Exhaust problem: Your 2 cents

[Drummert]

Long story short: There was smoke coming from between cylinder 4 and the exhaust header on my GS750E. I hoped for it to be just the gasket, but apparently it's a bit more than that.

Now the question rises what to do:

1. Saw a bit of the start and end of the pipe. -- Is this even possible without much problems? Is the pipe still straight enough to connect? Just as a temporary measure ofcourse.
2. Get a new exhaust header -- Will cost around 100 bucks if my searching was allright, still if the other headers are in the same shape (look to be in the same shape on the outside), 3 seems a better solution:
3. Get a new exhaust system --If the other headers are in the same shape (I don't know yet) it might become cheaper than doing all parts of the exhaust one at a time. Especially because the mufflers themselves aren't in the best condition anymore either. Problem here is a lack of money at this time, so option 1 (if possible) would be a temporary fix.


This is what I got to see when the clamp was out of the way:



And yes, one of the bolts broke of... Jeej...

[Grimly]

Looks as if that's the original twin-walled header. You could get it filled up with weld (or braze) for an extra year or two, but it will probably start falling apart in other bits. That's a lot of wear and tear, so the rest of the system will be similarly worn out and thin in parts.

[Drummert]

So, basically, my safest bet would be a new exhaust system then? Does twin walled mean twin walled on the engine side or the exhaust side?

[Grimly]

The downpipes were twin-walled simply to keep the shiny chrome intact and avoid the blueing that so many find objectionable (to me, blueing is nothing odd or unusual, a bit of blueing is normal and is actually useful as an indicator of overheating) Anyway, the posers won the day and we were saddled with twin-walled pipes from the exhaust port to the collector box. Replacements usually aren't twin-walled, but if stainless will last a while anyway, and can be shined back up again once discoloured by road muck. Stainless is not indestructible though; my own set of Motad stainless pipes and muffler is approaching the end of its life, but it took 25 years and a LOT of miles to get there. I'd have had several sets of mild steel pipes on it in place of that one system by now.

[Drummert]

Ok, so if I understand it right, the black pipe I can see between the rusted part still in the head and the rusted end of the pipe would be the inner pipe of the downpipe? I already ordered a new gasket last week, so I can try and take the exhaust of and get a new gasket in there and reconnect the inner pipe.

I was thinking of getting a new exhaust system in the end, so I will go and look for a stainless steel one. For the time being I'm thinking of wrapping the exhaust to keep it from rusting further. Would it be possible to reconnect the inner pipe for now and leave the outer pipe as it is? Problem is, I don't have the ability to weld/get braze in there.

[Grimly]

You could try bodging some exhaust paste into the corroded gap, but it won't last very long, if at all.
If it lasts a week, you could just keep on re-doing it, but it will become a pain in the ass eventually.
There's only one real solution - well two, in fact; get a good used system or splash out on a Delkovic.
There are lots of good used downpipes around and if there's a breaker near you it's easy to inspect them for solidity.

[Drummert]

Well, I removed the complete exhaust system today. Lucky that I did:

All the other bolts went out after some heating with a creme-brulee burner (hey, it works!) and I was able to take the pipes of. On the left side of the bike, I gave a little pull on the exhaust as a sort of joke, but instead the exhaust fell of. Turns out that the mounting bracket on the back end was completely rusted through... I guess I'm lucky I didn't find out about that whilst riding.

I decided to go the more expensive but better way and start looking for a complete new exhaust system. I was looking at those MACs, but I want to stay with the 4-2 design and I don't like the turnouts they have. The straight ones appear to be only for 2nd gen 750s. I did find some over here:

http://en.marving.com/gs-750-1977/accessories/couple-of-homologated-end-mufflers-marvi-line-chromium-plated-495.html

If I go for those, I will still need to find some downpipes. I couldn't find the Delkevics for a first gen 750, but an email could probably solve that i guess?
A little search on ebay gave me some results for used downpipes, but a lot of them look rather beaten up.

[Drummert]

Got a response from a local muffler shop, saying they can make me some pipes for 1100 euros, not sure about that one yet.

What do you guys think of a marving 4 in 2? I will have to let someone make some downpipes or get some I can fit on there in that case.