Aftermarket Xj750 Exhaust header,collets

My bike came with a 4-2 Mac megaphone type exhaust. I disassembled to reseal open weld( noisy exhaust). Reassembly requires cleaning the 8-18mm collets, or buying new if really bad. The collets by themselves are hard to find. I found 4pr from 3 diff vendors.

I am looking for a low profile way to clamp the collets tightly to the header, so when tightening the Collar, the header seals against the new gaskets. Even a piece of twisted wire might do the trick.
Cause....
There is just a 1-2mm lip on these headers, and I am finding the collets will Easily slip over the 'lip' as you tighten collar nuts.
Header wont be against the gasket, leaving a loose header end, gap, and noise.
I am trying some clamps(hose clamps are too fat), or maybe a thin cinch clamp to go around ea pair of collets to secure and prevent opening and slipping up and over header lip.
Any help is appreciated.

 

I would measure the OD of the Mac head tubes, then find (muffler shop) some tubing that will fit over that OD (close fit). Then cut a very short length maybe 1/4" and weld them over the Mac head tubes.
To do this you'll have to grind/file the Mac head tubes to remove the too small flange (that doesn't hold anyway). Then finish the end so the gasket can seal the header to the exhaust port.
I just built some 4/1 headers and I had a similar problem.
Cheers, 50gary

 

Will do! I thought I might be making a trip to muffler shop ....

 

Did you permanently leave the stock collar on header? Or are you still using collets?

 

Yes, permanently, in the photo I have them taped so they don't slide down the tubes and scratch the finish. I made the four "slugs" as I call them, the pieces that mate the header tube to the exhaust post face. I have access to a lathe.
I had to modify the header clamps (enlarge the holes) because I used larger than stock diameter tubing. They are mild steel 0.065" wall thickness,
ceramic coated titanium color. Measure carefully, the exhaust studs are only so long so your muffler shop pieces will have to be quite short. What O. D. are your MAC header tubes?
Cheers, 50gary

 

I had a system that had the small flanges. Vibration eventually killed them, cracked them off and rendered the system useless.
I ended up welding (or paid somebody to TIG them) the collars onto the ends, but that system was only made of thin mild steel and didn't last much longer anyway, which is why I only fit stainless pipes of decent thickness since then, as I got so fed up with it.
As a stopgap, you could try holding the collars in place with a wrap of security wire, if it will fit under the collar. It's only to hold them in place until you tighten them up, so it might work.

 

Engine side of flanged header is 40mm, matching the OD of the new Gaskets. I used thin electrical tape to hold the collets in place, otherwise you'll drop crap everywhere. Not enough beer or whiskey will help..

The exhaust port 'rescess' cant be more than a 2mm wider than 40mm

. On my 81 xj750 you couldn't get a "fatter" tube in. If the header tube flange or collet pair is even a little wider, the header will not nest into the port, ending with a loose gasket and no seal. I could feel them seat briefly, but at the same time you're tryng to keep the gasket/collets from falling out, while grabbing a nut to put pressure on seal.

Btw...not all collets are the same. I had to cut mine to 18mm. Many come at 26mm, and may be a heavier gauge steel, which needs to be 'thinned' . The one good point of cutting the collet back is creating fresh metal edge to "grab" the barely there header flange. We wouldn't need these collets if the aftermarket had simply created the orig design. Why is 'simpler' (1 into 2,4 into 1) not better or simpler.

I also just found out the exhaust end baffle canisters(72mm at one end, 98-100mm at other), are not being made, we will have to find someone to fab...not hard but annoying. They run $65 ea. Repacking mine now.

I may just open a 'birthday registry' asking for xj pipes and exhaust for holiday gifts.