Blowing Exhaust - Front Pipe (07 250 TXT Pro)

[miner]

As above.... asked the bike shop to look at my exhaust... this must’ve slipped their mind unless they didn’t want the hassle of spares/snapping studs. Asked them to look at the front pipe as it’s got soot build up and sometimes I think it sounds puttery up front, other times I wonder if that’s just how it sounds. They’ve obviously only pulled the mid and rear pipes though. 

I’ve not pulled it (scared of snapping the studs in the head - experience warns me this is likely!) and also that I don’t have any soft spares (gaskets/o-rings).... not tried cleaning it up yet either but will.... just wanted to get your experience on this. 

- Do the pipes go rotten? Or is it just a leak at the seal?

- What is the seal? Viton or copper o-ring? Or other?

- Success rate on the studs coming out without snapping?

Let me know about the above... pics below for info. Cheers. 

 

Edited December 11, 2017 by miner
Autocorrect

[lineaway]

Looks like rust, not any exhaust leak.

[miner]

On the KTMs the Viton rings go and they start blowing.... not sure of the seal on these. Top of the pipe looks more like soot, that’s what I noticed first. The corrosion came later. 

[d2w]

I second the simple rust theory. And note how the lower rad guard nuts are rusty and/or covered in what might be mineral deposits. Any chance your rad is leaking and dripping on the exhaust spigot?

[zippy]

Looks like rust to me,

I believe the Exhaust gasket at the cylinder is a soft metal "crush" type gasket.

Most likely the problem you will have getting the exhaust bolts out will be stripping/almost stripping the heads not breaking them.

[miner]

Bike isn't using any coolant but that's a good point worth checking... I think the rust has come from playing on the scrubland behind where we live, its salty and marshy and I've probably missed that as it lay dirty for a couple of weeks after I broke my hand.  I didn't realise how bad it was till I had to clean the bike and the Mrs quad bike.

So taking the rust aside... there's no history of these blowing the exhaust seal and soot collecting on inside of the pipe from the exhaust gas leaking at the flange/pipe joint? 

Taking the bolts out the head is like Russian Roulette.... its happened to me before but luckily during a top end rebuild (exhaust flange on my old KTM 200 EXC).  Anyone snapped them themselves on the GG?

 

 

 

[d2w]

I still see rust and possibly baked-on dirt/mud. I would have expected to see soot/blackness/oily residue around a leak, but I don't see that in your picture. Yes, if it's not broken don't fix it!  Those rusted flange nuts with what appears to be a hex-key head would be easy to round-out. But in that event you could always grind them off and then replace them with something more suitable.Soak the area with a penetrating oil first and lightly tap the head to break any rust joins.

Any chance there's a leak and what you hear is air being sucked into the pipe? Consider simply running a bead of high-temperature silicone/RTV around the flange/pipe junction and see if anything changes noise/cleanliness wise.

[miner]

Sounds like a plan.... my tyres wont make it in time for the track this weekend so I'll have all weekend to clean it up and check.... on the plus side my new trials helmet is coming with the tyres, every cloud!  Cheers guys, I will check it over properly at the weekend but as for cracking those bolts.... no chance!

 

 

[miner]

On 12/12/2017 at 6:46 PM, d2w said:

Any chance there's a leak and what you hear is air being sucked into the pipe? Consider simply running a bead of high-temperature silicone/RTV around the flange/pipe junction and see if anything changes noise/cleanliness wise.

Did that with the old 200 EXC... worked a treat, still got some there as well.

[miner]

Cleaned up a bit actually.... was in about with with degreaser First then rust remover. Not had a chance to fire it up and check for blowing properly because of work! But going to order some bolts and gaskets just in case as I need to order a new fuel cock. 

[d2w]

Actually, I had a more careful look at the exhaust of my 2008 TXT 300, and I realize that the pipe "header" is welded to the "parallelogram" flange which contains the holes through which the hex-head bolts secure the assembly to the cylinder/spigot. Phew. I suspect there's a gasket between the flange and the cylinder. I believe the gasket is a deformable/soft metal. So if there's a leak it would be between the flange and the cylinder and not in any area in your photo which is rusty. Perhaps the assembly process/weld simply made the join area more susceptible to rusting? And I don't see any signs of exhaust "leak" on the cylinder.

[miner]

Aye.... welding areas are corrosion hotspots due to various mechanical, metallurgical and electrochemical reasons.... google it if you’re bored. I spend all day explaining them at work, I’m out. ?