290 exhaust to cylinder, can't reinstall

[bron yr aur]

Buenas tardes a todos...

Just bought 2012 2.9, and have only ridden it 30 minutes. It's my first Sherco and only 2nd trials bike (2003 GG 280). I pulled the bike apart to clean it and check the jetting, bearings, etc. It is in very good shape. Piston is flawless looking through exhaust hole. 

 

Upon trying to reinstall the pipe into the cylinder, I realized it will not fit. It seems there's a metal gasket in the cylinder, and the pipe doesn't even begin to slide into it. It's as if the gasket shrunk while the pipe was out. Am I missing something? I had considered using the flange to gently "coax" it in with small turns on the bolts, but quickly envisioned a catastrophe, with stripped threads, or even worse. 

 

The gasket looks almost as if it has threads. Should I pry it out and lightly file it until the pipe fits? It's quite firmly planted in the cylinder, so again, I held off trying to pry on it for fear of the unknown. 

 

Any help would be much appreciated. I googled and YouTubed it, but nothing. Seems I'm the only one who 1) has this problem, or 2) is this daft. 

 

Thanks in advance. 

Edited October 11, 2017 by bron yr aur

[copemech]

Normally just get it started into the muffler then twist and push a bit to seat it in cylinder against the gasket. Set your flange and install screws and snug it up evenly.

[pauls320]

Its not uncommon for the header pipes to get bashed during its life, this can deform them slightly and mess up the alignment. Copemech is giving you Great advice, You can take this a step farther by removing the silicone o ring seals from the muffler flange and ''trial'' fit it to see how it fits up before final assembly...dont forget to reinstall the orings before final assembly.

[bron yr aur]

Yep, I tried everything to fit it, twisting, turning, sliding. It won't even start. Very odd. 

 

And re: O rings. Hmm there are no O rings. Are we talking about the same year? Or are they missing? I don't really see where they could go, except maybe the inner grooves on the gasket, the ones I mentioned in my OP that look like giant threads. But the bike did not leak at all, so I'm assuming they aren't to be installed on this year?

[pauls320]

Hi, there are supposed to be two in front flange of the muffler,there are grooves machined inside...maybe they are missing or just not visable (often gooped with sealant).. If your pipe has been bashed..you might have to wrap a rag around it and grip it gently in a bench vise and ''adjust'' it slightly with a rubber mallet, block of wood or something handy...?Maybe a piece of 2x4 as pry bar to open the bend ever so slightly...?? (the o rings should not be black rubber, should be red hi temp silicone type)   You can do it, after all its just a simple motorbike Do you have Sherco dealership close by you , that you can visit... 

[bultaco82]

Sounds like the gasket between the header pipe and the cylinder is what you are seeing. If so, pull it out and put it around the end of the header pipe and then install header pipe.The gasket should have some give to it.

[bron yr aur]

Awesome! The 2 last posts seem to be dead on right. 

 

That being said, the pipe is indeed quite abused, probably the only part of this bike that is. But the end going in the cylinder is obviously quite rigid and doesn't appear to have suffered any damage. Just for reference, I'm posting pics. 

 

Thanks so much to you guys all for taking the time. I just wanted to see if there were tricks to be used to avoid damaging anything... Which is what I got ?

 

[copemech]

Yes, a crush type sealing washer is used, however it appears you may have more than one installed, possibly to compensate for a bent header pipe and get it to seal, as I have done it myself one time.

Normally they look like this with only one gasket and a good pipe, it is inset a bit more.

I run a special oil that does not carbon foul, but that is top secret stuff!

 

[bron yr aur]

Yes you are correct. The previous owner had installed 2. I feel foolish. I didn't realize that the pipe fits up against the gasket and not inside it. So I've fit it up again. Now I'm just hopeful. I have a feeling it's going to leak since I didn't reinstall the gasket exactly as they were. Can they be annealed like the typical copper crush gaskets on some 2 strokes?

 

While we're talking, one more little bit of help, if I may ask. Where does this go? It fell out when pulling the tank and exhaust chamber off the back of the bike. It is basically the same rubber as an inner tube.  Thanks. 

 

 

[tony27]

It's not possible to anneal those gaskets, best thing to do is replace it if it leaks

The rubber piece you're holding is homemade, not sure where it fits but the slot may give you a clue

[bultaco82]

That rubber part looks like an extension to the rear mud flap used to keep the dirt off the shock. The hole would go over the ring  that the bottom of the stock mudflap slides into and hangs down to the swingarm to stop dirt and mud. Hope that helps.

[bron yr aur]

7 hours ago, bultaco82 said:

That rubber part looks like an extension to the rear mud flap used to keep the dirt off the shock. The hole would go over the ring  that the bottom of the stock mudflap slides into and hangs down to the swingarm to stop dirt and mud. Hope that helps.

You're a genius! Lol yep, that's exactly what it was. 

 

I'm going to attempt bending that pipe back the way it belongs. I was able to do some adjustment just with a rubber handle of a hammer between the bends and my hand strength. I should be able to do better with it in my vice. 

 

I'm also going to hunt some copper crush gaskets, like the ones on Kawasakis. They crush flatter, so I can couple the existing with the new and it will still allow the pipe to slide inside the exhaust port of the cylinder. If I ever have a moment of weakness and actually purchase a new pipe, I'll get the new Sherco gasket then.