1979 GS750 RC Exhaust head collars / spacers

[tobaccorancher]

Hi, I am putting my exhaust system back on and when putting it back on I am not happy with how it is going back together.

The PO put an RC Systems exhaust on, which I think is a good exhaust system. Each pipe had three collars? spacers? shown in photos, not sure of the exact nomenclature, photo links are below. There is a gap between these spacers around the exhaust pipe. I tried to see if four spacers would fit, but four will not. Plus, the spacers do not seem to fit very well inside the head as they make contact with the gaskets. They do not seem to conform well around the pipe.

I noticed some soot around the head when I took it apart, but did not think much about it. But, now I am thinking that the gaps in these collars are leaking at the gaps. I don't think the gaskets are strong enough to seal unless they have even pressure all the way around.

So, am hoping that the collective will shed some light on whether what I have is ok or what I am supposed to have to apply even pressure to the pipe flange and gasket.

20221211_184058 by Andy Hoover, on Flickr
20221211_184114 by Andy Hoover, on Flickr


Thanks!

Andy

[Grimly]

I had a similar exhaust on mine, and the ends of the pipes were flanged to allow the spacer ends to bear on them -only two spacers per pipe though, so less fiddly. One thing that happened was the manufacturing process was too hard on the pipe flanges and they all cracked eventually.
If your flanges are in good condition, along with new exhaust gaskets, your arrangement should seal, but I'd also be inclined to use some Firegum * at the meeting point, as a belt and braces setup.
*Firegum is what I can get, you must have a local equivalent. Basically a high-temp exhaust paste, usually grey in colour. I've found high-temp exhaust silicone, as sold for exhausts and stoves, is ok at the collector end of the pipes, but not really up to the job at the top (hotter) end.

[tobaccorancher]

Thanks, Grimly!

[tobaccorancher]

OK, continuing ahead, I tried to bolt up Forum cylinder today. When I removed these headers each pipe / cylinder had three collars / spacers between the exterior flange and the interior pipe flange. On cylinder 2 I noticed that when I bolted up the exterior flange one of the three collars was still loose. I wrestled with it a while, but could not get the exterior flange to make contact with it. So, I took it back apart and see that the exterior flange has a bow in it. I looked at all of the exterior flanges and see that they are all bowed. I'm not sure how I got Home cylinder to cinch up, just lucky I guess, but the bow on the others is big enough that the only way that I can get them to work is by using two collars / spacers and straddling them at each bolt.

So, is there a remedy for this? Is there a way to remove the exterior flanges to straighten them? Or are there better collars / spacers that I can use so that I can get even pressure on the pipe flange. After I took the header off I noticed a good bit of soot on a couple of the cylinders, so I don't think the pipe flanges were seated well before I took it apart.

Thanks,
Andy

[Grimly]

Other exhausts that I've no trouble with have a thickening sleeve welded on to the top 1.25" or so, so that the retaining collar is bearing on that, and the sleeve is pushing the whole pipe into solid contact with the gasket.
Might be something to consider.
If your collars are bowed, they've been over-tightened by the PO or somebody. If it's possible to dismantle the exhaust, you could simply reverse the collars so the bow is the other way around.
I take it you're not referring to the factory cast collars, as they'd be hard to bow, but the 1/4" sheet steel collars on aftermarket exhausts will bow quite easily when over-tightened.

[tobaccorancher]

Yes, these are the ~1/4 inch collars. I can remove the exhaust again pretty easily, how do I get those collars off? Will they slip over the flange at the end of the pipes?

[Grimly]

Yes, these are the ~1/4 inch collars. I can remove the exhaust again pretty easily, how do I get those collars off? Will they slip over the flange at the end of the pipes?

Depends on the design. Ideally, you could remove the downpipes from the collector and slip the collars off easily, but it all might be welded together at the collector.
Or...
The sleeves, being removed, might allow the collars to slip over the flange at the top end.