Need advice for Sachs exhaust leak

I have a 1980 Sachs Prima with a 505 D1 Engine. I am having an exhaust leak at the exhaust flange. If I spray carb cleaner on the connection, the engine either stalls or revs up very fast. I had the exhaust pipe clamped real secure to the flange and then held up with springs attached to the head fins. Without the springs the flange drops down 1 mm. The bottom of the flange is pitted and can’t possibly seat properly. Has anyone put a copper sleeve around the exhaust flange and shoved it up to seal the gap? It may better than Permatex 81878 Ultra Copper Gasket Maker. I would appreciate any other suggestions for sealing the gap.


Re: Need advice for Sachs exhaust leak

maybe strip up an aluminum can and wedge it in there.

Re: Need advice for Sachs exhaust leak

♣Slew Foot♣ /

The sax 505 has what they call a back Scavenging system that is why it leaks like that and it's also why if you put a bolt too far into the decomp and block it off completely including the internal passage the bike won't run right just so you know

Re: Need advice for Sachs exhaust leak

Thank you for the information. My decomp is working and does not leak. When I found I had a leak at the flange, I tried putting a compression spring between the head and the clamp which held the flange down. This kept the tailpipe from bouncing but increased the leak to the point it would not idle low. So, it seems I need the springs to hold it up. This might be necessary to compensate for the wear. If it runs ok that way, and I detect some leaking with the carb cleaner at the flange I should not be concerned?

Re: Need advice for Sachs exhaust leak

I always use springs to hold sachs pipes up. I've had plenty which got all loose on the exhaust flange and it's never been an issue. If I thought it mattered, and in your case it sounds like maybe it is, I'd just jam some strips of aluminum can in there to shim it tighter maybe. There's really no fixing those flanges.

Re: Need advice for Sachs exhaust leak

if u got skiilllz maybe u can braze it. im picturing the steel flange part red hot and that golden yellow braze goodness filling that gap. or maybe the dumb aluminum will repell it, dam.

Re: Need advice for Sachs exhaust leak

Thank you. I really appreciate the responses. I am going to reinstall the springs to hold the pipe up. It really ran fine that way. I was just checking for vacuum leaks and discovered a change of speed.

The real problem occured when I replaced the extension springs with a compression spring forcing the flange down. I was trying to fix a problem that I did not have and caused one.

Re: Need advice for Sachs exhaust leak

ive got an extra D cyl with a loose exhaust flange i just swapped out

you can have it if you wanna fuck around with brazing before wrecking yours

its ugly and pretty sure the decomps stripped but its probably useable

otherwise its just gonna sit in a box of other shit on my shelf for a decade

PM if interested

Re: Need advice for Sachs exhaust leak

Chris Thornton /

i know this is an older post but im just looking to confirm that its ok to fill in that gap between the exhaust flange and the port right?mine also drops about 1mm,there seems to be 2 clips in the exhaust port that holds the flange in and was thinking maybe try and push them apart more to stop the flange from dropping and creating an air leak.or maybe some jb weld around it to hold it in place.

Re: Need advice for Sachs exhaust leak

Dan (high idle) Conway /

Chris, grab some springs, and a U clamp that fits the header. drill 2 holes on the opposing cooling fins to hold the springs, and the other side to the U pipe/clamp.

This method is a great permanent fix and prevents the exhaust falling off from a loose header. Many people do this for their sachs.

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