1986 XC400 Swingarm question

Looks like I am going to need a new swingarm for the 86 XC400. I've seen some on Ebay from a WR250 and they look the same, just wondering if anyone knows off top of their head it they are interchangeable.

Also ... how safe is it to weld any cracks in the swing arm? I've never experienced a cracked swingarm before so just a little curious.

86 XC 400 Swingarm.

Not sure if the previous owners did a massive cliff jump or was just something that happened over time. Seen a couple of Swingarms on Ebay but a couple either had welds, or cracks.

haha! Too late! I already had to easyout a frozen/broken bolt, then drill and tap it again! I will be sure to grease it up good.

plan is to get someone professional to weld it up. I pointed out a crack on one on Ebay to the seller, he thanked me and took the item off auction lol.

Ditto the chain / axle adjuster bolts. Both my 87 430 and 88 430 swing arms had frozen bolts from POs not doing maintenance. Only way to fix was at a machine shop. And one 430 was from SoCal desert.

Also, I believe the 86 400 was the first bike to get an upgraded - stronger swing arm... basically an 87 model year swing arm. There were suspension upgrades between those 86 -87-88 years

Hey all, Steve's brother here...
In my opinion, I think the mono shock mount cracks are from extension too fast too many times... there's a cap (stop or strength, not sure) welded on, and I think the mono shock linkage was hitting it. That's the only thing that visually makes sense...
I am taking it to get welded in 4 hours, hoping to be riding this weekend....

OK so now that I posted it, it's not making sense anymore....
Jumping it off a cliff makes more sense...

I would check the linkage bearings and shock too. Maybe the bearings are worn / bound, putting pressure on the swing arm. Is the shock absorbing hits well, does it need service too? Just saying... if the swing arm has been hammered that hard, all the other bits are probably affected too since they all operate together...

i agree with all of the above thoughts..never have seen the linkage area crack..something was bound in the linkage or shock i bet..
the swinger pivot tho, happens alot and is from bearing friction as in seizing and lack of grease. if its vee'd out and tig welded it will hold up well. it helps to leave the old bearing in while the repair is made to keep it round..just make sure the swinger gets pulled every season and greased and i dont think they crack then.

Got the swing arm pivot welded real well, but the shock pivot was being a pain...
Something in the paint ? Not sure... took it to a garage welder and he didn't have anything small enough to grind the shock mounts all the way. However, he was able to weld the first 1/2 inch, so I think it'll be OK for now, since both me and my brother aren't racing and jumping. The chain side bearing was bone dry, definitely need a new set....
That was the weirdest thing I've ever seen, where there was paint the tig wouldn't even melt the swingarm metal... bare aluminum worked beautifully!!!
Well, enough typing, time to wrench...

Also when I started wrenching on this bike, the suspension was set pretty weak, I think the previous owner jumped a lot with a suspension that repeatedly bottomed out. The shock pivot bearings were all greased, not the best condition, but at least it had grease inside... replaced a broken grease nipple (ha ha I said nipple...) everything will get injected with some red Lucas during assembly. Then I'll kick it over in the garage and inhale the sweet 2 stroke aroma until I can take it out and ride...

Can zero fittings be installed? In all the bearings on the swing arm? If there is room a small square block can be welded the drilled and tapped for a zero fitting.

there is zero room for a zerk fitting, unless the swinger bolt was gun drilled. the bolt is pretty tiny in these tho. the first italian huskies were gun drilled with zerks on both ends, but their pivot bolt was a bit beafier

They make a drive in zerk fitting
no threaded holes.

bring it to someone who welds aluminum for a living. they will know the correct prep and process.

It can be welded. You need a TIG WELDER.
I hope to set my shop back up someday.

Welll of course you will not get a good TIG weld thru paint. The repair needs to be clean all around the weld and cracks to be welded even cleaner. You can clean pre weld with contact cleaner.

welding doesnt work very well if paint and other contaminates are present. im doubting the welders skill if he was attempting it.