How not to repair stripped threads

[MarkyMark]

Album with slightly better descriptions here: http://imgur.com/a/UOXLH



1989 Yamaha SR 250 oil filter cover, I'd stripped the threads for the bleeder screw, and this seemed like a good way of repairing that.

http://www.aluminumrepair.com/thread-repair.htm

-the guide I was using

https://www.youtube.com/watch?v=RCrixbXz4rc#t=60

-What I was hoping for

What on earth is that bubbling? I'm assuming the black shit is the oil I failed to clean off burnt onto the surface.

I wonder what sort of alloy this was in the first place, and what I've done to the heat treating. Was I supposed to do something different to avoid snapping my screw or was it just small/ weak/ unlucky?

Also, shit, I can see some of that bubbling both in the groove for the O-ring, and some very small ones on the mating surface. What's a cheap and easy way to smooth that out, is hand sanding safe?

There's a wrecker on Trademe I can get a new cover off for $20 plus shipping if this absolutely fails, but I don't want to put more money into the bike than I need to.

I really wish I'd gone for drilling and tapping for a larger screw now, but brazing seemed so nifty...



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[Akzle]

you? Brazing ally?
Do yourself a favour and fork out the 20.

Then practice brazing ally.
Get a fine ass tip and try and coat the inside of the hole, then normalise the whole piece, then drill n tap.

[Akzle]

oh! Now i see the pocket torch. Hah.

[MarkyMark]

Me? Shit, who here do I know in real life?

It's not the $20 (well, not only the $20), it's the principle of not admitting I've fucked it until I absolutely have to, and beaing able to repair rather than replace shit in general.

[Akzle]

it's by no means impossible. but for someone with maverage tooling and maverager skills, it's highly unlikely.

it's not a fuck up until it's in the bin.

pre heat piece, then area, then spot heat to braze. i hope you've got flux for your rod.

[The Pastor]

The ali soaks up oil, when you heat it, all the oil comes to surface. It will stuff up any type of brazing.

i like that HTS 2000 tho, looks cool. Wherd u get it from? and how much?

you could try to gently heat the area, and then wipe/sand off the black stuff and see if you can get it off? i'm not too sure on the best way to do it.

[neels]

Why did you not just helicoil it?

[Akzle]

you could try to gently heat the area, and then wipe/sand off the black stuff and see if you can get it off? i'm not too sure on the best way to do it.

"that black stuff" is likely soot, and should all but wipe off. ..

[The Reibz]

You should have just drilled it out and re tapped one size up, would have been much easier. Never mind this brazing and helicoil shit.
You can still salvage the casing, Sand all the oxides back with 80g, then 120g, 320g, 400, 800, 1200 and finally 2000 and polish. A mirror finish should be attained if you did it right.

Seems like alot of effort for a bleeder hole ay

[MarkyMark]

http://www.trademe.co.nz/business-farming-industry/industrial/manufacturing-metalwork/metal-supplies/auction-515062524.htm trademe store of this outfit: http://www.thetoyshop.co.nz/ They were selling 'em on trademe for $3 (per rod?) but had run dry before the next week's shipment when I was there and took pity on me by giving me a few offcut bits.

Apparently it works through oil and oxdiation and doesn't even need flux, which I found hard to believe until it tore my damn screw in half.

Helicoil I didn't have and it would have been cheaper to buy a whole new cover than tool up for that. In hindsight I should have drilled and tapped but wasn't sure if the copper (?) washer was anythhing special or whether I could find an appropriate larger replacement in my bolt collection.

The black stuff isn't soot from the flame, I could watch it appear and it's definitely come from the heat and the aluminium, not the flame. I figured cleaning it off the cosmetic side will just emphasize the ugly lumps, and the bike's no looker anyway.

I sanded the mating surface, and unfortunately didn't have many intermediate grades of paper so went straight from a faily coarse grit to a whetstone to Jif/ brasso on a pane of glass rubbing the shit out of it. At this stage I discovered the mating surface had warped a bit too, but luckily in a way that tightening the screws tended to counteract.

Got it up to a smooth and flat surface reasonably well, tightened the hell out of it, and now it just baaaaaarely leaks, tiny little 1/2cm dribble after 20 minutes of riding including plenty of high revs. I think the problem there is the small bubbles on the inside face of the o-ring groove meaning the o-ring can't seal it.

Two questions: What the hell are the bubbles? Water or oil pockets inside the ally that expanded in the heat? Google fails me.

Could I stop the rest of the leaking by just adding a gasket in here to supersede the o-ring? Apparently cardboard cereal boxes work a treat for gasket material...


If you saw the state of the rest of the bike you'd see why I'm so keen not to put money into it unnecessarily...

Edit: third question: as you may have worked out I'm just running with a permanently closed breather hole. I'm hoping this will send a few unhelpful burps of air through the system and then not matter. Am I missing anything I'm going to regret drastically?