Downpipe fused to engine

[Sigals]

I recently bought a 2010 CBR 125 and as I was riding it a few days ago the exhaust snapped off as it was extremely rusted.

The problem is that it snapped just where the down pipe enters the engine and it seems to be so rusted that its fused to the engine.

I'm having a lot of trouble getting this part off - I've tried soaking it in WD40 for a few days but that's not made any difference.

I took a dremel to the outside of it trying to release the rust seal but haven't had much luck there.

I've seen a few other people with the same issue where they used a blowtorch or blowlamp to heat it up but I'm concerned about warping the aluminium engine.

You can see the problem here: https://i.imgur.com/8g2xGuE.jpg

I'm pretty much lost as to where to go next.

Any advice would be appreciated.

[Copycat73]

I`ve seen this happen once before .. on an XT500 .. using a cold chisel tool & a hammer he knocked the stump via the jagged end in circular movement and spun it out of the exhaust socket hole .... there looks to be plenty of metal there to get the chisel into..
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Whatever I post I have no citation and no intention of providing one..
caveat emptor

[Pete.]

Get a large cold chisel and put the end of it flat on the side of the exhaust collar where the line is in the pic attached. Take a medium sized hammer and give the chisel a few stout clouts. Hopefully this will cave in the side of the collar and break the rust bond.

You have to be brave and hit it with confidence, and you have to have the chisel square against the collar, not cutting in at an angle.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stinkwheel]

Being honest. If it were mine, first thing I'd try is a crowbar/giant old screwdriver with bent tip (I presume everyone has one of these) in the hole and start trying to lever it out. If you can get the end hooked under the rim of the steel where the gasket goes and start it rocking even slightly, you can then work penetrating oil into the gap that appears and keep working round until it comes.

Risk of snapping the casting if you're overly forceful doing this.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Rogerborg]

CBR125s are always doing this. First, forget WD-40, get some PlusGas in there.

What Pete said, although I'd dremel along that line first then try and fold it in.

You may find that the bond is stronger than the remains of the exhaust and you just end up knocking lumps off the exposed part without shifting the portion stuck in the engine. In extremis you might have to take the head off to get enough access - I had to do that on a Hyosung 125 with the same problem.

Best of luck.
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[dydey90]

Been there. Much blood. Many sweat. Such tears.

Took so much to get out that I kept the stump as a souvenir.

I ended up dropping the engine out, getting it in a vice, stuffing it with a rag and cutting a slot in the stump with a hacksaw blade.

These days I'm much better welder though, so I'd probably try welding a stick on and either turn/wiggle* it out or find something to jack it against.
I appreciate that welding gear isn't readily available to most people, however.

*sorry for using the technical terminology.
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This post is probably not serious and shouldn't be taken literally.
Past: CBR125,ER6f NINJA 650, ZZR600 Current: VFR750

[stinkwheel]

[Pete.]

You could easily burn it out with a stick welder. Stuff a soaking wet rag into the port use a thin rod and turn the amps up. you'll melt away the steel tube but not bother the ally at all unless you were very clumsy.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Copycat73]

given the difference in meltin point of mild steel and aluminium alloy do you really think this is such a good idea .. ???
____________________
Whatever I post I have no citation and no intention of providing one..
caveat emptor

[Pete.]

Yep it's a great idea. Aluminium has far superior conductivity. It might melt at much lower tempt but it conducts heat away so fast it takes a lot longer for it to get there locally that the steel will burn away before the ally gets to melting point.

That's why your piston doesn't melt at combustion temperatures
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Copycat73]

[Pete.]

Bad analogy. Combustion temperatures are constantly 900 degrees yet the piston doesn't melt, not at all like a one-off hit with a welder.

The guys at work build up concrete cruncher jaw seats by g-clamping a pair of ally plates across the sides and filling the gap it with 1.2mm wire. Typically they'll fill a gap 20mm wide by up to 40mm deep building the weld up directly against the ally. The plates don't melt despite being blasted with a 3 phase mig on spray transfer for extended time because the heat is conducted away too quickly.

Aside from that aluminium instantly forms an oxide layer that resists 3x ally melting temps. Since you've done tig you should know that because it's the reason you have to tig ally on AC current - to break away the oxide layer.

I'm not saying you couldn't fuck it up by arcing directly against the ally, but it would be easier not to.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Copycat73]

all the external oxide will do is act like a bag stopping the aluminium from spillin to the ground.. it won`t stop it deformin.. take a look at those plates and you will find they are marked and not the "flat" surface they started with..

I`ve yet to see a modern welder machine that don`t use AC.. MIG. TIG. or MMA.

can you give an example ?
____________________
Whatever I post I have no citation and no intention of providing one..
caveat emptor

[Pete.]

No I don't have to. I've done similar - it works. Simple as that. Time-honoured method of removing broken bolts and studs and you never hear of anyone burning away the ally there.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Copycat73]

OK ... .... well then .. just a thought .. are you gonna fix OP`s engine for him ?

would be helpful if Sigals provided a location ?

anywhere near Gateshead
____________________
Whatever I post I have no citation and no intention of providing one..
caveat emptor

[Pete.]

If I knew he was nearby, I probably would have already not only removed the stuck bit but turned up and welded on a replacement.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Sigals]

[Sigals]

Got an update to this.

Had a friend come round who's a mechanical engineer and he had a really long chisel so could get a lot of leverage and he knew exactly where to place it on the stump.

Ended up knocking it out with one blow - you can see the remains here: https://i.imgur.com/WtuocxT.jpg

I've got a new exhaust installed and working all good now!

[Pete.]