the road if I ever decided to do this). I’m afraid of buying a used frame because I don’t know the history of it. It could crack right away again for all I know.
The hang up on having it welded is that I don’t think too many people know what alloy the frame is. I’m thinking a local shop would just guess the alloy and run a weld on it. I don’t want that. I want it welded properly if it does get welded.
I’m not a welder by any means, but to me it looks like the weld cracked in the middle of a bunch of porosity. I would appreciate any input (especially if someone has welded or had these welded before with success).
My amateur DIY guy self says that a competent welding shop should have no problem with that. However, I will leave myself open to being corrected by those that know better. There are some very knowledgable folks here. Paging Bearuno, Sandman, FGR01 and others to the white courtesy phone!
Appreciate the input. Like i said in the post, I’m not a welder in any way, shape or form. I’ve always heard that aluminum was difficult to weld.
I can't weld aluminum.. but I am pretty slick with the Vital search function! 😁
In this thread, you can see where DV12 had the same YZ issue and had it repaired:
https://www.vitalmx.com/forums/Moto-Related,20/Went-riding-on-the-smoker-today-Here-some-photos,1220609?page=3
Another thread about welding YZ frames:
https://www.vitalmx.com/forums/Moto-Related,20/15-16-Yamaha-frame-cracks,1294019?page=0
Wow, dv12’s is a little worse than mine. You think his held up ok after getting it welded?
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Not sure. It looks like a very good weld to me.
Allegedly these frames are a weldable 7000 series alloy.
I've done a subframe ear on a 2014 YZ450F main frame and it worked out well.
Grind a clean, straight V into the crack using a clean carbide burr (don't use abrasives, they can leave contamination behind).
TIG the crack with 5356 filler rod and 100% argon gas. Allow the weld to air cool.
Loose engine mount bolts or shock and suspension linkage bolts can cause frames to fail, so check all of that stuff.
In my opinion, a crack through a factory weld is fully repairable.
When a frame cracks through a main tube, through a major forging or casting, it will never be the same after a weld repair.
I appreciate the input. Actually, the only reason I discovered the crack in the first place was because I was running through and checking torque on all the major bolts of the bike (all the engine mounts, linkage, swingarm ect). I do that every other ride as part of routine maintenance. That’s how I know the crack only appeared within the last 4 to 7 hours of ride time. It caught my eye almost immediately.
Now if I May ask a couple more questions since I know nothing of welding
1. Should I drill holes at each end of the crack to prevent it from spreading?
2. Should the frame be heated before and during welding?
I mean DV12 is literally David Vuillemin himself so I would definitely hope so lol
Welding process and heat treating process depends on the aluminum alloy. I recommend reading up on the subject.
6061 alloy loses strength near the weld where the heat has degraded the material. After heat treatment, 6061 can be returned to nearly full strength.
7075 alloy is considered non weldable because it loses significant strength near and in the weld.
There are alloys like 7005 used in the bicycle industry that will age back to nearly full strength if welded, air cooled and allowed to age.
I have an account with a supplier who sells tubing to the bicycle industry. This is what they say about their 7005 tubing:
"Artificial age 7005 frames to T6 condition: age 6 hours at 200°F (+/-10°F) plus 4 hours at 320°F (+/-10°F). "
The key there is that it's an artificial aging process, or a way to speed up the aging process in the heat-affected zone around the weld.
The T6 heat treating process for 6061 aluminum is much more involved, requiring higher temperatures and a quenching step prior to an artificial aging process.
Allegedly, the Japanese aluminum frames are made from alloys in that weldable class of 7000 series aluminum.
They are very high strength, but they can be cold-welded in production without requiring significant post-weld heat treatment.
I am not a metallurgist and I doubt Yamaha will ever tell you what alloy their frames are made from.
The only way to know for sure would be to take a frame to someone with a X-Ray fluorescence analyzer to determine the chemical composition in the alloy. Large metal scrap outfits and metallurgy labs have that equipment.
I did some reasearch last night. I’m sure you already know this, but it does seem like 5356 filler rod covers the bases for a lot of 6xxx and 7xxx series aluminum. Not knowing the specific alloy shouldn’t be a problem (please correct me if I’m wrong).
I also found this which references a 2007 yz250f. It should have the same alloy make up as my 2008 yz.
There have been issues with a variety of YZF frames- at / along welds.
There's been quite a few threads on it all, here on this site, alone.
I'm stuck on a phone, and, don't know that intimately your frame, but I presume it's at the rear backbone / shock 'tower' area, and it being the weld attaching the Backbone Shock Tower to the hollowed out 'To The SA 'pivot member.
Find an experienced / expert welder, and, to make it cheaper for yourself - as, 'prep' is the Real Cost (Time, Is Money) in most repairs - grind out / down that weld. And, I'd advise, the weld on the other side - if one side has cracked, I'd say the other will too. Though, you may get away with just the one side - but I'd not just go that route.
Your mention of 'contamination' - that may or may not be the cause of the cracking - But, it Is a Big Thing to consider with your grinding down of the cracked weld - it's imperative that you remove whatever grit that your grinding Medium(s) can leave in the Aluminium. Final finishing of the 'grind' should be done by a Metal Burr / File / Whatever. No weld on Any material takes kindly to contamination, but Aluminium, as a common material / weldment, really doesn't do well with it.
While you are at it, Check All Parts of the frame for cracking. I've found, almost inevitably, that there will be cracking elsewhere - no material has an infinite life ( even the much fabled Titanium ) - Alumimium, certainly has it's problems with 'ageing out / stress cycles. when subjected to the incredible stresses we put our machines through. Your frame has served you / others well, over what could have been over 18 years of use.
Appreciate the response. You are correct about the area of the crack. It is up by the shock tower area of the frame.
It was suggested to me to find somebody who is certified in welding on aircraft. For obvious reasons, those guys are held to very high standards. I don’t really want to take it to just anyone who “knows how to weld aluminum “.
I do plan on doing the prep work for the welding. I was going to buy some carbide burrs and carbide drill bits for the prep. And use acetone to keep things clean during the process. Research shows that any tool that has been used on something else will cross contaminate the aluminum, so I’m just gonna get all new tools.
As for the frame itself. If I have time today, I’ll be looking it over. The bike has 7 years of use on it at the most. The previous owner (and original owner) was a vet play rider who had health complications immediately after buying the bike new. It sat in his garage for 12 years until I bought it. Under my ownership, it has seen a lot of single track riding. I do moto it occasionally, but most of its hours come from the woods.
When the crack appeared, I was riding terrain that I (nor the bike) have never ridden before( 1800 miles from home) A lot of 2 foot tall, high speed whoops, “gravity cavities” and stuff like that. Stuff that I’m sure could expose any weak points in the frame. It was probably the hardest I have ever punished a bike tbh.
My .02 on you prepping the frame to be welded, check with the shop that you choose to weld, most shops around here wouldn't put their name on something they didn't do from start to finish.
This is a solid piece of advice.
I do my own welding, hence the prep advice.
Show the crack to your welder and get their input before doing anything.
Agreed. The last thing I would wanna do it make it harder to weld for somebody. It’s kinda difficult finding someone who welds aluminum on a regular basis (atleast in my area). There are people who weld aluminum, but it’s more like non structural decorative stuff. I’d rather wait and find someone who is confident they can fix it right.
Maybe try finding a welding shop that builds aluminum framed mountain bikes.
Those guys are definitely into the higher performance structural stuff with the same alloy, or similar alloys.
I didn’t think of that one. Those guys would be pretty qualified too. Thanks for the suggestion.
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